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  • 1. Andersson, J.
    et al.
    Dahl, J.
    Johansson, A.
    Karås, P.
    Nilsson, J.
    Sandström, O.
    Svensson, P. Andreas
    Utslagen fiskrekrytering och sviktande fiskbestånd i Kalmar läns kustvatten. (English title: Recruitment failure and decreasing fish stocks in the coastal areas of Kalmarsund.)2000Rapport (Fagfellevurdert)
  • 2. Barber, I.
    et al.
    Svensson, P. A.
    Effects of experimental Schistocephalus solidus infections on growth, morphology and sexual development of female three-spined sticklebacks, Gasterosteus aculeatus2003Inngår i: Parasitology, ISSN 0031-1820, E-ISSN 1469-8161, Vol. 126, s. 359-367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of naturally infected hosts in studies attempting to identify parasite-induced changes in host biology is problematical because it does not eliminate the possibility that infection may be a consequence, rather than a cause, of host trait variation. In addition, uncontrolled concomitant infections may confound results. In this study we experimentally infected individual laboratory-bred female three-spined sticklebacks Gasterosteus aculeatus L. with the pseudophyllidean cestode Schistocephalus solidus [Muller], and compared the morphology and growth patterns of infected females with sham-exposed controls over a 16-week period. Fish were fed a ration of 8% body weight per day. Non-invasive image analysis techniques allowed the growth of individual plerocercoids to be tracked in vivo throughout the course of infection, and patterns of host and parasite growth were determined. Females that developed infections diverged morphometrically from unexposed control females and exposed-uninfected females at 6 weeks post-infection, with the width of the body at the pectoral fins giving the earliest indication of infection success. When including the plerocercoid, infected females gained weight more quickly than controls, but when plerocercoid weight was removed this trend was reversed. There was no effect of infection on the increase in fish length. Plerocercoids grew at different rates in individual hosts, and exhibited measurable sustained weight increases of up to 10% per day. Final estimates of plerocercoid weight from morphometric analysis prior to autopsy were accurate to within +/-17% of actual plerocercoid weight. At autopsy, infected female sticklebacks had significantly lower perivisceral fat reserves but had developed significantly larger ovaries than controls. The results are discussed in relation to previous studies examining natural infections, and the value of utilizing experimental infections to examine ecological aspects of host-parasite interactions is discussed.

  • 3. Barber, I.
    et al.
    Svensson, P. Andreas
    Synchrony between parasite development and host behaviour change2003Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 63 Supp A, s. 246-Artikkel i tidsskrift (Fagfellevurdert)
  • 4. Barber, I.
    et al.
    Walker, P.
    Svensson, P. A.
    Behavioural responses to simulated avian predation in female three spined sticklebacks the effect of experimental Schistocephalus solidus infections2004Inngår i: Behaviour, ISSN 0005-7959, E-ISSN 1568-539X, Vol. 141, s. 1425-1440Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Plerocercoid larvae of Schistocephalus solidus are common parasites of three-spined sticklebacks that require the ingestion of stickleback hosts by birds to complete their life cycle. Amongst wild-caught sticklebacks, infection is associated with a reduction in antipredator behaviour; however, to date no study has examined the escape responses of experimentally infected sticklebacks, and thus assigning causality remains difficult. Here, we compare aspects of the antipredator behaviour of five experimentally infected female sticklebacks with shamexposed controls over a 16 post-exposure week period. During weeks 1-7 post-exposure, the escape responses of infected fish did not differ significantly from those of sham-exposed fish. However, over weeks 9-15, when infected fish had developed plerocercoids of >50 mg—the size at which they become infective to birds —a lower proportion of infected fish performed directional responses and reached cover within 2 s of the strike. Infected fish also performed a lower frequency of ‘staggered dashes’, and a higher frequency of ‘slow swims’, than shamexposed fish over weeks 9-15. Amongst sham-exposed fish, re-emergence from cover was uncommon throughout the study, but infected fish regularly left cover during weeks 9-15. Our results support those of previous studies examining behavioural change in naturally infected fish and, although other explanations remain possible, our finding that behaviour change in experimentally-infected fish is limited to hosts harbouring single infective parasites provides further evidence that the behaviour changes may be parasite adaptations.

  • 5.
    Brüsin, Martin
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Svensson, P. Andreas
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Hylander, Samuel
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Individual changes in zooplankton pigmentation in relation to ultraviolet radiation and predator cues2016Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 61, nr 4, s. 1337-1344Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Copepods are common crustaceans in aquatic systems and one of the most important producers of carotenoidastaxanthin pigments, which can enhance the animals’ resistance against potentially damaging ultraviolet radiation (UVR), but at the same time, increases the risk of fish predation. Previous studies have demonstrated that copepods have different pigmentation levels matching the current threat level in terms of UVR and fish occurrence. However, these other studies have quantified population-levels changes in pigmentation, making it difficult to disentangle the role of individual phenotypic colour changes from that of selection.We quantified carotenoid-based pigmentation with colorimetric methods, which enabled us to track changes within individual copepods. Two species of copepods, Diaptomus castor and Eudiaptomus gracilis, were exposed to high and low UVR and fish cues in a factorial design. L*a*b* colour values (CIE; CommissionInternational de l’Eclairage) were extracted from digital photographs of each copepod and used as proxies for carotenoid concentration. Our results showed that individual copepods significantly changed their pigmentation in response to both UVR and fish cues within a period of 2 weeks. However, the responses differed between sexes and between adults and juveniles. UVR effects were present in all life-stages whereas fish effects were only detected in juveniles, with largest responses in D. castor. This confirms that carotenoid pigmentation is a phenotypically plastic trait, and highlights that strategies for trading off risks of UVR and predation differ between males and females as well as between life-stages.

  • 6. Eklund, B.
    et al.
    Svensson, A. P.
    Jonsson, C.
    Malm, T.
    Toxic effects of decomposing red algae on littoral organisms2005Inngår i: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 62, nr 4, s. 621-626Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large masses of filamentous red algae of the genera Polysiphonia, Rhodomela, and Ceramium are regularly washed up on beaches of the central Baltic Sea. As the algal masses start to decay, red coloured effluents leak into the water, and this tinge may be traced several hundred meters off shore. In this study, possible toxic effects of these effluents were tested on littoral organisms from different trophic levels. Effects on fertilisation, germination and juvenile survival of the brown seaweed Fucus vesiculosus were investigated, and mortality tests were performed on the crustaceans Artemia salina and Idotea baltica, as well as on larvae and adults of the fish Pomatoschistus microps. Fucus vesiculosus was the most sensitive species of the tested organisms to the red algal extract. The survival of F. vesiculosus recruits was reduced with 50% (LC50) when exposed to a concentration corresponding to 1.7 g l(-1) dw red algae. The lethal concentration for L baltica, A. salina and P. microps were approximately ten times higher. The toxicity to A. salina was reduced if the algal extract was left to decompose during two weeks but the decline in toxicity was not affected by different light or temperature conditions. This study indicates that the filamentous red algae in the central Baltic Sea may produce and release compounds with negative effects on the littoral ecosystem. The effects may be particularly serious for the key species F. vesiculosus, which reproduce in autumn when filamentous red algal blooms are most severe. (C) 2004 Elsevier Ltd. All rights reserved.

  • 7. Engkvist, R.
    et al.
    Malm, T.
    Svensson, A.
    Asplund, L.
    Isaeus, M.
    Kautsky, L.
    Greger, M.
    Lanberg, T.
    Makroalgsblomningar längs Ölands kuster, effekter på det lokala näringslivet och det marina ekosystemet. (English title: Macro algal blooms in the central Baltic proper, effects on the economy and the marine ecosystem.)2001Rapport (Fagfellevurdert)
  • 8.
    Flink, Henrik
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Behrens, Jane W.
    Tech Univ Denmark, Denmark.
    Svensson, P. Andreas
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Consequences of eye fluke infection on anti-predator behaviours in invasive round gobies in Kalmar Sound2017Inngår i: Parasitology Research, ISSN 0932-0113, E-ISSN 1432-1955, Vol. 116, nr 6, s. 1653-1663Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Larvae of the eye fluke, Diplostomum, emerge from snails and infect fish by penetrating skin or gills, then move to the lens where they may impair the vision of the fish. For the fluke to reproduce, a bird must eat the infected fish, and it has been suggested that they therefore actively manipulate the fish's behaviour to increase the risk of predation. We found that round gobies Neogobius melanostomus, a species that was recently introduced to the Kalmar Sound of the Baltic Sea, had an eye fluke prevalence of 90-100%. We investigated how the infection related to behavioural variation in round gobies. Our results showed that the more intense the parasite-induced cataract, the weaker the host's response was to simulated avian attack. The eye flukes did not impair other potentially important anti-predator behaviours, such as shelter use, boldness and the preference for shade. Our results are in accordance with the suggestion that parasites induce changes in host behaviour that will facilitate transfer to their final host.

  • 9.
    Flink, Henrik
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Svensson, P. Andreas
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Nest size preferences and aggression in sand gobies (Pomatoschistus minutus)2015Inngår i: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 69, nr 9, s. 1519-1525Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In animal competition, resource holding potential (RHP) and resource value are two important factors determining the level of aggression and the outcome of contests. One valuable resource among nest-brooding animals that is subject to intense competition is a suitable nest substrate. Sand goby males (Pomatoschistus minutus) rely on finding good nest substrates, but the strategies vary between regions. We first investigated the nest size preferences in sand gobies from Kalmar Sound, a brackish area of the Baltic Sea with a shortage of suitable shells for nest construction and few invertebrate nest predators. Males expressed clear preference for larger nest substrates regardless of the male’s own size. To manipulate resource value, we provided males with large or small nests and tested if this and/or RHP affected aggression during nest defence. Resource value (a preferred large nest vs an unpreferred small nest) had no effect on aggression. However, RHP (total length of the resident male) had a significant effect. Larger males were more aggressive than smaller ones when matched against an opponent of the same size, suggesting that resident males acted according to own RHP.

  • 10. Guevara-Fiore, P.
    et al.
    Svensson, P. Andreas
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
    Endler, J.A.
    Sex as moderator of early life experiences: interaction between rearing environment and sexual experience in male guppies2012Inngår i: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 84, nr 4, s. 1023-1029Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of learning have been neglected in studies of sexual selection because previous researchers have assumed, implicitly or explicitly, that sexual behaviour is genetically fixed. To understand the role of learning in sexual selection, it is important to investigate how early experience interacts with adult experience to determine the use of different mating strategies. We explored this interaction by comparing the sexual behaviour of male guppies, Poecilia reticulata, raised in different social environments before and after they gained sexual experience. Males raised with other males performed long courtship displays at first, but decreased their courtship after they had gained sexual experience. However, for males raised only with females, sexual experience did not modify courtship duration. Males raised exclusively with females exhibited high rates of forced copulation attempts in their first encounter with a female, but reduced this behaviour after sexual experience. In contrast, males raised with other males did not modify their forced copulations. Adult sexual experience appeared to mitigate the behavioural differences caused by variation in rearing environment. Sexual experience helps males to find an optimal balance between courtship displays and forced copulation attempts. We also show that more males exhibited male–male aggression after sexual experience if they had social interactions with other males early in life. This study highlights that courtship and other sexual strategies are not fixed, and that several potential sources of variation exist in the development of an animal's sexual behaviour. Importantly, juvenile and adult experiences can interact to shape sexual behaviour in males.

  • 11. Isaeus, M.
    et al.
    Malm, T.
    Persson, S.
    Svensson, A.
    Effects of filamentous algae and sediment on recruitment and survival of Fucus serratus (Phaeophyceae) juveniles in the eutrophic Baltic Sea2004Inngår i: European journal of phycology, ISSN 0967-0262, E-ISSN 1469-4433, Vol. 39, nr 3, s. 301-307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Eutrophication of the Baltic Sea has increased both the growth of annual filamentous algae and the rate of sedimentation. Together these factors may have a detrimental effect on the survival of perennial macroalgal populations. The aim of this research was to study how these factors affect the colonization success of Fucus serratus at the local level. We investigated the settlement and survival of F. serratus germlings through a combination of field studies and laboratory experiments. The study area lay off the east coast of Oland, along the central Baltic Sea, where consistently-submerged, extensive fucoid stands occur at depths of 2- 10 in, together with turf-forming filamentous algae, mainly Polysiphonia fucoides. Very few F. serratus juveniles were observed outside the sweeping radius of adult F. serratus individuals at a 7-m depth, while abundant recruits were found inside F. serratus stands. Amounts of filamentous algae and sediment were significantly larger outside the F. serratus stands than inside, and the amount of fine sediment (< 0.25 mm) was positively correlated with the amount of filamentous algae, suggesting that fine sediment accumulates in the turf. Experimental studies showed that both filamentous algae and sediment negatively affect the settlement ability of F. serratus eggs and zygotes and the subsequent survival of the germlings, with sediment having the strongest effect. Thus, the prior existence of an adult F. serratus population may allow for continuing recruitment of juveniles, while colonization of new areas unaffected by the sweeping effect of larger individuals seems very difficult under current conditions.

  • 12.
    Lehtonen, Topi K.
    et al.
    Monash Univ, Australia.
    Svensson, P. Andreas
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM). Monash Univ, Australia.
    Wong, Bob B. M.
    Monash Univ, Australia.
    Aggressive desert goby males also court more, independent of the physiological demands of salinity2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikkel-id 9352Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Both between- and within-individual variation in behaviour can be important in determining mating opportunities and reproductive outcomes. Such behavioural variability can be induced by environmental conditions, especially if individuals vary in their tolerance levels or resource allocation patterns. We tested the effects of exposure to different salinity levels on male investment into two important components of mating success-intrasexual aggression and intersexual courtship-in a fish with a resource defence mating system, the desert goby, Chlamydogobius eremius. We found that males that were more aggressive to rivals also exhibited higher rates of courtship displays towards females. Contrary to predictions, this positive relationship, and the consistency of the two behaviours, were not affected by the salinity treatment, despite the physiological costs that high salinity imposes on the species. Moreover, over the entire data-set, there was only a marginally non-significant tendency for males to show higher levels of aggression and courtship in low, than high, salinity. The positive correlation between male aggression and courtship, independent of the physiological demands of the environment, suggests that males are not inclined to make contrasting resource investments into these two key reproductive behaviours. Instead, in this relatively euryhaline freshwater species, typical investment into current reproductive behaviours can occur under a range of different salinity conditions.

  • 13.
    Lehtonen, Topi K.
    et al.
    Monash University, Australia ; University of Turku, Finland.
    Svensson, P. Andreas
    Monash University, Australia ; Deakin University, Australia.
    Wong, Bob B. M.
    Monash University, Australia.
    Both male and female identity influence variation in male signalling effort2011Inngår i: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 11, artikkel-id 233Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Male sexual displays play an important role in sexual selection by affecting reproductive success. However, for such displays to be useful for female mate choice, courtship should vary more among than within individual males. In this regard, a potentially important source of within male variation is adjustment of male courtship effort in response to female traits. Accordingly, we set out to dissect sources of variation in male courtship effort in a fish, the desert goby (Chlamydogobius eremius). We did so by designing an experiment that allowed simultaneous estimation of within and between male variation in courtship, while also assessing the importance of the males and females as sources of courtship variation. Results: Although males adjusted their courtship depending on the identity of the female (a potentially important source of within-male variation), among-male differences were considerably greater. In addition, male courtship effort towards a pair of females was highly repeatable over a short time frame. Conclusion: Despite the plasticity in male courtship effort, courtship displays had the potential to reliably convey information about the male to mate-searching females. Our experiment therefore underscores the importance of addressing the different sources contributing to variation in the expression of sexually-selected traits.

  • 14.
    Lehtonen, Topi K.
    et al.
    Monash Univ, Australia.
    Svensson, P. Andreas
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM). Monash Univ, Australia.
    Wong, Bob B. M.
    Monash Univ, Australia.
    The influence of recent social experience and physical environment on courtship and male aggression2016Inngår i: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 16, artikkel-id 18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Social and environmental factors can profoundly impact an individual's investment of resources into different components of reproduction. Such allocation trade-offs are expected to be amplified under challenging environmental conditions. To test these predictions, we used a desert-dwelling fish, the desert goby, Chlamydogobius eremius, to experimentally investigate the effects of prior social experience (with either a male or a female) on male investment in courtship and aggression under physiologically benign and challenging conditions (i.e., low versus high salinity). Results: We found that males maintained a higher level of aggression towards a rival after a recent encounter with a female, compared to an encounter with a male, under low (but not high) salinity. In contrast, male investment in courtship behaviour was unaffected by either salinity or social experience. Conclusion: Together, our results suggest that male investment in aggression and courtship displays can differ in their sensitivity to environmental conditions and that not all reproductive behaviours are similarly influenced by the same environmental context.

  • 15.
    Lehtonen, Topi K.
    et al.
    University of Konstanz, Germany ; Monash University, Australia; University of Turku, Finland.
    Wong, Bob B. M.
    Monash University, Australia.
    Svensson, P. Andreas
    Monash University, Australia.
    Meyer, Axel
    University of Konstanz, Germany.
    Adjustment of brood care behaviour in the absence of a mate in two species of Nicaraguan crater lake cichlids2011Inngår i: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 65, nr 4, s. 613-619Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In many taxa, parental strategies can vary among individuals. This is especially true in species with biparental care, with males, more often than females, deserting their mates. While there is an abundance of theoretical predictions and empirical data on factors inducing mate abandonment by males, much less is known about what consequences this may have on female behaviour, particularly in the field and in non-avian systems. Here, we compared brood defence rate, behavioural defence types, and brood success of solitary and paired females in two species of Neotropical cichlid fish in their natural habitat. In terms of the rate of territorial aggression towards potential brood predators, solitary females were able to fully compensate in the absence of a male but, in so doing, ended up maintaining smaller territories, which appeared to compromise offspring fitness in at least one of the two species. Hence, our results suggest that even extensive quantitative compensation in parental effort by solitary females may not be enough to ensure adequate qualitative compensation for the lack of male participation, highlighting the importance of distinguishing between these two aspects of compensatory parental care.

  • 16. Mobley, K. B.
    et al.
    Amundsen, T.
    Forsgren, E.
    Svensson, P. Andreas
    School of Biological Sciences, Monash University, Melbourne, VIC 3800, Australia.
    Jones, A.G.
    Multiple mating and a low incidence of cuckoldry for nest-holding males in the two-spotted goby, Gobiusculus flavescens2009Inngår i: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 9, s. 1-10, artikkel-id 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: A major question in behavioural ecology concerns the relationship between genetic mating systems and the strength of sexual selection. In this study, we investigated the genetic mating system of the two-spotted goby (Gobiusculus flavescens), a useful fish model for the study of sexual selection whose genetic mating system remains uncharacterized. We developed four polymorphic microsatellite markers and used them to conduct parentage analyses on 21 nests collected during the breeding season to examine the rates of multiple mating by males and to test for evidence of alternative mating strategies. Results: Results of this study indicate that male G. flavescens mate with multiple females and enjoy confidence of paternity. We detected only one instance of sneaking, so cuckoldry contributed a very small percentage (~0.1%) of the total fertilizations in this population. Nests were nearly full and males that maintain larger nests have higher mating and reproductive success, irrespective of body size. Conclusion: Overall, our investigation shows that G. flavescens is similar to other, related gobies in that the nests of care-giving males often contain eggs from multiple females. However, G. flavescens differs from other gobies in displaying an extremely low rate of cuckoldry. The study of ecological factors responsible for this important difference between G. flavescens and related species should be a fertile area for future work.

  • 17. Nilsson Sköld, H.
    et al.
    Svensson, P. Andreas
    Monash Univ, Sch Biol Sci, Clayton, Vic 3800, Australia.
    Zejlon, C.
    The capacity for internal colour change is related to body transparency in fishes2010Inngår i: Pigment Cell & Melanoma Research, ISSN 1755-1471, E-ISSN 1755-148X, Vol. 23, nr 2, s. 292-295Artikkel i tidsskrift (Fagfellevurdert)
  • 18. Sköld, H. N.
    et al.
    Amundsen, T.
    Svensson, P. Andreas
    Mayer, I.
    Bjelvenmark, J.
    Forsgren, E.
    Hormonal regulation of female nuptial coloration in a fish2008Inngår i: Hormones and Behavior, ISSN 0018-506X, E-ISSN 1095-6867, Vol. 54, nr 4, s. 549-556Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Physiological color change in camouflage and mating is widespread among fishes, but little is known about the regulation of such temporal changes in nuptial coloration and particularly concerning female coloration. To better understand regulation of nuptial coloration we investigated physiological color change in female two-spotted gobies (Gobiusculus flavescens). Females of this species develop an orange belly that acts as an ornament. The orange color is caused by the color of the gonads combined with the chromathophore based pigmentation and transparency of the skin. Often during courtship and female-female competition, a rapid increase in orange coloration, in combination with lighter sides and back that increases skin and body transparency, gives the belly an intense 'glowing' appearance. To understand how this increased orange coloration can be regulated we analysed chromatic and transparency effects of neurohumoral agents on abdominal skin biopsies in vitro. We found prolactin and alpha-melanocyte stimulating hormone (MSH) to increase orange coloration of the skin. By contrast, melatonin and noradrenaline increased skin transparency, but had a negative effect on orange coloration. However, mixtures of melatonin and MSH, or melatonin and prolactin, increased both orange coloration and transparency. This effect mimics the chromatic 'glow' effect that commonly takes place during courtship and intra sexual aggression. Notably, not only epidermal chromatophores but also internal chromatophores lining the peritoneum responded to hormone treatments. There were no chromatic effects of the sex steroids 17 beta-estradiol, testosterone or 11-ketotestosterone. We hypothesize that similar modulation of nuptial coloration by multiple hormones may be widespread in nature. (C) 2008 Elsevier Inc. All rights reserved.

  • 19.
    Svensson, P. Andreas
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    A new goby research lab in the central Baltic Proper2013Konferansepaper (Annet vitenskapelig)
  • 20.
    Svensson, P. Andreas
    Högskolan i Kalmar, Naturvetenskapliga institutionen.
    Adaptations and strategies for paternal care in a desert-dwelling fish. 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Parental care enhances offspring development and survival, but also imposes costs to the caring parent by reducing, for example, future reproduction. This is especially true in species with paternal care, that is, where the male cares for the offspring. Both anatomical and behavioural adaptations are expected to have evolved in order to economize paternal care. The Australian desert goby is a sexually dimorphic species that expresses exclusive paternal care. Males have larger pectoral fins relative to females, possibly to assist in the fanning of the eggs. Males also strategically adjust their parental effort to maximise their fitness. In laboratory experiments, we found that males with larger fins fanned at a lower frequency. The presence of ready-to-spawn females led to a reduction in paternal care effort suggesting a temporal trade-off between care of existing eggs and courtship of additional females. In addition, both the degree and type of filial cannibalism was related to the size of the clutch, and, therefore, female quality. Our results suggest that desert gobies have evolved both morphological adaptations and behavioural strategies to balance the costs and benefits of paternal care.

  • 21. Svensson, P. Andreas
    Beror minskningen av abborre och gädda i Kalmarsund på nedsatt fertilitet? (English title: Poor recruitment of perch and pike in the Kalmarsund, Sweden - is it due to a decreased fertility?)2000Rapport (Fagfellevurdert)
  • 22.
    Svensson, P. Andreas
    Högskolan i Kalmar, Naturvetenskapliga institutionen.
    Female coloration and beneficial egg carotenoids2006Konferansepaper (Fagfellevurdert)
  • 23.
    Svensson, P. Andreas
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
    Female coloration and beneficial egg carotenoids2007Konferansepaper (Annet vitenskapelig)
  • 24.
    Svensson, P. Andreas
    Department of Biology, NTNU, Trondheim.
    Female coloration, egg carotenoids and reproductive success: gobies as a model system2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In two-spotted gobies (Gobiusculus flavescens), females develop an orange belly as they approach sexual maturity. Toward the end of the single breeding season, males become rare and females compete for spawnings. Nest-holding males then prefer females with more colourful bellies and this trait has been suggested to act as a female ornament. I found a positive relationship between belly coloration and the coloration of the underlying gonads. This shows that belly coloration honestly reflects egg pigmentation, mainly because the transparency of the abdominal skin allows other fish to see the gonads directly. The factors contributing to variation in the nuptial coloration of female G. flavescens was examined in a series of investigations (Paper I). When gonads matured they became more colourful while the abdominal skin became more transparent. This caused an increase in nuptial coloration as females approached maturity. However, there was considerable variation in belly coloration also among fully mature females. Mature females had more colourful bellies late in the breeding season, partly due to an increase in gonad carotenoid concentration but also due to a seasonal increase in skin coloration. Analyses of gonads from wild-caught female G. flavescens showed the three main carotenoids to be astaxanthin, idoxanthin and adonixanthin (34%, 23% and 21% of the total carotenoid concentration, respectively). Compared to females of the five other gobiid species found in the same area, G. flavescens had much more colourful bellies. The unique ornamentation of G. flavescens females was achieved by the concurrent exaggeration of all signal components: gonad coloration, skin coloration and skin transparency. To understand how gonad and skin pigmentation interact in the nuptial coloration of female G. flavescens, the role of skin chromatophores was examined in detail (Paper II). Noradrenaline caused aggregation of chromatophore pigment and was used to experimentally reduce the contribution of skin chromatophores to the nuptial coloration. Interestingly, the aggregation of skin pigment weakened the positive relationship between belly and gonad coloration, despite an increase in skin transparency. The results show that female G. flavescens have a potential to use skin chromatophores to rapidly alter their nuptial coloration, thereby affecting the efficacy with which information about gonad coloration is conveyed.  

     

    Carotenoid-based ornamentation has often been suggested to signal mate quality, and species with such ornaments have frequently been used in studies of sexual selection. Carotenoids can be beneficial to animals in various ways, especially during sensitive life stages such as embryonic development. However, empirical work has so far provided equivocal evidence of beneficial effects of carotenoids in vivo. Because males invest heavily in offspring during incubation, the evolution of the male mate preference can be explained if colourful females provide males with eggs of higher quality. This hypothesis was tested by letting males spawn with naturally ‘colourful’ and ‘drab’ females, and comparing several reproductive parameters (Paper III).   

     

    Colourful females produced slightly larger clutches and eggs with significantly higher concentrations of total carotenoids than drab females, but their clutches were not of higher quality. In addition, there were no significant relationships between egg carotenoids and clutch quality. These results call into question a link between female nuptial coloration and offspring quality. In a second study, females were given two diets, differing only in carotenoid concentration (Paper IV). Females given carotenoid- rich feed attained a stronger nuptial coloration, laid more carotenoid-rich eggs and were more likely to spawn. This group also produced larvae that had a stronger phototactic response, suggesting higher offspring quality. This result suggests a direct benefit for males that choose to mate with colourful females. Other measures of reproductive success commonly reported in the literature, such as fertilization rate, hatching success and offspring susceptibility to starvation, were not affected by maternal carotenoid supply.

    In this thesis I have established a link between female ornamentation and egg carotenoid concentration, as well as a relationship between egg carotenoid concentration and offspring quality. The work constitute a uniquely detailed description of factors affecting variation in a nuptial signal and in its different components, and relate these to current theory on signal evolution.  

  • 25.
    Svensson, P. Andreas
    Norwegian University of Science and Technology.
    Female coloration, egg carotenoids and reproductive success gobies as a model system, PhD Thesis2006Doktoravhandling, med artikler (Annet vitenskapelig)
  • 26.
    Svensson, P. Andreas
    Högskolan i Kalmar, Naturvetenskapliga institutionen.
    Female two-spotted gobies display egg carotenoid status2004Konferansepaper (Annet vitenskapelig)
  • 27.
    Svensson, P. Andreas
    Högskolan i Kalmar, Naturvetenskapliga institutionen.
    Female two-spotted gobies display egg carotenoid status.2004Konferansepaper (Fagfellevurdert)
  • 28.
    Svensson, P. Andreas
    Monash University.
    Gobies and carotenoids2008Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In the thirty years since John Endler's seminal work on guppies, carotenoid based signals have become a large and growing topic in behavioural ecology, especially in birds and fishes. Carotenoids are common pigments in animal signals,but they are also important as antioxidants and provitamins. Their dual role in ornaments and physiology make carotenoids ideally suited for answering questions about honest signalling. However, testing the theoretical predictions is not always straightforward, and properly designed experiments are a rather recent phenomenon. In many birds and fishes, females incorporate large quantities of carotenoids into eggs, but the reasons for this are only partially understood. For example, many species seem to do fine without carotenoids. I will briefly introduce carotenoids in signalling before discussing their role in gobies, based on work in nordic gobies.

  • 29.
    Svensson, P. Andreas
    Högskolan i Kalmar, Naturvetenskapliga institutionen.
    Gobies as biomarkers.2006Konferansepaper (Annet vitenskapelig)
  • 30. Svensson, P. Andreas
    Shoaling decisions in the two-spotted goby,Gobiusculus flavescens. MSc thesis.2000Rapport (Annet vitenskapelig)
    Abstract [en]

    Shoaling behavior of young-of-year Gobiusculus flavescens was studied in the lab and in the field outside Kristineberg Marine Research Station, in the Gullmar fjord, Sweden. Natural shoals varied in size from a few to several hundred fish, and were found to be assorted by body size. The structure of the shoals was very dynamic, and any particular group of individuals was unlikely to stay together for more than a few hours. In aquarium experiments, individual G. flavescens preferred joining a small shoal of conspecifics to being on their own. Also, larger shoals were preferred over smaller shoals. Large fish preferred the company of fish of matching body size. Small fish, however, did not show size assortative preferences. Focal fish showed no significant preference for shoaling with familiar compared to unfamiliar fish, not even under predator threat. The results are discussed in view of theories concerning the adaptive basis of shoaling behavior, such as dilution, confusion and oddity effects.

  • 31.
    Svensson, P. Andreas
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
    Strategic male courtship effort in a desert-dwelling fish.2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Strategic allocation of male mating effort is expected if females vary greatly in reproductive value and/or the costs of mating for males are high. Here, we conducted experiments investigating male signalling effort in the Australian desert goby, Chlamydogobius eremius. Males in this species exhibit elaborate courtship of females and exclusive parental care. In the first experiment, we offered focal males two females presented simultaneously in a dichotomous choice design. We found that males preferentially courted the larger of the two females. We found that the same was also true when, in a second experiment, males were presented with females sequentially. Intriguingly, the order of presentation appeared to be important, with males adjusting their courtship depending on the size of the female encountered previously. Our study highlights male mate choice as an important source of variation in male signalling effort.

  • 32.
    Svensson, P. Andreas
    Högskolan i Kalmar, Naturvetenskapliga institutionen.
    Techniques for incubating and analyzing goby eggs.2006Konferansepaper (Annet vitenskapelig)
  • 33.
    Svensson, P. Andreas
    Deakin Univeristy.
    The interval between sexual encounters affect male courtship tactics.2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Courtship displays can enhance male mating success, but are often costly. Thus, instead of courting all females indiscriminately, males could strategically adjust their signalling effort by directing greater courtship towards females of higher reproductive quality. However, plasticity in male courtship intensity remains a largely neglected aspect of sexual selection. Theory predicts that the expression of such plasticity should depend on both the order, and the rate, with which potential mates are encountered. We tested these predictions in a fish, the Australian desert goby, Chlamydogobius eremius. Males preferentially courted the larger of two simultaneously encountered females, probably because larger females are also more fecund. We then investigated male courtship under different sequential scenarios, that is, presenting one female at a time. We found a "previous female effect", with males adjusting their signalling output based on the size of the female they had encountered previously. However, males did not adjust their courtship in this way when the interval between female presentations was longer. Thus, both variation in mate quality, mate encounter rate and previous experiences affected male reproductive decisions. Our findings underscore the importance of considering temporal aspects of mate encounters when trying to understand how mate selection operates in nature.

  • 34.
    Svensson, P. Andreas
    Monash University.
    The interval between sexual encounters affect male courtship tactics2010Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Courtship displays can enhance male mating success, but are often costly. Thus, instead of courting all females indiscriminately, males could strategically adjust their signalling effort by directing greater courtship towards females of higher reproductive quality. However, plasticity in male courtship intensity remains a largely neglected aspect of sexual selection. Theory predicts that the expression of such plasticity should depend on both the order, and the rate, with which potential mates are encountered. We tested these predictions in a fish, the Australian desert goby, Chlamydogobius eremius. Males preferentially courted the larger of two simultaneously encountered females, probably because larger females are also more fecund. We then investigated male courtship under different sequential scenarios, that is, presenting one female at a time. We found a "previous female effect", with males adjusting their signalling output based on the size of the female they had encountered previously. However, males did not adjust their courtship in this way when the interval between female presentations was longer. Thus, both variation in mate quality, mate encounter rate and previous experiences affected male reproductive decisions. Our findings underscore the importance of considering temporal aspects of mate encounters when trying to understand how mate selection operates in nature.

  • 35.
    Svensson, P. Andreas
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
    Adcock, Jacqui L.
    Endler, John A.
    Quantifying ornamental carotenoids in male guppies, Poecilia reticulata2012Inngår i: 5th International Conference of Poeciliid Biologists (Trinidad and Tobago), 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For over 30 years, the orange spots of male guppies have been an iconic example of carotenoid-based ornamentation. The humble guppy was the first of many model species used to study carotenoids in sexual coloration and it is a favoured text book example of signal evolution. It is therefore rather surprising that few have attempted to identify and quantify the carotenoids present in guppies. With some exceptions (most notably Greg Grether's work), researchers have instead tried to infer pigment concentration from colorimetric techniques such as reflectance spectrophotometry or photography. Three major obstacles exist for accurate biochemical determination the carotenoids present in guppies. First, the small body size means that only miniscule amounts are available for analysis. Second, fish skin carotenoids are esterified and samples therefore require potentially destructive hydrolysis. Third, some of the carotenoids are structurally similar, which poses a challenge for successful separation. We have developed a method to identify and quantify the individual carotenoids in guppy skin by using mild saponifiction followed by normal phase high performance liquid chromatography (NP-HPLC). It provides effective hydrolysis of the carotenoid esters without damage to the pigments and is sensitive enough to quantify the carotenoids in a single skin spot. We also used different photographic techniques to measure coloration of both free-swimming and sedated male guppies to investigate how accurate photographic methods are in estimating carotenoid levels.

  • 36. Svensson, P. Andreas
    et al.
    Barber, I.
    Forsgren, E.
    Shoaling behaviour of the two-spotted goby2000Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 56, nr 6, s. 1477-1487Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Naturally formed shoals of adult Gobiusculus flavescens in a Swedish fjord ranged in size from a few individuals to several hundred fish and were sorted by body size. Shoal composition was highly dynamic and any particular group was unlikely to remain together for more than a few hours. Shoaling tendency of juveniles in laboratory experiments was high, and consistent preferences were demonstrated for numerically larger shoals. Large test fish preferred to associate with shoals composed of large, over shoals composed of small fish, whereas small test fish associated with both size classes equally. The ecological importance of shoaling in small shallow water fish is discussed, and possible mechanisms for the observed patterns are proposed. (C) 2000 The Fisheries Society of the British Isles.

  • 37.
    Svensson, P. Andreas
    et al.
    School of Biological Sciences, Monash University 3800, Clayton,VIC, Australia.
    Blount, J. D.
    Forsgren, E.
    Amundsen, T.
    Female ornamentation and egg carotenoids of six sympatric gobies2009Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 75, s. 2777–2787-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Belly colouration, gonad carotenoid concentration and skin transparency were quantified in gravid Gobiusculus flavescens, as well as in females of five sympatric gobies where belly ornamentation has not been described. Although G. flavescens females did, indeed, have far more colourful bellies than the other species, this could only in part be explained by a high concentration of total gonad carotenoids. Comparable, or occasionally higher, carotenoid levels were found in the gonads of other species. Instead, the unusual ornamentation of G. flavescens arises from a unique combination of carotenoid-rich gonads and a highly transparent abdominal skin.

  • 38.
    Svensson, P. Andreas
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Endler, John A.
    Adcock, Jacqui L.
    Experimentally induced divergence of carotenoid usage in male guppy ornaments2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Females are often believed to use male ornaments as observable indicators of non-observable male traits. However, if signal form (e.g. coloration) is highly flexible, its link to signal content (e.g. quality) should be unreliable. Therefore, it is often implicitly assumed that signals are heavily constrained and relatively stable over generations. One popular illustration of costly ornaments is carotenoid-based colour signals. Recent but indirect evidence suggest that such signals may in fact evolve rapidly, but this has not been tested experimentally. We exposed large replicated populations of guppies (Poecilia reticulata; effective population sizes >1000) to three environmental conditions in a multi-generation experiment. The treatments differed in the spectral composition of ambient light by using colour filters which affected how male colours were percieved. This, in turn, was expected to lead to male coloration divergence between treatments due to female choice. In addition, the filters affected the micro-flora and -fauna, which are dietary sources of ornamental pigments. Male skin carotenoids were analysed after 3 and 5 generations. In this short time, populations had diverged in male coloration and in the carotenoid composition of sexual ornaments. A second experiment disentangled environmental and genetic effects. Our study demonstrates evolutionary innovation in signal traits, and how dietary-driven responses to environmental change can impact sexual ornaments.

  • 39.
    Svensson, P. Andreas
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Endler, John A.
    Adcock, Jacqui L.
    Experimentally induced divergence of carotenoid usage in male guppy ornaments2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Females are often believed to use male ornaments as observable indicators of non-observable male traits. However, if signal form (e.g. coloration) is highly flexible, its link to signal content (e.g. quality) should be unreliable. Therefore, it is often implicitly assumed that signals are heavily constrained and relatively stable over generations. One popular illustration of costly ornaments is carotenoid-based colour signals. Recent but indirect evidence suggest that such signals may in fact evolve rapidly, but this has not been tested experimentally. We exposed large replicated populations of guppies (Poecilia reticulata; effective population sizes >1000) to three environmental conditions in a multi-generation experiment. The treatments differed in the spectral composition of ambient light by using colour filters which affected how male colours were percieved. This, in turn, was expected to lead to male coloration divergence between treatments due to female choice. In addition, the filters affected the micro-flora and -fauna, which are dietary sources of ornamental pigments. Male skin carotenoids were analysed after 3 and 5 generations. In this short time, populations had diverged in male coloration and in the carotenoid composition of sexual ornaments. A second experiment disentangled environmental and genetic effects. Our study demonstrates evolutionary innovation in signal traits, and how dietary-driven responses to environmental change can impact sexual ornaments.

  • 40. Svensson, P. Andreas
    et al.
    Forsgren, E.
    Amundsen, T.
    Nilsson Sköld, H.
    Chromatic interaction between egg pigmentation and skin chromatophores the nuptial coloration of female two-spotted gobies2005Inngår i: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 208, s. 4391-4397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In two-spotted gobies (Gobiusculus flavescens Fabricius 1779), females develop an orange belly as they approach sexual maturity. Bright belly coloration is preferred by males and has been suggested to act as a female ornament. This coloration is unusual in that it originates partly from pigmentation of the abdominal skin but also from strongly pigmented gonads directly visible through the skin. In addition, females have been observed to temporarily become more colourful during courtship and competition. To understand how gonad and skin pigmentation interact in this nuptial coloration, the potential for colour modification via regulation of skin chromatophores was investigated. Noradrenaline caused aggregation of chromatophore pigment and was used to experimentally reduce the contribution of skin chromatophores to the nuptial coloration. Chromatophore pigment aggregation caused bellies to become less colourful and abdominal skin biopsies to become less colourful and more transparent. There was a strong positive relationship between belly coloration and the coloration of the underlying gonads. This shows that belly coloration honestly reflects egg pigmentation, mainly because the transparency of the abdominal skin allows other fish to see the gonads directly. Interestingly, when noradrenaline caused pigment to aggregate and thereby increased the transparency of the skin, the relationship between belly and gonad coloration weakened. We conclude that female G. flavescens have a potential to use skin chromatophores to rapidly alter their nuptial coloration, thereby affecting the efficacy with which information about gonad coloration is conveyed.

  • 41.
    Svensson, P. Andreas
    et al.
    Monash Univ, Sch Biol Sci, Clayton, Vic 3800, Australia.
    Lehtonen, T. K.
    Monash Univ, Sch Biol Sci, Clayton, Vic 3800, Australia.
    Wong, B. B. M.
    Monash Univ, Sch Biol Sci, Clayton, Vic 3800, Australia.
    The interval between sexual encounters affects male courtship tactics in a desert-dwelling fish2010Inngår i: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 64, nr 2, s. 1967-1970Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Courtship displays are often important in determining male mating success but can also be costly. Thus, instead of courting females indiscriminately, males might be expected to adjust their signalling effort strategically. Theory, however, predicts that such adjustments should depend on the rate with which males encounter females, a prediction that has been subject to very little empirical testing. Here, we investigate the effects of female encounter rate on male courtship intensity by manipulating the time interval between sequential presentations of large (high quality) and small (low quality) females in a fish, the Australian desert goby Chlamydogobius eremius. Males that were presented with a small female immediately after a large female reduced their courtship intensity significantly. However, males courted large and small females with equal intensity if the interval between the sequential presentations was longer. Our results suggest that mate encounter rate is an important factor shaping male reproductive decisions and, consequently, the evolutionary potential of sexual selection.

  • 42.
    Svensson, P. Andreas
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
    Lehtonen, Topi K.
    Wong, Bob B. M.
    A high aggression strategy for smaller males2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Male-male conflict is common among animals, but questions remain as to when, how and by whom aggression should be initiated. Factors that affect agonistic strategies include residency, the value of the contested resource and the fighting ability of the contestants. Game-theoretical models often assume that strategies for aggression are conditional and shaped by mutual assessment. We quantified aggression in a fish, the Australian desert goby, <i>Chlamydogobius eremius</i>, by exposing nest-holding males to male intruders. The perceived value of the resource (the nest) was manipulated by exposing half of the residents to sexually receptive females before the trial. We found resident male aggression to be unaffected by perceived mating opportunities. It was also unaffected by the size of the intruder. Instead, aggression was related the residents' own size, namely, smaller males attacked sooner and with greater intensity than larger males. Thus, contrary to theory, resident desert goby males appeared to have set strategies for initiating aggression. Rather than viewing high aggression in small males as a paradox (i.e. the Napoleon effect), we suggest that small individuals may benefit from attacking early, before an intruder has time to assess the resident and/or the resource.

  • 43.
    Svensson, P. Andreas
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV. Monash University, Australia.
    Lehtonen, Topi K.
    Monash University, Australia ; University of Turku, Finland.
    Wong, Bob B. M.
    Monash University, Australia.
    A high aggression strategy for smaller males2012Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, nr 8, artikkel-id e43121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Male-male conflict is common among animals, but questions remain as to when, how and by whom aggression should be initiated. Factors that affect agonistic strategies include residency, the value of the contested resource and the fighting ability of the two contestants. We quantified initiation of aggression in a fish, the desert goby, Chlamydogobius eremius, by exposing nest-holding males to a male intruder. The perceived value of the resource ( the nest) was manipulated by exposing half of the residents to sexually receptive females for two days before the trial. Resident male aggression, however, was unaffected by perceived mating opportunities. It was also unaffected by the absolute and relative size of the intruder. Instead resident aggression was negatively related to resident male size. In particular, smaller residents attacked sooner and with greater intensity compared to larger residents. These results suggest that resident desert goby males used set, rather than conditional, strategies for initiating aggression. If intruders are more likely to flee than retaliate, small males may benefit from attacking intruders before these have had an opportunity to assess the resident and/or the resource.

  • 44. Svensson, P. Andreas
    et al.
    Malm, T.
    Engkvist, R.
    Distribution and host plant preference of Idotea baltica (Pallas) (Crustacea Isopoda) on shallow rocky shores in the central Baltic Sea2004Inngår i: Sarsia, ISSN 0036-4827, E-ISSN 1503-1128, Vol. 89, nr 1, s. 1-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Partially due to the mass occurrence of the isopod Idotea baltica, the perennial fucoid vegetation in the Baltic Sea has been destroyed over large areas and replaced by filamentous algae. With a combination of field investigations and laboratory experiments, we tested whether I. baltica preferred Fucus serratus to the dominant red alga Polysiphonia fucoides. In the field, the I. baltica density was higher inside F. serratus than P. fucoides patches when measured per unit area, but the situation was reversed if measured per biomass algae. Diet in the field was well correlated with the distribution of the isopods. A large proportion of the isopod faecal pellets collected in the field contained remnants of microalgae, planktonic animals, and bacteria, but the dominating material was always cells from the actual host plant. In a host plant preference experiment, I. baltica distributed evenly between the two host plant types, but the isopods grazed more heavily on F. serratus: We conclude that although F. serratus is the preferred food item in a choice situation, P. fucoides appears to have the potential to support the I. baltica population with food and shelter. A possible relationship between the weak host plant preference and the low stocks of predatory fish is discussed.

  • 45.
    Svensson, P. Andreas
    et al.
    Norwegian Univ Sci & Technol, Dept Biol, NO-7491 Trondheim, Norway .
    Malm, Torleif
    Engkvist, Roland
    Högskolan i Kalmar, Naturvetenskapliga institutionen.
    Distribution and host plant preference of Idotea baltica (Pallas) (Crustacea: Isopoda) on shallow rocky shores in the central Baltic Sea2004Inngår i: Sarsia, ISSN 0036-4827, E-ISSN 1503-1128, Vol. 89, nr 1, s. 1-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Partially due to the mass occurrence of the isopod Idotea baltica, the perennial fucoid vegetation in the Baltic Sea has been destroyed over large areas and replaced by filamentous algae. With a combination of field investigations and laboratory experiments, we tested whether I. baltica preferred Fucus serratus to the dominant red alga Polysiphonia fucoides. In the field, the I. baltica density was higher inside F. serratus than P. fucoides patches when measured per unit area, but the situation was reversed if measured per biomass algae. Diet in the field was well correlated with the distribution of the isopods. A large proportion of the isopod faecal pellets collected in the field contained remnants of microalgae, planktonic animals, and bacteria, but the dominating material was always cells from the actual host plant. In a host plant preference experiment, I. baltica distributed evenly between the two host plant types, but the isopods grazed more heavily on F. serratus. We conclude that although F. serratus is the preferred food item in a choice situation, P. fucoides appears to have the potential to support the I. baltica population with food and shelter. A possible relationship between the weak host plant preference and the low stocks of predatory fish is discussed.

  • 46.
    Svensson, P. Andreas
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
    Nilsson-Sköld, Helen
    University of Gothenburg.
    Skin biopsies as tools to measure fish coloration and colour change2011Inngår i: Skin Biopsy - Perspectives / [ed] Uday Khopkar, InTech, 2011Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 47.
    Svensson, P. Andreas
    et al.
    Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
    Pélabon, C.
    Blount, J. D.
    Forsgren, E.
    Bjerkeng, B.
    Amundsen, T.
    Temporal variability in a multicomponent trait: nuptial coloration of female two-spotted gobies2009Inngår i: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 20, nr 2, s. 346-353Artikkel i tidsskrift (Fagfellevurdert)
  • 48. Svensson, P. Andreas
    et al.
    Pélabon, C.
    Blount, J. D.
    Surai, P. F.
    Amundsen, T.
    Does female nuptial coloration reflect egg carotenoids and clutch quality in the two-spotted goby (Gobiusculus flavescens, Gobiidae)?2006Inngår i: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 20, s. 689-698Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. Carotenoid based ornamentation has often been suggested to signal mate quality and species with such ornaments have frequently been used in studies of sexual selection. 2. FemaleGobiusculus flavescens(two-spotted goby) develop colourful orange bellies during the breeding season. Belly coloration varies among mature females, and previous work has shown nest holding males to prefer females with more colourful bellies. Since males invest heavily in offspring during incubation, the evolution of this preference can be explained if colourful females provide males with eggs of higher quality. 3. We tested this hypothesis by allowing males to spawn with 'colourful' and 'drab' females and comparing parameters including egg carotenoid concentration, clutch size, hatchability and larval viability between groups. We also investigated relationships between egg carotenoid concentration and clutch quality parameters. 4. Eggs from colourful females had higher concentrations of total carotenoids than eggs from drab females. Colourful females produced slightly larger clutches, but no measure of offspring quality differed between the two groups. Belly coloration quantified in photographs prior to spawning was a good predictor of egg carotenoid concentration, but there were no significant relationships between egg carotenoids and the measures of clutch quality. Females with high levels of egg carotenoids spawned slightly earlier, however, possibly because they were more ready to spawn or because of male mate choice. 5. We found that colourful females provided males with slightly larger clutches and eggs that contained more carotenoids, but despite this, the offspring were not of higher quality. Our results call into question the generality of a causal link between egg carotenoids and offspring quality.

  • 49.
    Svensson, P. Andreas
    et al.
    Monash University, Australia.
    Wong, B. B. M.
    Monash University, Australia.
    Carotenoid-based signals in behavioural ecology: a review2011Inngår i: Behaviour, ISSN 0005-7959, E-ISSN 1568-539X, Vol. 148, nr 2, s. 131-189Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carotenoids are among the most prevalent pigments used in animal signals and are also important for a range of physiological functions. These concomitant roles havemade carotenoidbased signals a popular topic in behavioural ecology while also causing confusion and controversy. After a thorough background, we review the many pitfalls, caveats and seemingly contradictory conclusions that can result from not fully appreciating the complex nature of carotenoid function. Current controversies may be resolved through a more careful regard of this complexity, and of the immense taxonomic variability of carotenoid metabolism. Studies investigating the physiological trade-offs between ornamental and physiological uses of carotenoids have yielded inconsistent results. However, in many studies, homeostatic regulation of immune and antioxidant systems may have obscured the effects of carotenoid supplementation. We highlight how carefully designed experiments can overcome such complications. There is also a need to investigate factors other than physiological trade-offs (such as predation risk and social interactions) as these, too, may shape the expression of carotenoidbased signals.Moreover, the processes limiting signal expression individuals are likely different from those operating over evolutionary time-scales. Future research should give greater attention to carotenoid pigmentation outside the area of sexual selection, and to taxa other than fishes and birds.

  • 50.
    Symons, N.
    et al.
    Monash Univ, Sch Biol Sci, Melbourne, Vic 3004, Australia .
    Svensson, P. Andreas
    Monash Univ, Sch Biol Sci, Melbourne, Vic 3004, Australia .
    Wong, B. B. M.
    Monash Univ, Sch Biol Sci, Melbourne, Vic 3004, Australia .
    Do Male Desert Gobies Compromise Offspring Care to Attract Additional Mating Opportunities?2011Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, nr 6, s. e20576-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Males often play a critical role in offspring care but the time and energy invested in looking after young can potentially limit their ability to seek out additional mating opportunities. Recent studies, however, suggest that a conflict between male parental effort and mating effort may not always be inevitable, especially if breeding occurs near the nest, or if parental behaviours are under sexual selection. Accordingly, we set out to experimentally investigate male care and courtship in the desert goby Chlamydogobius eremius, a nest-guarding fish with exclusive paternal care. Despite courtship occurring near the nest, we found that when egg-tending males were given the opportunity to attract additional females, they fanned their eggs less often, engaged in shorter fanning bouts, and spent more of their time outside their nests courting. Our findings highlight the importance of understanding the circumstances under which reproductive tradeoffs are expected to occur and how these, in turn, operate to influence male reproductive decisions.

12 1 - 50 of 54
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