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  • 1.
    Eckerström-Liedholm, Simon
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Kotrschal, Alexander
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology.
    Rowiński, Piotr
    Stockholm University, Faculty of Science, Department of Zoology.
    Gonzalez-Voyer, Alejandro
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Fast life-histories are associated with larger brain size in killifishesManuscript (preprint) (Other academic)
    Abstract [en]

    Comparative studies suggest a negative relationship between pace of life-history, and relative energetic investment into brain size. However, since brain size typically evolves as a correlated response to selection on body size, any lag in brain size evolution will result in a shift in relative brain size (e.g. small body – large relative brain size).Coevolution between body size and life-history hence has the potential to drive secondary associations between relative brain size and life-history, when body size is correlated with life history. However, as far as we know, the relationship between relative brain size and life-history strategy has not been examined in systems that simultaneously present marked contrasts in life-history but no concordant shifts in body size. Using a common garden approach, we test the association between relative brain size and life-history in 21 species of killifish; a study system that fulfils the aforementioned requirements. Contrary to the prediction that brain size evolves through energetic trade-offs with life-history, we found that adults, but not juveniles, of fast-living species had larger relative brain sizes. Rather than an energetic link to life-history, our results suggest that fast- and slow-living species differ in terms of how cognitively demanding environments they inhabit are, or alternatively in the ontogenetic timing of somatic vs. neural growth.

  • 2. Johnsson, Jörgen I.
    et al.
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology. University of South Bohemia in České Budějovice, Czechia.
    Studying behavioural variation in salmonids from an ecological perspective: observations questions methodological considerations2018In: Reviews in Fish Biology and Fisheries, ISSN 0960-3166, E-ISSN 1573-5184, Vol. 28, no 4, p. 795-823Article, review/survey (Refereed)
    Abstract [en]

    Salmonid fish are an ecologically important and extensively studied group of fish which concern many interest groups in our society. The aim of this paper is to discuss and suggest solutions to the multifaceted problems associated with studying behavioural variation in salmonids, with focus on designing behavioural studies that are ecologically relevant. Many of the general problems and solutions discussed can be applied to other animals as well. First, the importance of asking clear questions when conceiving behavioural studies is addressed, using Tinbergen's four questions and associated theories as stepping stones towards generating testable hypotheses about behavioural variation. We then address a range of methodological challenges encountered when attempting to study behavioural variation in salmonids and suggest solutions to overcome these problems. A range of approaches is discussed, from highly controllable laboratory experiments to monitoring studies of behaviour in the wild. The importance of combining lab- and field approaches to evaluate the ecological relevance of behavioural variation is highlighted. Finally, we suggest a general framework using a multi-faceted research approach to address questions about the behavioural ecology of salmonids (and other animals) so that knowledge can progress, and the ecological relevance of behavioural studies can be validated.

  • 3. Landeira-Dabarca, A.
    et al.
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology. University of South Bohemia, Czech Republic; University of Gothenburg, Sweden.
    Johnsson, J. I.
    Alvarez, M.
    Cue recognition and behavioural responses in the three-spined stickleback (Gasterosteus aculeatus) under risk of fish predation2019In: Acta Ethologica, ISSN 0873-9749, E-ISSN 1437-9546, Vol. 22, no 3, p. 209-221Article in journal (Refereed)
    Abstract [en]

    To effectively respond to predation risk, prey must assess the risk associated with different predation cues. Predation cues can stem either from the predator or from conspecifics and indicate different predation risk levels, thus eliciting different anti-predation responses. The three-spined stickleback is a well-studied fish species often found in gregarious formations. Previous studies show that sticklebacks perform a variety of anti-predation behaviours; however, little is known about how they respond to multiple simultaneous predator cues, characteristic of heterogeneous natural habitats. Here, we experimentally compare the relative importance of three types of predation cues (visual predator cue, chemical predator odour cue and chemical alarm cue from injured conspecifics) and their interactions, on anti-predation and foraging behaviour of sticklebacks. Results showed that (1) individual sticklebacks responded most strongly to visual predator cues, which resulted in reduced foraging activity, increased spine erection and increased predator inspection; (2) the presence of chemical cues (predator odour and/or conspecific alarm cues) stimulates freezing behaviour to a minor extent; and (3) anti-predation behaviour manifests as a trade-off with foraging-related activities. Overall, the results indicate that sticklebacks could assess risk and modify their behavioural responses depending on which cues are present in the environment. The experimental approach of using factorial combinations of different predatory cues can increase our understanding of the role of multimodal cues in aquatic ecosystems.

  • 4.
    Näslund, Joacim
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Lundgren, Markus
    Mapping the distribution of scale-rayed wrasse Acantholabrus palloni in Swedish Skagerrak using angling records2018In: PeerJ, ISSN 2167-8359, E-ISSN 2167-8359, Vol. 6, article id e5900Article in journal (Refereed)
    Abstract [en]

    In this paper, we map the distribution of scale-rayed wrasse Acantholubrus palloni in eastern Skagerrak based on a combination of verified and personally communicated angling records. Long thought to be occasional vagrants outside its known range in the eastern Atlantic Ocean and Mediterranean Sea, we ask if this rare and understudied labrid has expanded its range and become established in Swedish waters. A recent surge in verified angling records in the Swedish Anglers Association's specimen database Storfiskregistret provides information to suggest that this species should no longer be considered an occasional guest, but rather a species established in the Swedish parts of Skagerrak. These records are supported by additional personal communications with anglers. The species is currently well spread geographically along the Swedish Skagerrak coast, with many locations providing repeated captures of adult fish over multiple years. The typical Swedish catch sites are rocky reefs located between the general 40- and 80-m depth curves, likely influenced by currents bringing higher-salinity water from the North Sea. The present study show that angling records can provide an important, but underutilized, resource for mapping the distribution of data-deficient fish species.

  • 5.
    Näslund, Joacim
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Gothenburg, Sweden.
    Rosengren, Malin
    Johnsson, Jörgen I.
    Fish density, but not environmental enrichment, affects the size of cerebellum in the brain of juvenile hatchery-reared Atlantic salmon2019In: Environmental Biology of Fishes, ISSN 0378-1909, E-ISSN 1573-5133, Vol. 102, no 5, p. 705-712Article in journal (Refereed)
    Abstract [en]

    This paper describes a study on the environmentally dependent brain size plasticity in hatchery-reared Atlantic salmon Salmo salar L. Using a factorial experimental design, we tested whether tank fish density, local hatchery standard (150 fish . m(-2)) vs. reduced (50 fish . m(-2)) and structural enrichment, a bundle of submerged plastic stripes, had effects on the size of the cerebellar region of the brain. Fish reared at reduced density had smaller cerebella, while structural enrichment had no detectable effects. The density effect on cerebellum, which is involved in locomotion and cognition, confirms previous results from hatchery-reared Atlantic salmon. The lack of detectable positive effects of enrichment, which contrasts some previous studies, provide further evidence for a complex relationship between environmental complexity and brain growth.

  • 6.
    Rowiński, Piotr
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Eckerström-Liedholm, Simon
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    The evolution of a placenta is not linked to increased brain size in poeciliid fishesManuscript (preprint) (Other academic)
    Abstract [en]

    Maternal investment traits are considered to have a direct influence on the size of energetically costly organs, including the brain. In placental organisms, offspring are supplied with nutrients during pre-natal development, which in turn may modulate brain size evolution. While this hypothesis has received some support in mammals (i.e. in the marsupial/placental transition), how the evolution of the placenta affects brain size in other taxa is largely unknown.Here, we use eight poeciliid fish species to test if species with placental transferred nutrients, invest more resources into offspring brain development than species with no placental structures. We predicted that the evolution of the placenta would be associated with larger relative brain size in fry, and possibly also shallower ontogenetic brain size allometry, if cognitive demands are similar in adults across placental and non-placental species. We tested these hypotheses by taking non-invasive brain size measurements during the first four weeks of life, and relating these to corresponding somatic growth. Contrary to our expectations, we did not find any differences in brain size between the two maternal strategies. Furthermore, we did not find any differences in how relative brain size changed over ontogenetic development between placental and non-placental species. Elsewhere, maternal investment traits have been commonly linked to brain size, however the species investigated here only exhibit pre-natal provisioning, which may reduce the potential for maternal investment into brain size. Our results suggest that coevolution between placental structures and juvenile brain size is not a general pattern.

  • 7.
    Rowiński, Piotr
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology.
    Eckerström-Liedholm, Simon
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Variation in developmental rates is not linked to environmental unpredictability in annual killifishesManuscript (preprint) (Other academic)
    Abstract [en]

    Comparative evidence suggests that adaptive plasticity may evolve as a response to predictable environmental variation. However, receiving less attention is unpredictable environmental variation, which is considered to affect evolutionary trajectories by increasing phenotypic variation (bet-hedging). If increased variance in development time evolved as an adaptation to unpredictable environmental conditions, we would expect species inhabiting locations with unpredictable conditions to have a higher variance in development time. Here, we examine the occurrence of bet-hedging in egg developmental rate in seven species of annual killifish, originating from a gradient of precipitation rate variation, under three different incubation temperatures (21°C, 23°C, and 25°C). These fish species persist as dormant eggs buried in the soil, in seasonal environments with regular habitat desiccation. At the onset of the rainy season, the eggs must be sufficiently developed in order to hatch, and complete their life-cycle. We found substantial differences among species in both mean and variation of egg development rates, as well as species-specific plastic temperature responses. However, there was no clear relationship between variation in egg development time and variation in precipitation (environmental predictability). Hence, if species specific variances are adaptive, they do not diverge in accordance with simple linear relationship to variation in precipitation.

  • 8. Zavorka, L.
    et al.
    Brijs, J.
    Wengstrom, N.
    Wallerius, M. L.
    Näslund, Joacim
    Stockholm University, Faculty of Science, Department of Zoology.
    Koeck, B.
    Aldven, D.
    Lassus, R.
    Hojesjo, J.
    Johnsson, J. I.
    Cucherousset, J.
    Laboratory captivity can affect scores of metabolic rates and activity in wild brown trout2019In: Journal of Zoology, ISSN 0952-8369, E-ISSN 1469-7998, Vol. 307, no 4, p. 249-255Article in journal (Refereed)
    Abstract [en]

    Phenotypic scoring of wild animals under standardized laboratory conditions is important as it allows field ecologists and evolutionary biologists to understand the development and maintenance of interindividual differences in plastic traits (e.g. behaviour and physiology). However, captivity is associated with a shift from a natural familiar environment to an unfamiliar and artificial environment, which may affect estimates of plastic phenotypic traits. In this study, we tested how previous experience with laboratory environments and time spent in captivity affects behavioural (i.e. activity) and metabolic (i.e. standard and maximum metabolic rates) scoring of our model species, wild brown trout Salmo trutta. We found that individuals with previous experience of laboratory captivity (10.5 months earlier) showed higher activity in an open field test than individuals with no prior experience of laboratory captivity. Previous experience with captivity had no significant effect on metabolic rates. However, metabolic rates seemed to increase with increasing time spent in captivity prior to the collection of measurements. Although there are benefits of keeping wild animals in captivity prior to scoring, our results suggest that while allowing for sufficient acclimatization researchers should aim at minimizing time in captivity of wild animals to increase accuracy and ecological relevance of the scoring of plastic phenotypic traits.

1 - 8 of 8
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