Reproductive Adaptations Research Articles

Feats of Strength

Feats of Strength is well worth reading for any interested student of biology: a pleasurable read and fascinating analysis of amazing examples of biological adaptation. The theme is the central concept of biology itself: the driving force of evolutionary fitness (successful transfer of genes to the next generation). The author, a scientist who obviously loves biology, provides the reader with clear and fascinating examples of evolutionary fitness, along with interesting descriptions of the research behind our understanding of these traits. Further, Lailvaux is clearly interested in asking the question “Why?” – why has this trait evolved – and in developing research methods to find the answer.Each chapter examines a theme of biological fitness (survival and successful reproduction): “Running, Jumping, and Biting,” “Eating and Not Being Eaten,” “Lovers and Fighters,” and so on. Final chapters address the complex question of “nature versus nurture” in evolution and phenotypic expression, as well as applications in understanding human evolution. Examples lead to frequent mental exclamations of “No way!” or a need for the reader to find a family member to read a choice tidbit out loud. The author’s love of biology is evident throughout, as he presents stalk-eyed flies, migrating swifts, mating spiders (a highly risky business for the males), and racing lizards in his overarching discussion of animal adaptation for survival and reproduction. The overarching imperative of reproductive fitness is evident in examples such as the wolverine frog, which fights to the death for reproductive rights by creating claws by “breaking the tips of its own fingers such that sharp broken bones pierce the flesh”; the mantis shrimp, which can break aquarium glass with a snap of its claw; and the cellular structure of snakes’ muscle, which gives them extra strength. Key concepts about evolution are highlighted, including that adaptation is a functional tradeoff (excellence in one trait often comes at a cost to other traits), that organisms must balance their “energy budgets” (every physical or behavioral adaptation has both a benefit and a cost), and that “evolution is a tinkerer.”Lailvaux’s easy, conversational writing style makes his delight in his material obvious. Particularly evident is his interest in observing a phenomenon, asking why, and figuring out how to research the question. His descriptions of research highlight both elegant solutions to research problems (including lizards in mink coats!) and the difficulties of obtaining research results in a true field setting, or in applying results from controlled experiments to conditions outside the laboratory. There are some flaws in this generally excellent presentation. Lailvaux’s descriptions are occasionally marred by analogies to movies or sports that are not necessarily helpfully familiar to the reader. In several instances, the author alludes to videos that clearly demonstrate the phenomenon under discussion, but without specifically naming the video or including the link, leaving an interested reader to hunt through YouTube to find the material. His final chapter on “Mice and Men” is less clearly organized and presented, perhaps as a reflection of the more theoretical and fluid nature of the research involved. Despite these issues, Feats of Strength is an excellent recommendation for any interested student or teacher of biology and the evolutionary process.

Multiple maternal risk-management adaptations in the loggerhead sea turtle (Caretta caretta) mitigate clutch failure caused by catastrophic storms and predators

Maternal risk-management, an extension of r/K selection, is an indispensable tool for understanding the natural selection pressures that shape the evolution of reproduction. Central to the construct of maternal risk-management is its definition of reproductive success as replacement fitness (w = 2), the survival of one breeding daughter to replace the female and one outbreeding son to replace her mate. Here, I apply maternal risk-management as a theoretical framework to explain multiple reproductive adaptations by loggerhead sea turtles nesting on a barrier island off the southern coast of Florida, US, from 1988 to 2004. Extrapolated over a 30-year reproductive span, nesting females averaged 4000–4500 eggs. I show that, rather than “putting all their eggs in one basket,” females divided eggs into 40 clutches of variable size (50–165 eggs). To deposit clutches, females migrated to the barrier island 10–12 times at unpredictable intervals of 2–8 years. Each nesting season, females deposited 1–7 clutches over diversified time intervals at diversified locations on the beach. Despite devastating clutch losses caused by ten catastrophic hurricanes, hundreds of erratic thunderstorms and dozens of predation events during this study, 72% of clutches produced by nesting females on this barrier island were undisturbed—median hatching success for these clutches was an astonishing 92%. I conclude that diversified maternal investments over time and space by nesting females are reproductive adaptations that have successfully offset clutch losses, thus enabling populations of loggerhead females to meet or exceed their reproductive goal of replacement fitness.

Deep-sea anglerfishes (Lophiiformes: Ceratioidei) from off northeastern Brazil, with remarks on the ceratioids reported from the Brazilian Exclusive Economic Zone

Abstract The deep-sea anglerfishes of the suborder Ceratioidei (Lophiiformes) are represented by about 170 valid species with some of the most extraordinary morphological and reproductive adaptations among vertebrates, including extreme sexual dimorphism and male parasitism. Here we report on the diversity and distribution of rare ceratioids collected during the ABRACOS (Acoustics along the BRAzilian COaSt) expeditions off northeastern Brazil and the Fernando de Noronha Ridge (Rocas Atoll, Fernando de Noronha Archipelago, and associated seamounts). Chaenophryne ramifera, Oneirodes anisacanthus, O. carlsbergi, Gigantactis watermani, and unidentified specimens of Caulophryne, Dolopichthys, and Rhynchactis are recorded for the first time in the Brazilian Exclusive Economic Zone. Ceratias uranoscopus, Melanocetus johnsonii, and Chaenophryne draco have their distributions extended in Brazilian waters. Caulophryne, O. anisacanthus, and G. watermani are also recorded for the first time in the western South Atlantic. The specimen of G. watermani reported here represents the third known specimen of the species, and variations of its escal anatomy in relation to the holotype are described. Based on specimens examined and a review of records in the literature, 20 species of the Ceratioidei, in addition to unidentified species of Caulophryne, Dolopichthys, and Rhynchactis, are confirmed in the Brazilian Exclusive Economic Zone.

The genome of Cleistogenes songorica provides a blueprint for functional dissection of dimorphic flower differentiation and drought adaptability.

Summary Cleistogenes songorica (2n = 4x = 40) is a desert grass with a unique dimorphic flowering mechanism and an ability to survive extreme drought. Little is known about the genetics underlying drought tolerance and its reproductive adaptability. Here, we sequenced and assembled a high‐quality chromosome‐level C. songorica genome (contig N50 = 21.28 Mb). Complete assemblies of all telomeres, and of ten chromosomes were derived. C. songorica underwent a recent tetraploidization (~19 million years ago) and four major chromosomal rearrangements. Expanded genes were significantly enriched in fatty acid elongation, phenylpropanoid biosynthesis, starch and sucrose metabolism, and circadian rhythm pathways. By comparative transcriptomic analysis we found that conserved drought tolerance related genes were expanded. Transcription of CsMYB genes was associated with differential development of chasmogamous and cleistogamous flowers, as well as drought tolerance. Furthermore, we found that regulation modules encompassing miRNA, transcription factors and target genes are involved in dimorphic flower development, validated by overexpression of CsAP2_9 and its targeted miR172 in rice. Our findings enable further understanding of the mechanisms of drought tolerance and flowering in C. songorica, and provide new insights into the adaptability of native grass species in evolution, along with potential resources for trait improvement in agronomically important species.

Reproductive adaptations to high densities in social mammals

An overview of population density control in social mammals sets the framework for examining reproductive responses to increasing population densities. We begin by honoring John B. Calhoun who played a major role, starting about 70 years ago, in correcting the conventional wisdom of the time that population control was all about adjusting mortality rates. Reproduction was considered a constant, and emigration was viewed as a component of mortality. His research was mostly on domestic and feral populations of Rattus norvegicus and Mus musculus for which he built complex arenas that could house thousands of inhabitants. In addition, he constructed elaborate living quarters in the alleyways of Baltimore. For the captive populations, he would individually mark all the inhabitants so that he could identify them and observe their behavior. Eight examples of his research publications are described. He was able to document a list of reproduction related behaviors that are the main focus of this essay, and clearly demolish the simplistic notion that reproduction is a constant. A summary of some of the major issues that encompasses the science of population growth and regulation is provided. There follows a series of 19 examples of non-Calhoun publications that cover many more species of social mammals, including humans. A comprehensive list of the many negative adaptations involving reproductive processes are documented for the 27 publications reviewed confirming that in many species reproductive constraints are non-trivial. There follows a brief discussion that attempts to create a cohesive whole for this intellectual adventure.

Male reproductive strategies in two species of spider crabs, Leurocyclus tuberculosus and Libinia spinosa

Reproductive strategies vary according to season length, individual reproductive traits, and factors associated with the social context such as density and sex ratio of the individuals. The social context predicts the intensity of sexual selection due to its effect on mate choice and intra-sexual competition. Moreover, it exacerbates the costs derived from sexual conflict and allows for the existence of alternative reproductive tactics to counteract such costs. However, these mechanisms are still underexplored in many animal taxa. Majoidea “spider crabs” show a diversity of life history, and behavioral and morphological adaptations for reproduction, which have evolved as an outcome of competition to maximize reproductive success. We aimed to analyze in this study, male reproductive strategies through mating behavior under different social contexts, density of individuals, and males size differences in two species of “spider crabs”, Leurocyclus tuberculosus and Libinia spinosa. The experiments were as follows: one female and one male per aquarium (Experiment 1); a female and three males of similar sizes per aquarium (Experiment 2); and a female and three males of distinct sizes per aquarium (Experiment 3). The experiments showed that mating behavior and duration of mate guarding differ between species and among different social contexts. The presence of males with similar or different sizes showed a relevant different behavior, the female copulated with more than one male when males were similar in size (E2), and copulated only with the largest male when males were different in size (E3). In mate guarding, the shape and the use of the chelipeds had an important role: the male of Leurocyclus tuberculosus grasped the female with the chelipeds and did not fight with other males, but the male of Libinia spinosa surrounded the female with the chelipeds and fought with other males. The longest duration of mate guarding was during precopulatory guarding. Precopulatory guarding was present in all the experiments and its duration did not present significant differences among the experiments. However, in both species, the experiments differ in the duration of postcopulatory guarding until spawning. Gonopod morphology revealed important differences between species and are probably associated with sperm competition. The experiments under distinct social contexts linked to the use and shape of the chelipeds and the morphology of the gonopods, could allow to understand the functional significance of the different reproductive strategies.

Repeating Authorial Blackface in Analogous Adaptation of Probably GhostwrittenThe Dark Child

AbstractAfter decades of investigation, leading scholars conclude that the founding novel of francophone African literature was likely written by Europeans. Camara Laye’s The Dark Child (1953) was sold as an autobiography and became the most read African novel in French. The idyllic narrative that African critics accused of colonial apologetics is now accused by Western scholars of being the product of an anti-independence conspiracy supported by François Mitterrand. When claims of ghost-writing were still dismissed as petty African jealousy, Laurent Chevallier relocated Laye’s childhood story to present-day Guinea with an analogous film adaptation that both builds on and parallels the novel. The French director introduces L’enfant noir (1995) not as his own interpretation but that of Laye’s relatives who also act in his film. Although Chevallier sells his story as authentically local, his Eurocentric adaptation of gender, polygamy, and reproduction has provoked accusations of Western plotting against African values.

Ultrastructural and immunocytochemical studies on the olfactory receptor neurons in the Ichthyosaura alpestris

AbstractMorphological and immunohistochemical studies were conducted on the alpine newt Ichthyosaura alpestris, which is representative of the family Salamandridae. The aim of the study was to determine the differences in olfactory organs structural properties, especially in the olfactory epithelium (OE) of the main olfactory chamber (MOC) and the vomeronasal organ (VNO) between breeding and non‐breeding seasons in this species. A change in environments occurs for alpine newts in the course of the annual cycle because of its aquatic adaptations for reproduction. The results confirmed the variability in the shape and size of olfactory organs between breeding and non‐breeding seasons. The presence of the ovoid cells with microvilli at its apical part was determined in the OE of males and females during breeding season. Giant ORNs, a subtype of ciliated ORNs, were observed only during the newt's non‐breeding season. The presence of the ovoid cells during the terrestrial phase was not determined. Thus, its role might be associated with reproduction.

Unravelling the role of epigenetics in reproductive adaptations to early-life environment.

Reproductive function adjusts in response to environmental conditions in order to optimize success. In humans, this plasticity includes age of pubertal onset, hormone levels and age at menopause. These reproductive characteristics vary across populations with distinct lifestyles and following specific childhood events, and point to a role for the early-life environment in shaping adult reproductive trajectories. Epigenetic mechanisms respond to external signals, exert long-term effects on gene expression and have been shown in animal and cellular studies to regulate normal reproductive function, strongly implicating their role in these adaptations. Moreover, human cohort data have revealed differential DNA methylation signatures in proxy tissues that are associated with reproductive phenotypic variation, although the cause-effect relationships are difficult to discern, calling for additional complementary approaches to establish functionality. In this Review, we summarize how adult reproductive function can be shaped by childhood events. We discuss why the influence of the childhood environment on adult reproductive function is an important consideration in understanding how reproduction is regulated and necessitates consideration by clinicians treating women with diverse life histories. The resolution of the molecular mechanisms responsible for human reproductive plasticity could also lead to new approaches for intervention by targeting these epigenetic modifications.

Mating with immunised male mice affects the phenotype of adult progeny.

The life-history theory suggests that parental experience of the environment is passed to offspring, which allows them to adapt to prevailing conditions. This idea is supported from the mother's side, but to a much less extent from the father's side. Here, we investigated the effect of immunising fathers on pre- and neonatal development and on immune and neuroendocrine phenotypes of their offspring in C57BL/6J mice. Nine days before mating, fathers were intraperitoneally injected with the immunogenic protein keyhole limpet hemocyanin (KLH). Females mated with immunised males had less pre-weaning mortality of newborns compared to those mated with control males. Although the antibody response to KLH was similar for the male offspring of control and immunised fathers, the mass indexes of their main immune organs and their androgen response differed significantly. The mass indexes of the thymus and spleen in adult male offspring of immunised fathers were higher compared with the control offspring. The plasma testosterone levels were significantly decreased after KLH administration in the male offspring of control but not of immunised fathers. This was correlated with changes in sperm average path and straight-line velocities. Finally, excitatory neurotransmitters prevailed over inhibitory ones in the amygdala of the progeny of immunised fathers, while in control offspring, the opposite occurred. This is indicative of complex behavioural changes in the offspring of immunised fathers, including sexual ones. Therefore, the paternal experience of foreign antigens modulates the immune and neuroendocrine systems of their progeny, suggesting possible survival and reproductive adaptations to parasitic pressure.

Climate change and maladaptive wing shortening in a long-distance migratory bird

Abstract Contemporary phenotypic trends associated with global change are widely documented, but whether such trends always denote trait optimization under changed conditions remains obscure. Natural selection has shaped the wings of long-distance migratory birds to minimize the costs of transport, and new optimal wing shapes could be promoted by migration patterns altered due to global change. Alternatively, wing shape could vary as a correlated response to selection on other traits favored in a changing environment, eventually moving away from the optimal shape for migration and increasing transport costs. Data from 20 yr of monitoring 2 Common Nightingale (Luscinia megarhynchos) populations breeding in central Spain, where environmental conditions for breeding have deteriorated during recent decades due to increased summer drought, show that birds have reduced wing length relative to body size over the period 1995–2014. However, long-winged nightingales survived their first round-trip migration better, and the shorter the average wing length of individuals, the stronger the survival-associated natural selection favoring longer wings. Maladaptive short wings may have arisen because the mortality costs of migration are outweighed by reproductive benefits accrued by short-winged nightingales in these populations. Assuming that the phenotypic integration of morphological and reproductive adaptations of migratory birds has a genetic basis, we hypothesize that the maladaptive trend towards shorter wings may be a correlated response to selection for moderate breeding investment in drying habitat. Our results provide evidence that contemporary phenotypic change may deviate average trait values from their optima, thereby increasing our understanding of the ecological constraints underpinning adaptation to rapid global change.

Evolutionary Trajectory for the Emergence of Novel Coronavirus SARS-CoV-2.

Over the last two decades, the world experienced three outbreaks of coronaviruses with elevated morbidity rates. Currently, the global community is facing emerging virus SARS-CoV-2 belonging to Betacoronavirus, which appears to be more transmissible but less deadly than SARS-CoV. The current study aimed to track the evolutionary ancestors and different evolutionary strategies that were genetically adapted by SARS-CoV-2. Our whole-genome analysis revealed that SARS-CoV-2 was the descendant of Bat SARS/SARS-like CoVs and bats served as a natural reservoir. SARS-CoV-2 used mutations and recombination as crucial strategies in different genomic regions including the envelop, membrane, nucleocapsid, and spike glycoproteins to become a novel infectious agent. We confirmed that mutations in different genomic regions of SARS-CoV-2 have specific influence on virus reproductive adaptability, allowing for genotype adjustment and adaptations in rapidly changing environments. Moreover, for the first time we identified nine putative recombination patterns in SARS-CoV-2, which encompass spike glycoprotein, RdRp, helicase and ORF3a. Six recombination regions were spotted in the S gene and are undoubtedly important for evolutionary survival, meanwhile this permitted the virus to modify superficial antigenicity to find a way from immune reconnaissance in animals and adapt to a human host. With these combined natural selected strategies, SARS-CoV-2 emerged as a novel virus in human society.

Resource-dependent evolution of female resistance responses to sexual conflict.

Sexual conflict can promote the evolution of dramatic reproductive adaptations as well as resistance to its potentially costly effects. Theory predicts that responses to sexual conflict will vary significantly with resource levels—when scant, responses should be constrained by trade‐offs, when abundant, they should not. However, this can be difficult to test because the evolutionary interests of the sexes align upon short‐term exposure to novel environments, swamping any selection due to sexual conflict. What is needed are investigations of populations that are well adapted to both differing levels of sexual conflict and resources. Here, we used this approach in a long‐term experimental evolution study to track the evolution of female resistance to sexual conflict in the fruit fly Drosophila melanogaster. In resource‐rich regimes, high‐conflict females evolved resistance to continual exposure to males. There was no difference in baseline survival, consistent with the idea that responses evolving under nutritional abundance experienced no trade‐offs with resistance. In the poor resource regimes, the ability of high‐conflict females to evolve resistance to males was severely compromised and they also showed lower baseline survival than low‐conflict females. This suggested high‐conflict females traded off somatic maintenance against any limited resistance they had evolved in response to sexual conflict. Overall, these findings provide experimental support for the hypothesis that evolutionary responses to sexual conflict are critically dependent upon resource levels.

Highly promiscuous paternity in mainland and island populations of the endangered Northern Quoll

AbstractPolyandry is a commonly utilized strategy in mammalian reproductive systems, where females engage in mating with multiple males to increase either the genetic diversity or quality of their offspring. Some species also exhibit male semelparity, a peculiar life‐history trait where all or most males within a population begin to die following mating. The northern quoll (Dasyurus hallucatus) possesses both of these reproductive adaptations, and females of this species may produce up to eight young in a single litter. Here we aimed to quantify whether there was any difference in female quolls’ choice of male sires between two genetically distinct populations located in the Pilbara region of Western Australia (one mainland‐dwelling and one island‐dwelling population). The total parentage exclusion probability was 0.9999 for excluding a candidate parent from parentage, given the genotype of a known mother. Overall, we found that every litter had young resulting from multiple males. In some litters, a different male fathered every offspring. Thus, northern quolls demonstrated a greater level of polyandry than has previously been detected in marsupials. Furthermore, females from the less genetically diverse island population exercised mate choice and preferentially bred with males that were, on average, 20% smaller than a different male randomly sampled from the island. There was no detectable difference with regard to male sire body size in the mainland population, indicating a difference of selective pressures for the two populations.

Reproductive cycle of the tetra Astyanax bimaculatus (Characiformes: Characidae) collected in Amazonian streams

A histological characterization of gonadal development in the tetra Astyanax bimaculatus was performed, aimed at determining its reproductive cycle in streams localized inside the Amazonian forest. Collections were carried out monthly from August 2017 to July 2018 at the Zoobotânica Foundation of Marabá, PA. Collected specimens were weighed and measured, and their gonads and liver were removed and weighed to calculate gonadosomatic and hepatosomatic indexes. Gonads were fixed and treated for routine histology for light microscopy. Materials were stained with toluidine blue and haematoxylin and eosin. The Amazonian A. bimaculatus species presented two reproductive periods in the year, one at the end of the winter season and another during the summer. Females showed an asynchronous development of their oocytes and only two reproductive phases of development were observed during the whole period 'developing' and 'spawning capable'. Males presented cystic spermatogenesis, with an anastomosing tubular testis containing spermatogonia spread along the germinal epithelium (unrestricted spermatogonial). These morphological characteristics are considered phylogenetically more primitive. Male specimens were observed to have five different phases during the period: immature, initial maturation, mid maturation, final maturation and regression. The huge fluctuations in Amazonian streams was observed, in which water volumes varied considerably across seasons, culminating even in total drought. In spite of this, A. bimaculatus could be found during all seasons, showing its impressive reproductive adaptation to its conditions.

First record of a symbiotic relationship between a polyclad and a black coral with description of Anthoplana antipathellae gen. et sp. nov. (Acotylea, Notoplanidae)

The close relationship between a polyclad (Platyhelminthes, Rhabditophora, Polycladida) and the mesophotic Atlantic–Mediterranean black coral Antipathella subpinnata (Ellis & Solander, 1786) (Cnidaria, Hexacorallia, Antipatharia) is herein described for the first time. Worms, up to 50 mm long, are elongated with sparse dorsal papillae, an anterior, ruffled pharynx and caudal, well-separated gonopores. The bulbous vagina is connected to a very elongated Lang’s vesicle, while the male apparatus, hosting a cuticular penis papilla, consists in a muscular interpolated prostatic vesicle, formed by few chambers surrounding the ejaculatory duct, a major seminal vesicle and numerous spermiducal bulbs. These features, as well as the uniqueness of the symbiotic relationship and relative reproductive adaptations, support the description of a new taxon, Anthoplana antipathellae gen. et sp. nov. (Acotylea, Notoplanidae). The observed symbiosis is ascribable to exclusive inquilinism with some parasitic traits. The individuals, living in large numbers on the colonies, are highly cryptic thanks to a characteristic pigmentation and a wrapped habitus. They lay numerous annular yellow cocoons (rigid, nest-like structures containing the fertilised eggs), in single or multiple rows on the distal branches of the coral, temporarily denudated of coenenchyme. The occurrence of the polyclad is consistent with the Atlantic–Mediterranean geographical and bathymetrical distribution of the A. subpinnata forests as demonstrated by the analysed photo archive, and a summer reproductive peak can be hypothesised based on the temporal observations carried out in the study areas.

Female remating rate and pattern of sperm use suggest intense sperm competition in Drosophila antonietae (Diptera: Drosophilidae)

Sperm competition is conceived as a powerful selective force which acts on genes related to reproduction, promoting the evolution of reproductive adaptations and inter-population divergence that may ultimately lead to speciation. Such selective pressure is believed to be particularly strong in species from the Drosophila repleta group since females of most of these species are highly promiscuous. However, sperm competition is determined by many other factors far less explored than female remating rate; consequently, its actual intensity as a selective pressure continues to remain unknown across most taxa. In this paper, we aim to estimate the intensity of sperm competition in Drosophila antonietae, a South American species from the D. repleta group, by means of behavioural and genetic analyses. In sum, our results, while failing to reveal sperm precedence in twice-mated females, show that sperm competition is likely to occur and may strongly reduce males’ reproductive output. In addition, using highly polymorphic microsatellite loci, we confirmed a high incidence of multiple paternity in wild-inseminated females. We discuss the results within an evolutionary context comparing the mating system between D. antonietae and closely related species.

Comparative proteomic analysis of Tibetan pig spermatozoa at high and low altitudes

BackgroundTo illuminate the mechanisms underlying the high-altitude tolerance of Tibetan pig spermatozoa, proteomes of spermatozoa from Tibetan pigs raised in high and low altitudes were compared using a tandem mass tag (TMT)-labeled quantitative proteomics approach.ResultsA total of 77 differentially expressed proteins (DEPs) were identified. Gene Ontology (GO) analysis revealed DEPs that were predominantly associated with the actin cytoskeleton, the tricarboxylic acid (TCA) cycle, and adenosine triphosphate (ATP) metabolism, and were from 12 enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Three subnetworks were significantly enriched and 10 centric proteins were identified by protein-protein interaction (PPI) network analysis. Relative expression levels of the proteins (ATP5H, CYCS, MYH9 and FN1) were confirmed using Western blotting.ConclusionsOur study is the first to use a tandem mass tag (TMT) approach to analyze Tibetan pig spermatozoa, and provides a foundation to understand the mechanisms underlying the reproductive adaptations of Tibetan pigs to high-altitude environments.

Size-selective harvesting fosters adaptations in mating behaviour and reproductive allocation, affecting sexual selection in fish.

The role of sexual selection in the context of harvest-induced evolution is poorly understood. However, elevated and trait-selective harvesting of wild populations may change sexually selected traits, which in turn can affect mate choice and reproduction. We experimentally evaluated the potential for fisheries-induced evolution of mating behaviour and reproductive allocation in fish. We used an experimental system of zebrafish (Danio rerio) lines exposed to large, small or random (i.e. control) size-selective mortality. The large-harvested line represented a treatment simulating the typical case in fisheries where the largest individuals are preferentially harvested. We used a full factorial design of spawning trials with size-matched individuals to control for the systematic impact of body size during reproduction, thereby singling out possible changes in mating behaviour and reproductive allocation. Both small size-selective mortality and large size-selective mortality left a legacy on male mating behaviour by elevating intersexual aggression. However, there was no evidence for line-assortative reproductive allocation. Females of all lines preferentially allocated eggs to the generally less aggressive males of the random-harvested control line. Females of the large-harvested line showed enhanced reproductive performance, and males of the large-harvested line had the highest egg fertilization rate among all males. These findings can be explained as an evolutionary adaptation by which individuals of the large-harvested line display an enhanced reproductive performance early in life to offset the increased probability of adult mortality due to harvest. Our results suggest that the large-harvested line evolved behaviourally mediated reproductive adaptations that could increase the rate of recovery when populations adapted to high fishing pressure come into secondary contact with other populations.

Zooplankton Communities Associated With New and Regenerated Primary Production in the Atlantic Inflow North of Svalbard

The Arctic Ocean is changing rapidly with respect to ice cover extent and volume, growth season duration and biological production. Zooplankton are important components in the arctic marine food web, and tightly coupled to the strong seasonality in primary production. In this study, we investigate zooplankton composition, including microzooplankton, copepod nauplii, as well as small and large copepod taxa, and primary productivity in the dynamic Atlantic water inflow area north of Svalbard in May and August 2014. We focus on seasonal differences in the zooplankton community and in primary productivity regimes. More specifically, we examine how a shift from “new” (nitrate based) spring bloom to a “regenerated” (ammonium based) post bloom primary production is reflected in the diversity, life history adaptations and productivity of the dominant zooplankton. North of Svalbard, the seasonal differences in planktonic communities were significant. In spring, the large copepod Calanus finmarchicus dominated, but the estimated production and ingestion rates were low compared to the total primary production. In summer, the zooplankton community was composed by microzooplankton and the small copepod Oithona similis. The zooplankton production and ingestion rates were high in summer, and probably depended heavily on the regenerated primary production associated with the microbial loop. There was clear alteration from dominance of calanoid copepod nauplii in spring to Oithona spp. nauplii in summer, which indicates different reproductive strategies of the dominating large and small copepod species. Our study confirms the dependence and tight coupling between the new (spring bloom) primary production and reproductive adaptations of C. glacialis and C. hyperboreus. In contrast, C. finmarchicus appears able to take advantage of the regenerated summer primary production, which allows it to reach the overwintering stage within one growth season in this region north of Svalbard. This suggests that C. finmarchicus will be able to profit from the predicted increased primary production in the Arctic, a strategy also recognized in small copepod species such as O. similis. We speculate that the ability of the copepod species to utilize the regenerated summer primary production and microbial food web may determine the winners and losers in the future Arctic Ocean.