Male Sticklebacks Research Articles

A distinct neurogenomic response to a trade-off between social challenge and opportunity in male sticklebacks (Gasterosteus aculeatus).

Animals frequently make adaptive decisions about what to prioritize when faced with multiple, competing demands simultaneously. However, the proximate mechanisms of decision-making in the face of competing demands are not well understood. We explored this question using brain transcriptomics in a classic model system: threespined sticklebacks, where males face conflict between courtship and territorial defence. We characterized the behaviour and brain gene expression profiles of males confronted by a trade-off between courtship and territorial defence by comparing them to males not confronted by this trade-off. When faced with the trade-off, males behaviourally prioritized defence over courtship, and this decision was reflected in their brain gene expression profiles. A distinct set of genes and biological processes was recruited in the brain when males faced a trade-off and these responses were largely non-overlapping across two brain regions. Combined, these results raise new questions about the interplay between the neural and molecular mechanisms involved in decision-making.

Rates of Alloparental Care by Male Stickleback in Natural Lake Populations

Rates of Alloparental Care by Male Stickleback in Natural Lake Populations

Does paternal care influence mate preference? Male and female mating behavior in Threespine Stickleback ecotypes that differ markedly in parental care.

Reproductive isolation can occur due to divergence in sexual selection for particular traits. For example, differences in mate preference associated with body size can play an important role in divergence between groups. The importance of mate preference for population divergence may be influenced by other aspects of a mating system, such as the requirement for parental care. In Nova Scotia, Canada, two ecotypes of marine Threespine Stickleback occur sympatrically: a "common" ecotype wherein males provide parental care, and a "white" ecotype that does not exhibit paternal care. The goal of our study was to examine differences in male mate preference between white and common stickleback males to test the prediction that males who invest more in parental care may be more selective about their mates. Because of the link between size and fecundity in this species, we predict that males that invest in parental care should prefer large females, while males that do not provide care will not exhibit preference for larger female size. We found that common male stickleback preferred larger-bodied females of both ecotypes, while white males showed a preference for larger-bodied common females. Secondarily, we assessed whether females differed in their willingness to mate with males of different sizes and ecotypes. Common female stickleback had a higher response rate toward smaller white males, which may be associated with their relatively high courtship rates. Counter to previous studies on these ecotypes that suggest that mating is completely assortative, interecotype matings occurred in half of the observed spawning events. This observation, coupled with the results that males may prefer females based mainly on size and females respond to males who court more rigorously regardless of their ecotype, may lend insight into recent genetic evidence for hybridization in the wild.

Effect of salinity on nest building behaviour in the nine-spined stickleback Pungitius sinensis.

The authors evaluated the adaptability of male nine-spined sticklebacks (Pungitius sinensis) at three salinity levels (0, 5 and 10psu) by comparing nest building success rates with nest structures. Successful nest building decreased as salinity increased. In addition, nests built in fresh water (i.e., 0 psu) were glued together, whereas those built in brackish water (5 and 10psu) broke easily and fell from the nest site to the gravel bottom. Based on these findings, the authors suggest that P. sinensis adapts to freshwater environments.

Time and dose-dependent impairment of liver metabolism in Gasterosteus aculeatus following exposure to diclofenac (DCF) highlighted by LC-HRMS untargeted metabolomics

Anthropogenic chemicals as emerging contaminants, such as pharmaceuticals, increased worldwide in the environment. This study aimed to apply metabolomics-based approaches on the fish model species three-spined stickleback (Gasterosteus aculeatus) exposed to diclofenac (DCF) to identify toxicity pathways and potential biomarkers. For this purpose, males and females were exposed to a continuous flow of diclofenac solution in laboratory for 21 days, followed by 3 days of depuration, to nominal concentrations of 1 (low) and 100 μg/L (high) of DCF. A methodology based on liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) was employed. Uni- and multivariate statistical analyses were combined to evaluate the modulations of the liver metabolome of G. aculeatus after exposure to DCF. The metabolomics data revealed variations both as a function of time and of the DCF concentration. We observed 2487 altered metabolites, with 1460 and 1027 specific to males and females, respectively. Some of them were significantly impaired by the experimental conditions. However, we showed that several metabolites were impacted by other factors as they were already modulated in the control individuals. The results indicated that the energy metabolism was up-modulated in females and down-modulated in males, with the presence of DCF. The antioxidant system was impacted in males, suggesting oxidative stress in the metabolism, while the immunity system was down-regulated in females following exposure. Moreover, our results revealed 1 and 4 metabolites as potential metabolic biomarkers in male and female sticklebacks, respectively. Among them, the glutaryl-carnitine and the adipoyl-carnitine were putatively identified in females, known to be implicated in the energy metabolism. These 5 metabolites showed to be promising biomarkers since they were early modulated during exposure to the stress and showed a notable trend through time.

Evolution and developmental expression of the sodium-iodide symporter (NIS, slc5a5) gene family: Implications for perchlorate toxicology.

The vertebrate sodium–iodide symporter (NIS or SLC5A5) transports iodide into the thyroid follicular cells that synthesize thyroid hormone. The SLC5A protein family includes transporters of vitamins, minerals, and nutrients. Disruption of SLC5A5 function by perchlorate, a pervasive environmental contaminant, leads to human pathologies, especially hypothyroidism. Perchlorate also disrupts the sexual development of model animals, including threespine stickleback (Gasterosteus aculeatus) and zebrafish (Danio rerio), but the mechanism of action is unknown. To test the hypothesis that SLC5A5 paralogs are expressed in tissues necessary for the development of reproductive organs, and therefore are plausible candidates to mediate the effects of perchlorate on sexual development, we first investigated the evolutionary history of Slc5a paralogs to better understand potential functional trajectories of the gene family. We identified two clades of slc5a paralogs with respect to an outgroup of sodium/choline cotransporters (slc5a7); these clades are the NIS clade of sodium/iodide and lactate cotransporters (slc5a5, slc5a6, slc5a8, slc5a8, and slc5a12) and the SGLT clade of sodium/glucose cotransporters (slc5a1, slc5a2, slc5a3, slc5a4, slc5a10, and slc5a11). We also characterized expression patterns of slc5a genes during development. Stickleback embryos and early larvae expressed NIS clade genes in connective tissue, cartilage, teeth, and thyroid. Stickleback males and females expressed slc5a5 and its paralogs in gonads. Single‐cell transcriptomics (scRNA‐seq) on zebrafish sex‐genotyped gonads revealed that NIS clade‐expressing cells included germ cells (slc5a5, slc5a6a, and slc5a6b) and gonadal soma cells (slc5a8l). These results are consistent with the hypothesis that perchlorate exerts its effects on sexual development by interacting with slc5a5 or its paralogs in reproductive tissues. These findings show novel expression domains of slc5 genes in stickleback and zebrafish, which suggest similar functions across vertebrates including humans, and provide candidates to mediate the effects of perchlorate on sexual development.

Delayed early life effects in the threespine stickleback.

Early life conditions can have a decisive influence on viability later in life. However, the influence of embryo density within a nest or body cavity on subsequent viability has received little attention within an ecological setting. This is surprising given that embryos often compete for limited resources, such as nutrients and oxygen, and this could influence their viability later in life through carry-over and compensatory effects. We show that the density of fertilized eggs within the nests of threespine stickleback males (Gasterosteus aculeatus) influences their viability after hatching. Embryos from larger broods hatch earlier and at a smaller size than those from smaller broods, which reduces their survival until the age of four weeks. This indicates a trade-off between the number and viability of offspring that males can raise to the hatching stage, which could explain the high incidence of partial egg cannibalism in nest-brooding fishes-as a strategy to improve the survival of remaining offspring. These results highlight the importance of considering conditions at the embryonic stage when evaluating the impact of early life conditions on viability and the adaptive value of reproductive decisions.

Copper exposure improves the upper thermal tolerance in a sex-specific manner, irrespective of fish thermal history.

Ectotherms can respond to climate change via evolutionary adaptation, usually resulting in an increase of their upper thermal tolerance. But whether such adaptation influences the phenotypic plasticity of thermal tolerance when encountering further environmental stressors is not clear yet. This is crucial to understand because organisms experience multiple stressors, besides warming climate, in their natural environment and pollution is one of those. Here, we studied the phenotypic plasticity of thermal tolerance in three-spined stickleback populations inhabiting spatially replicated thermally polluted and pristine areas before and after exposing them to a sublethal concentration of copper for one week. We found that the upper thermal tolerance and its phenotypic plasticity after copper exposure did not depend on the thermal history of fish, suggesting that five decades of thermal pollution did not result in evolutionary adaptation to thermal tolerance. The upper thermal tolerance of fish was, on the other hand, increased by ∼ 1.5°C after 1-week copper exposure in a sex-specific manner, with males having higher plasticity. To our knowledge this is the first study that shows an improvement of the upper thermal tolerance as a result of metal exposure. The results suggest that three-spined sticklebacks are having high plasticity and they are capable of surviving in a multiple-stressor scenario in the wild and that male sticklebacks seem more resilient to fluctuating environmental conditions than female.

Gene expression in male and female stickleback from populations with convergent and divergent throat coloration.

Understanding of genetic mechanisms underlying variation in sexual dichromatism remains limited, especially for carotenoid‐based colors. We addressed this knowledge gap in a gene expression study with threespine stickleback. We compared male and female throat tissues across five populations, including two in which female red coloration has evolved convergently. We found that the expression of individual genes, gene ontologies, and coexpression networks associated with red female color within a population differed between California and British Columbia populations, suggesting differences in underlying mechanisms. Comparing females from each of these populations to females from populations dominated by dull females, we again found extensive expression differences. For each population, genes and networks associated with female red color showed the same patterns for males only inconsistently. The functional roles of genes showing correlated expression with female color are unclear within populations, whereas genes highlighted through inter‐population comparisons include some previously suggested to function in carotenoid pathways. Among these, the most consistent patterns involved TTC39B (Tetratricopeptide Repeat Domain 39B), which is within a known red coloration QTL in stickleback and implicated in red coloration in other taxa.

Relationships between male secondary sexual traits, physiological state and offspring viability in the three-spined stickleback

BackgroundSexual signals produced by males play a central role in sexual selection, but the relationship between these traits and the quality of the bearer are often ambiguous. Secondary sexual traits may represent genetic quality of the bearer, resulting in positive relationships with physiological state, or may be costly to produce, showing trade-off with physiological state. A number of studies have explored the relationships between secondary sexual traits and other functional traits, but few have studied their fitness consequences. We studied the link between diverse physiological traits and both morphological and behavioural sexual traits and examined how their interplay influences offspring viability in the three-spined stickleback.ResultsMale sticklebacks showing nest building and courtship behaviour were smaller than those not investing in reproductive activities. There was no evidence that the expression of red nuptial colouration and the quality of courtship behaviour of males are positively related to their metabolic rates, swim ability, oxidative damage and mtDNA copy number. However, individuals showing larger red nuptial colour areas had higher levels of oxidative DNA damage in their sperm. Male courtship behaviour and aggressiveness, but not red colour area, were good predictors of offspring hatching and survival.ConclusionsOur results suggest that, in our study population at the southern edge of the species’ distribution, sexual colouration of male sticklebacks was not a good indicator of their body state, but both courtship quality and aggressiveness during the courtship are reliable cues of their gamete quality, influencing the viability of their offspring. Thus, females that choose mates based on their courtship behaviour will have high fitness. In the study population, which represents a fast pace-of-life with high reproductive rate and short lifespan, sexual ornaments of males may not honestly signal their physiological and physical state because they invest at maximum in a single reproductive season despite high costs.

Male reproductive adjustments to an introduced nest predator

AbstractNest predation has a large impact on reproductive success in many taxa. Defending offspring from would-be predators can also be energetically and physiologically costly for parents. Thus, to maximize their reproductive payoffs, individuals should adjust their reproductive behaviors in relation to the presence of nest predators. However, effects of nest predator presence on parental behaviors across multiple reproductive contexts remain poorly understood, particularly in non-avian taxa. We ran a series of experiments to test how the presence of an egg predator, the invasive rockpool shrimp, Palaemon elegans, influences male reproductive decisions and egg survival in a species of fish with exclusive paternal care, the three-spined stickleback, Gasterosteus aculeatus. We found that, in the presence of shrimp, male sticklebacks were less likely to build a nest, invested less in territory defense against an intruder, and tended to fan eggs in their nest less and in shorter bouts, but did not alter their investment in courtship behavior. The predator’s presence also did not affect egg survival rates, suggesting that males effectively defended their brood from the shrimp. These results show that reproducing individuals can be highly responsive to the presence of nest predators and adjust their behavioral decisions accordingly across a suite of reproductive contexts.

Carotenoids-based reddish pelvic spines in nonreproducing female and male sticklebacks (Gasterosteus aculeatus) - Signalling social dominance?

Conspicuous ornaments are often considered a result of evolution by sexual selection. According to the social selection hypothesis, such conspicuous traits may also evolve as badges of status associated with increased boldness or aggression toward conspecifics in conflicts about ecological resources. This study tested predictions from the social selection hypothesis to explain evolution of conspicuous red color of the pelvic spines of the three‐spine stickleback (Gasterosteus aculeatus). Wild nonreproducing sticklebacks were presented to pairs of dummies which differed at their pelvic spines, having either (i) normal‐sized gray or red pelvic spines or (ii) normal‐sized gray or large red pelvic spines. The experimental tank was illuminated by white or green light, since green light impedes the sticklebacks’ ability to detect red color. The dummies moved slowly around in circles at each end of the experimental tank. We quantified the parameters (i) which of the two dummies was visited first, (ii) time taken before the first visit to a dummy, (iii) distribution of the focal sticklebacks in the two zones close to each of the two dummies and in the neutral zone of the tank, (iv) close to which of the two dummies did the focal fish eat its first food‐piece, and (v) time spent until the first piece of food was eaten. This was carried out for 22 females and 29 males sticklebacks. The results suggested no effect of the color or size of the dummies’ pelvic spines, on none of the five behavioral parameters. Moreover, neither the color of the pelvic spines of the focal sticklebacks themselves (as opposed to redness of the dummies’ spines) nor their body length was associated with behavior toward the dummies. Thus, this study did not support predictions from the social selection hypothesis to explain evolution of red pelvic spines in sticklebacks.

Divergent Response to the SSRI Citalopram in Male and Female Three-Spine Sticklebacks (Gasterosteus aculeatus)

Selective serotonin reuptake inhibitors (SSRIs) are psychotropic pharmaceuticals used as antidepressants. SSRIs are commonly found in surface waters in populated areas across the globe. They exert their effect by blocking the serotonin re-uptake transporter in the presynaptic nerve ending. The present study examined whether behavioural effects to exposure to SSRI citalopram depend on personality and sex in the stickleback (Gasterosteus aculeatus). Three aspects of stickleback behaviour are examined: feeding behaviour, aggression, and boldness. We exposed sticklebacks to 350–380 ng/l citalopram for 3 weeks. Feeding and aggressive behaviour were recorded before and after exposure, whereas scototaxis behaviour was tested after exposure. The results show treatment effects in feeding and aggressive behaviour. Feeding is suppressed only in the male group (χ2 = 20.4, P < 0.001) but not in the females (χ2 = 0.91, P = 0.339). Aggressive behaviour was significantly affected by treatment (χ2 = 161.9, P < 0.001), sex (χ2 = 86.3, P < 0.001), and baseline value (χ2 = 58.8, P < 0.001). Aggressiveness was suppressed by citalopram treatment. In addition, the fish showed no change in aggression and feeding behaviour over time regardless of sex and treatment, which indicate personality traits. Only females are affected by treatment in the scototaxis test. The exposed females spent significantly (χ2 = 5.02, P = 0.050) less time in the white zone than the female controls.

Habitat deterioration relaxes resource competition and sexual selection in the threespine stickleback

The operation of sexual selection depends on ecological conditions. Thus, changes in environmental conditions because of human activities can alter the strength and direction of sexual selection, with implications for evolutionary trajectories and the viability of populations. We show that aquatic algal blooms can relax the operation of sexual selection by influencing which males are available to attract females. This is by influencing the ability of males to maintain a resource needed in mate attraction. When we exposed two competing threespine stickleback males Gasterosteus aculeatus, whose attractiveness to females was known, to either clear or algal‐turbid water, nest abandonment was more common in clear water, and it was usually the unattractive male that abandoned his nest. In turbid water, on the other hand, nest abandonments were less common and when they occurred, the probability increased that the attractive male abandoned his nest, and that the unattractive male subsequently occupied it. This change in the composition of nesting males increased the mating success of unattractive males. Thus, our results reveal a new mechanism through which habitat deterioration can influence sexual selection, by altering success in the competition for a resource critical in mate attraction, a territory with a nest in this case. This could be a common mechanism, considering the prevalence of resource competition in mate choice systems. On a broader level, our results emphasise the importance of considering the impact of environmental changes on the outcome of resource competition when investigating the influence that environmental disturbances have on the operation of sexual selection and thereby on evolutionary processes and population dynamics.

Dynamics of Prolactin Axis Genes in the Brain of Male and Female Three-spined Stickleback Gasterosteus aculeatus (Gasterostaidae) during Short-Term Freshwater Adaptation

Expression of prolactin axis genes (prolactin Prl1, prolactin-like hormone Prl2, prolactin receptor “a” PrlRa, and prolactin receptor “b” PrlRb) have been studied in the brains of females and males of the three-spined stickleback Gasterosteus aculeatus upon adaptation to fresh water. The expression of the Prl1 gene in females was significantly higher after 24-h adaptation to the freshwater relative to the control group (seawater) and to that in males at the same time point. No changes in Prl2 gene expression in females and Prl1 in males were detected. In males, after 12 and 18 h of adaptation to fresh water, higher expression of the Prl2 gene was observed relative to the control group. The expression of the PrlRa gene in males in seawater is higher than that in females; upon adaptation to fresh water, it does not change in females, and it decreases in males gradually after 3 h of being transferred to fresh water. No differences in the expression of the PrlRb gene between females and males in seawater were detected; however, after 24 h of freshwater adaptation, this parameter was higher in females than in males. Changes in the expression of prolactin axis elements during freshwater adaptation are gender-dependent, and the contribution of prolactin and prolactin-like hormone to adaptation of females and males of the three-spined stickleback to fresh water is significantly different.

Phenotypic divergence among threespine stickleback that differ in nuptial coloration.

By studying systems in their earliest stages of differentiation, we can learn about the evolutionary forces acting within and among populations and how those forces could contribute to reproductive isolation. Such an understanding would help us to better discern and predict how selection leads to the maintenance of multiple morphs within a species, rather than speciation. The postglacial adaptive radiation of the threespine stickleback (Gasterosteus aculeatus) is one of the best‐studied cases of evolutionary diversification and rapid, repeated speciation. Following deglaciation, marine stickleback have continually invaded freshwater habitats across the northern hemisphere and established resident populations that diverged innumerable times from their oceanic ancestors. Independent freshwater colonization events have yielded broadly parallel patterns of morphological differences in freshwater and marine stickleback. However, there is also much phenotypic diversity within and among freshwater populations. We studied a lesser‐known freshwater “species pair” found in southwest Washington, where male stickleback in numerous locations have lost the ancestral red sexual signal and instead develop black nuptial coloration. We measured phenotypic variation in a suite of traits across sites where red and black stickleback do not overlap in distribution and at one site where they historically co‐occurred. We found substantial phenotypic divergence between red and black morphs in noncolor traits including shape and lateral plating, and additionally find evidence that supports the hypothesis of sensory drive as the mechanism responsible for the evolutionary switch in color from red to black. A newly described third “mixed” morph in Connor Creek, Washington, differs in head shape and size from the red and black morphs, and we suggest that their characteristics are most consistent with hybridization between anadromous and freshwater stickleback. These results lay the foundation for future investigation of the underlying genetic basis of this phenotypic divergence as well as the evolutionary processes that may drive, maintain, or limit divergence among morphs.

Collective action reduces androgen responsiveness with implications for shoaling dynamics in stickleback fish

Androgens, traditionally viewed as hormones that regulate secondary sexual characteristics and reproduction in male vertebrates, are often modulated by social stimuli. High levels of the ‘social hormone’ testosterone (T) are linked to aggression, dominance, and competition. Low T levels, in contrast, promote sociopositive behaviours such as affiliation, social tolerance, and cooperation, which can be crucial for group-level, collective behaviours. Here, we test the hypothesis that - in a collective context - low T levels should be favourable, using non-reproductive male and female stickleback fish (Gasterosteus aculeatus) and non-invasive waterborne hormone analysis. In line with our predictions, we show that the fishes' T levels were significantly lower during shoaling compared to when alone, with high-T individuals showing the largest decrease. Ruling out stress-induced T suppression and increased T conversion into oestradiol, we find evidence that shoaling directly affects androgen responsiveness. We also show that groups characterized by lower mean T exhibit less hierarchical leader-follower dynamics, suggesting that low T promotes egalitarianism. Overall, we show that collective action results in lower T levels, which may serve to promote coordination and group performance. Our study, together with recent complementary findings in humans, emphasizes the importance of low T for the expression of sociopositive behaviour across vertebrates, suggesting similarities in endocrine mechanisms.

Attractive male sticklebacks carry more oxidative DNA damage in the soma and germline.

Trade-offs between the expression of sexual signals and the maintenance of somatic and germline tissues are expected when these depend upon the same resources. Despite the importance of sperm DNA integrity, its trade-off with sexual signalling has rarely been explored. We experimentally tested the trade-off between carotenoid-based sexual coloration and oxidative DNA damage in skeletal muscle, testis and sperm by manipulating reproductive schedule (early vs. late onset of breeding) in male three-spined sticklebacks. Oxidative DNA damage was measured as the amount of 8-hydroxy-2-deoxyguanosine in genomic DNA. Irrespective of the experimentally manipulated reproductive schedule, individuals investing more in red coloration showed higher levels of oxidative DNA damage in muscle, testis and sperm during the peak breeding season. Our results show that the expression of red coloration traded off against the level of oxidative DNA damage possibly due to the competing functions of carotenoids as colorants and antioxidants. Thus, female sticklebacks may risk fertility and viability of offspring by choosing redder, more deteriorated partners with decreased sperm DNA integrity. The evolution of sexual signal may be constrained by oxidative DNA damage in the soma and germline.

Neurogenomic insights into paternal care and its relation to territorial aggression

Motherhood is characterized by dramatic changes in brain and behavior, but less is known about fatherhood. Here we report that male sticklebacks—a small fish in which fathers provide care—experience dramatic changes in neurogenomic state as they become fathers. Some genes are unique to different stages of paternal care, some genes are shared across stages, and some genes are added to the previously acquired neurogenomic state. Comparative genomic analysis suggests that some of these neurogenomic dynamics resemble changes associated with pregnancy and reproduction in mammalian mothers. Moreover, gene regulatory analysis identifies transcription factors that are regulated in opposite directions in response to a territorial challenge versus during paternal care. Altogether these results show that some of the molecular mechanisms of parental care might be deeply conserved and might not be sex-specific, and suggest that tradeoffs between opposing social behaviors are managed at the gene regulatory level.

Correction to ‘Parenting behaviour is highly heritable in male stickleback’

[This corrects the article DOI: 10.1098/rsos.171029.].