Parallelism and divergence in immune responses: a comparison of expression levels in two lakes

Question: How do immune phenotypes differ between infected and uninfected wild individuals, and is the effect the same in different populations? Organisms: Threespine stickleback (Gasterosteus aculeatus) from two lake populations on the island of North Uist, Scotland, sampled in May 2015. Methods: For each fish, we recorded length, sex, reproductive status, condition, and parasitic infection. We measured the expression levels of eight genes that act as key markers of immune system function using qPCR, and then examined the relationship between measured factors and immune gene expression profiles within each population. Conclusions: Populations differed significantly in their immune gene expression profiles. Within each population, multiple factors, including condition, reproductive status, and Schistocephalus solidus infection levels, were found to correlate with expression levels of different arms of the immune system

A long-term copper exposure on freshwater ecosystem using lotic mesocosms: Individual and population responses of three-spined sticklebacks (Gasterosteus aculeatus)

Three-spined stickleback (Gasterosteus aculeatus) was used as the highest trophic level predator in an outdoor mesocosm study assessing the effect of environmentally realistic copper concentration (0, 5, 25 and 75 μg L−1) over 18 months of continuous exposure. Condition factor, organosomatic indices (HIS, GSI and SSI) as well as copper bioaccumulation in the liver were measured at 15 days, 2, 4, 6, 10, 14 and 18 months after the beginning of the contamination. Population monitoring was realised after 6 and 18 months of contamination, allowing two reproduction periods to be measured. Results showed that condition factor was affected at medium and high copper concentrations and HSI was sporadically affected in all copper exposure, depending on the sex of the fish. GSI did not show any significant differences and SSI was lowered in the medium and high copper levels. Bioaccumulation was significantly different in males and females and fluctuated with season. A negative correlation was observed between copper bioaccumulation in the liver and fish size and a positive correlation with nominal copper concentration in the water was found. There was a negative correlation between condition factor, organosomatic indices and bioaccumulation in the liver. Population monitoring showed a significantly higher fish mean length after 6 months and a higher abundance after 18 months of exposure at the highest copper level. We conclude that indirect effects such as food and habitat availability or lower predation pressure on eggs and juveniles might have led to higher stickleback population abundances at the highest copper level. This highlights the need to study all the trophic levels when monitoring ecosystem health. Considering the population and the individual responses after 18 months of copper exposure, the NOEC for three-spined sticklebacks was 25 μg L−1 (or 20 μg L−1 if we consider the average effective concentration), with a LOEC of 75 μg L−1 (or 57 μg L−1, AEC)

Parallelism and divergence in immune responses: a comparison of expression levels in two lakes

Question: How do immune phenotypes differ between infected and uninfected wild individuals, and is the effect the same in different populations? Organisms: Threespine stickleback (Gasterosteus aculeatus) from two lake populations on the island of North Uist, Scotland, sampled in May 2015. Methods: For each fish, we recorded length, sex, reproductive status, condition, and parasitic infection. We measured the expression levels of eight genes that act as key markers of immune system function using qPCR, and then examined the relationship between measured factors and immune gene expression profiles within each population. Conclusions: Populations differed significantly in their immune gene expression profiles. Within each population, multiple factors, including condition, reproductive status, and Schistocephalus solidus infection levels, were found to correlate with expression levels of different arms of the immune system

Extensive Copy-Number Variation of Young Genes across Stickleback Populations

MM received funding from the Max Planck innovation funds for this project. PGDF was supported by a Marie Curie European Reintegration Grant (proposal nr 270891). CE was supported by German Science Foundation grants (DFG, EI 841/4-1 and EI 841/6-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Genomic divergence between nine- and three-spined sticklebacks

Background: Comparative genomics approaches help to shed light on evolutionary processes that shape differentiation between lineages. The nine-spined stickleback (Pungitius pungitius) is a closely related species of the ecological ‘supermodel’ three-spined stickleback (Gasterosteus aculeatus). It is an emerging model system for evolutionary biology research but has garnered less attention and lacks extensive genomic resources. To expand on these resources and aid the study of sticklebacks in a phylogenetic framework, we characterized nine-spined stickleback transcriptomes from brain and liver using deep sequencing. Results: We obtained nearly eight thousand assembled transcripts, of which 3,091 were assigned as putative oneto- one orthologs to genes found in the three-spined stickleback. These sequences were used for evaluating overall differentiation and substitution rates between nine- and three-spined sticklebacks, and to identify genes that are putatively evolving under positive selection. The synonymous substitution rate was estimated to be 7.1 × 10-9 per site per year between the two species, and a total of 165 genes showed patterns of adaptive evolution in one or both species. A few nine-spined stickleback contigs lacked an obvious ortholog in three-spined sticklebacks but were found to match genes in other fish species, suggesting several gene losses within 13 million years since the divergence of the two stickleback species. We identified 47 SNPs in 25 different genes that differentiate pond and marine ecotypes. We also identified 468 microsatellites that could be further developed as genetic markers in nine-spined sticklebacks. Conclusion: With deep sequencing of nine-spined stickleback cDNA libraries, our study provides a significant increase in the number of gene sequences and microsatellite markers for this species, and identifies a number of genes showing patterns of adaptive evolution between nine- and three-spined sticklebacks. We also report several candidate genes that might be involved in differential adaptation between marine and freshwater nine-spined sticklebacks. This study provides a valuable resource for future studies aiming to identify candidate genes underlying ecological adaptation in this and other stickleback species

Endocrine disrupting effects on the nesting behaviour of male three-spined stickleback Gasterosteus aculeatus L

The analysis of patterns of temporal variability in the nesting behaviour of male threespined stickleback (Gasterosteus aculeatus) exposed to the synthetic oestrogen, 17β-ethinylestradiol, revealed immediate, but transient, treatment-related effects. Gluing frequency and time spent near nest were significantly reduced in exposed fish at the beginning of the experiment. The expression of these behaviours subsequently recovered and there was no effect of treatment on nest building success. The potential causes and implications of these findings are discussed

Evidence suggesting that di-n-butyl phthalate has anti-androgenic effects in fish

This article is the pre-print version of the full and final published article.Phthalate ester plasticizers are anti-androgenic in mammals. High doses of certain phthalates consistently interfere with the normal development of male offspring exposed in utero, causing disrupted sperm production, abnormal development of the genitalia, and in some cases infertility. In the environment, phthalates are considered ubiquitous and are commonly measured in aquatic ecosystems at low ng to mu g per litre concentrations. Given the similarity between mammalian and teleost endocrine systems, phthalate esters may be able to cause anti-androgenic endocrine disruption in fish in the wild. In the present study, adult male three-spined sticklebacks (Gasterosteus aculetaus) (n = 8) were exposed to di-n-butyl phthalate (DBP) (0, 15, and 35 mu g DBP/L) for 22 d and analyzed for changes in nesting behavior, plasma androgen concentrations, spiggin concentrations, and steroidogenic gene expression. Plasma testosterone concentrations were significantly higher in males from the 35 mu g DBP/L group compared with the solvent control, whereas plasma 11-ketotestosterone concentrations were not significantly affected. Expression of steroid acute regulatory protein and 3 beta-hydroxysteroid dehydrogenase remained unchanged. Spiggin concentrations were significantly lower in the males exposed to 35 mu g DBP/L. Nest building appeared to be slower in some males exposed to DBP, but this was not statistically significant. These results suggest that DBP has anti-androgenic effects in fish. However, further research is required to firmly establish the consequences of chronic DBP exposure in fish

Opsin expression predicts male nuptial color in threespine stickleback.

Theoretical models of sexual selection suggest that male courtship signals can evolve through the build-up of genetic correlations between the male signal and female preference. When preference is mediated via increased sensitivity of the signal characteristics, correlations between male signal and perception/sensitivity are expected. When signal expression is limited to males, we would expect to find signal-sensitivity correlations in males. Here, we document such a correlation within a breeding population of threespine stickleback mediated by differences in opsin expression. Males with redder nuptial coloration express more long-wavelength-sensitive (LWS) opsin, making them more sensitive to orange and red. This correlation is not an artifact of shared tuning to the optical microhabitat. Such correlations are an essential feature of many models of sexual selection, and our results highlight the potential importance of opsin expression variation as a substrate for signal-preference evolution. Finally, these results suggest a potential sensory mechanism that could drive negative frequency-dependent selection via male-male competition and thus maintain variation in male nuptial color

Rapid bioconcentration of steroids in the plasma of three-spined stickleback Gasterosteus aculeatus exposed to waterborne testosterone and 17β-oestradiol

The relationship over time between the concentrations of two steroids, singly and in combination, in a static exposure system and in the blood of three-spined stickleback Gasterosteus aculeatus, held within the exposure system was investigated. Groups of three-spined stickleback were exposed (nominally) to either 1000 ng l1 17β-oestradiol (E2), testosterone (T) or E2 and T in combination at the same concentrations for 6 days. Both water and fish were sampled at intervals and steroid concentrations in both compartments were determined. The plasma steroid time profile revealed a rapid bioconcentration within the first 6 h of exposure. The plasma steroid levels attained at this time point (20–90 ng ml1) were up to 50-fold (E2) and 200-fold (T) greater than the actual levels of steroid measured in the exposure water, while levels in the blood of control fish did not exceed 4 ng ml1. The substantial elevation of plasma steroid levels relative to the concentrations of steroid to which the fish were exposed in the ambient water gives scope for delivery of the steroids to target endocrine tissues at levels far in excess of what might be predicted on the basis of passive branchial uptake alone. These results are discussed in relation to endocrine disruption, and in particular the occurrence of effects in fish exposed to levels of endocrine active substances that are seemingly physiologically irrelevant