Pungitius Pungitius Research Articles

Chromosomal Fusions Facilitate Adaptation to Divergent Environments in Threespine Stickleback.

Chromosomal fusions are hypothesized to facilitate adaptation to divergent environments, both by bringing together previously unlinked adaptive alleles and by creating regions of low recombination that facilitate the linkage of adaptive alleles; but, there is little empirical evidence to support this hypothesis. Here, we address this knowledge gap by studying threespine stickleback (Gasterosteus aculeatus), in which ancestral marine fish have repeatedly adapted to freshwater across the northern hemisphere. By comparing the threespine and ninespine stickleback (Pungitius pungitius) genomes to a de novo assembly of the fourspine stickleback (Apeltes quadracus) and an outgroup species, we find two chromosomal fusion events involving the same chromosomes have occurred independently in the threespine and ninespine stickleback lineages. On the fused chromosomes in threespine stickleback, we find an enrichment of quantitative trait loci underlying traits that contribute to marine versus freshwater adaptation. By comparing whole-genome sequences of freshwater and marine threespine stickleback populations, we also find an enrichment of regions under divergent selection on these two fused chromosomes. There is elevated genetic diversity within regions under selection in the freshwater population, consistent with a simulation study showing that gene flow can increase diversity in genomic regions associated with local adaptation and our demographic models showing gene flow between the marine and freshwater populations. Integrating our results with previous studies, we propose that these fusions created regions of low recombination that enabled the formation of adaptative clusters, thereby facilitating freshwater adaptation in the face of recurrent gene flow between marine and freshwater threespine sticklebacks.

Reproductive characteristics, egg and larval development of short ninespine stickleback, Pungitius kaibarae

In this study, the reproductive behavior and embryonic and larval development of the short ninespine stickleback Pungitius kaibarae was described and illustrated based on observations during spawning, hatching, and larval rearing trials. Adult P. kaibarae were collected downstream in Jinhae during the reproductive season (April-May). Males had nuptial coloration on their entire black bodies, with blue dorsal spines and yellow eyes, whereas females had a brown spotted pattern on their bodies. Males built nests on the stems of water weeds and attracted females. Fertilization occurred in the nest immediately after spawning, and males guarded the eggs until hatching. The fertilized eggs of P. kaibarae were spherical, demersal, adhesive, and transparent, and each egg measured 1.43 ± 0.07 mm in diameter. The morula, blastula, and gastrula stages, as well as hatching began at 5, 18.5, 21.5, and 96 post fertilization (HPF) , respectively, at 20.0 ± 0.5°C. The newly hatched larvae had a total length (TL) of 5.67 ± 0.50 mm, with a yolk volume of 0.583 ± 0.059 mm3. Their mouths and anuses had not yet opened. At 2 days posthatching (days post hatching, DPH), the yolk was completely absorbed and the larvae began to feed exogenously. Pigmentation was observed in freshly hatched larvae 4 h after hatching, with the presence of eight areas with a dotted pattern on the dorsal surface of the larvae and dispersed spots on the head and yolk sac. At 30 DPH, the TL of the juveniles was 21.34 ± 1.70 mm. The nest area and number of eggs were 259.56 ± 101.39 mm2 (75.18-506.04) and 155.33 ± 114.12 (0-437), respectively.

Swimming behaviour in two ecologically similar three-spined (Gasterosteus aculeatus L.) and nine-spined sticklebacks (Pungitius pungitius L.): a comparative approach for modelling the toxicity of metal mixtures.

Sticklebacks (Gasterosteiformes) are increasingly used in ecological and evolutionary research and have become well established as role model species for biologists. However, ecotoxicology studies concerning behavioural effects in sticklebacks regarding stress responses, mainly induced by chemical mixtures, have hardly been addressed. For this purpose, we investigated the swimming behaviour (including mortality rate based on 96-h LC50 values) of two ecologically similar three-spined (Gasterosteus aculeatus) and nine-spined sticklebacks (Pungitius pungitius) to short-term (up to 24 h) metal mixture (MIX) exposure. We evaluated the relevance and efficacy of behavioural responses of test species in the early toxicity assessment of chemical mixtures. Fish exposed to six (Zn, Pb, Cd, Cu, Ni, and Cr) metals in the mixture were either singled out by the Water Framework Directive as priority or as relevant substances in surface water, which was prepared according to the environmental quality standards (EQSs) of these metals set for inland waters in the European Union (EU) (Directive 2013/39/EU). The performed behavioural analysis showed the main effect on the interaction between time, species, and treatment variables. Although both species exposed to MIX revealed a decreasing tendency in swimming activity, these species' responsiveness to MIX was somewhat different. Substantial changes in the activity of G. aculeatus were established after a 3-h exposure to MIX solutions, which was 1.43-fold lower, while in the case of P. pungitius, 1.96-fold higher than established 96-h LC50 values for each species. This study demonstrated species-specific differences in response sensitivity to metal-based water pollution, indicating behavioural insensitivity of P. pungitius as model species for aquatic biomonitoring and environmental risk assessments.

A new species of nine-spined stickleback, Pungitius modestus (Gasterosteiformes, Gasterosteidae), from northern Honshu, Japan

A new species of nine-spined stickleback, Pungitius modestus, is described based on the holotype and 17 paratypes (38.751.7 mm standard length) collected from the inland area of Yamagata Prefecture, northern Honshu, Japan. The new species is distinguished from the other species of Pungitius by the following combination of characters: 3032 small unconnected lateral plates; dorsal-fin rays VIIIX (usually IX)+911; anal-fin rays 710 (usually 8); pectoral-fin rays 10; a short spiny dorsal fin base (26.5%29.8% SL); the first spiny dorsal fin spine behind the pectoral-fin base; a long pre-anal fin (59.9%67.4% SL); the anal-fin spine below the 1st3rd dorsal-fin rays; a short pelvic-fin spine (6.3%9.1% SL); a short anal-fin spine (4.1%6.0% SL); a long caudal peduncle (14.3%19.7% SL); no body markings; membranes of the dorsal-fin spines dark brown with black pigments; the entire male body, and soft dorsal and anal fins, becoming black in the breeding season; the anteroventral process of the ectocoracoid present; and the dorsal extension of the ascending process of the pelvis level with the dorsal-most actinost.

Characterization of the abiotic drivers of abundance of nearshore Arctic fishes.

Fish are critical ecologically and socioeconomically for subsistence economies in the Arctic, an ecosystem undergoing unprecedented environmental change. Our understanding of the responses of nearshore Arctic fishes to environmental change is inadequate because of limited research on the physicochemical drivers of abundance occurring at a fine scale. Here, high‐frequency in situ measurements of pH, temperature, salinity, and dissolved oxygen were paired with daily fish catches in nearshore Alaskan waters of the Beaufort Sea. Due to the threat that climate change poses to high‐latitude marine ecosystems, our main objective was to characterize the abiotic drivers of abundance and elucidate how nearshore fish communities may change in the future. We used generalized additive models (GAMs) to describe responses to the nearshore environment for 18 fish species. Relationships between abundance and the physicochemical environment were variable between species and reflected life history. Each abiotic covariate was significant in at least one GAM, exhibiting both nonlinear and linear associations with abundance. Temperature was the most important predictor of abundance and was significant in GAMs for 11 species. Notably, pH was a significant predictor of abundance for six species: Arctic cod (Boreogadus saida), broad whitefish (Coregonus nasus), Dolly Varden (Salvelinus malma), ninespine stickleback (Pungitius pungitius), saffron cod (Eleginus gracilis), and whitespotted greenling (Hexagrammos stelleri). Broad whitefish and whitespotted greenling abundance was positively associated with pH, while Arctic cod and saffron cod abundance was negatively associated with pH. These results may be a bellwether for future nearshore Arctic fish community change by providing a foundational characterization of the relationships between abundance and the abiotic environment, particularly in regard to pH, and demonstrate the importance of including a wider range of physicochemical habitat covariates in future research.

Інвазійні види риб у іхтіоценозах водойм Західного Полісся України

Purpose. To study ichthyocenoses, species composition and the current state of fish populations in water bodies of the Western Polissya of Ukraine by focusing on their changes under the effect of invasive fish species. Methodology. Ichthyological studies were carried out in natural and artificial water bodies for various purposes in the Western Polissya of Ukraine during 2007-2017. In particular, fish surveys were carried out using beach seins and gill nets with different mesh sizes in the karst lakes Svityaz and Pischane from the Shatskiy National Nature Park, channel lakes Lyubyaz and Nobel from the Pripyat River basin, right-bank tributaries of the Pripyat Rivers including Styr and Goryn Rivers, Khrinnitske reservoir from the Styr River basin, fish ponds of Bochanitsa village and Progress LLC (Goryn River basin). The material for the study were both the populations of native and invasive fish species. Findings. The results of our own studies and data of other authors highlighted the issue of the spread of invasive fish species in water bodies of the river-lake network of Western Polissya of Ukraine, presented the diagrams of the distribution of these fish in different water bodies of different origins of the above-mentioned region. Originality. The greatest threat to the abundance of aboriginal fish species in this region was found to be self-reproducing populations of the brown bullhead (Ictalurus nebulosus), Amur sleeper (Percсottus glenіi), stone moroko or topmouth gudgeon (Pseudorasbora parva), three-spined (Gasterosteus aculeatus) and nine-spined (Punguitius punguitius) sticklebacks. In particular, the composition of their gut content during the spawning period included 95% of eggs of fish species, which spawned in spring, as shown in the diagrams presented in this paper. Practical Value. The proposed measures to be carried out at the national and regional levels will help prevent the ingress of new invasions and mitigate the impact of the existing ones on the ichthyocenoses of the reservoirs of Western Polissya of Ukraine. Key words: ichthyocenoses, invasive fish species, aboriginal ichthyofauna, Western Polissya.

Species-environment relationships of fish and map-based variables in small boreal streams: Linkages with climate change and bioassessment.

Species–environment relationships were studied between the occurrence of 13 fish and lamprey species and 9 mainly map‐based environmental variables of Finnish boreal small streams. A self‐organizing map (SOM) analysis showed strong relationships between the fish species and environmental variables in a single model (explained variance 55.9%). Besides basic environmental variables such as altitude, catchment size, and mean temperature, land cover variables were also explored. A logistic regression analysis indicated that the occurrence probability of brown trout, Salmo trutta L., decreased with an increasing percentage of peatland ditch drainage in the upper catchment. Ninespine stickleback, Pungitius pungitius (L.), and three‐spined stickleback, Gasterosteus aculeatus L., seemed to benefit from urban areas in the upper catchment. Discovered relationships between fish species occurrence and land‐use attributes are encouraging for the development of fish‐based bioassessment for small streams. The presented ordination of the fish species in the mean temperature gradient will help in predicting fish community responses to climate change.

Automated improvement of stickleback reference genome assemblies with Lep-Anchor software.

We describe an integrative approach to improve contiguity and haploidy of a reference genome assembly and demonstrate its impact with practical examples. With two novel features of Lep-Anchor software and a combination of dense linkage maps, overlap detection and bridging long reads, we generated an improved assembly of the nine-spined stickleback (Pungitius pungitius) reference genome. We were able to remove a significant number of haplotypic contigs, detect more genetic variation and improve the contiguity of the genome, especially that of X chromosome. However, improved scaffolding cannot correct for mosaicism of erroneously assembled contigs, demonstrated by a de novo assembly of a 1.6-Mbp inversion. Qualitatively similar gains were obtained with the genome of three-spined stickleback (Gasterosteus aculeatus). Since the utility of genome-wide sequencing data in biological research depends heavily on the quality of the reference genome, the improved and fully automated approach described here should be helpful in refining reference genome assemblies.

Multiple paths to the same destination: Influence of gene flow on convergent evolution.

Elucidation of the genetic mechanisms of convergent evolution, the evolution of similar or the same phenotypes in phylogenetically independent lineages, helps predict how populations will respond to the same selective pressures. Convergent evolution can be caused by either the fixation of identical-by-descent alleles, independent mutations at the same gene, or mutations in different genes controlling the same trait. To what extent does the fixation of identical-by-descent alleles lead to convergent evolution in isolated populations where inflow of adaptive alleles from other populations is limited? In a From the Cover article in this issue of Molecular Ecology,Kemppainenet al. (2021) compared the genetic basis for the reduction of pelvic structures in three isolated freshwater populations of nine-spined stickleback (Pungitius pungitius) from Northern Europe. The authors used quantitative trait loci (QTL) mapping to reveal that the pelvic reduction in these three populations was caused by mutations at different genetic loci. In contrast to studies in three-spined stickleback (Gasterosteus aculeatus), where independently derived Pitx1 mutations were shown to be responsible for plate reduction across multiple freshwater populations, Kemppainen et al. (2021) found Pitx1 to be the candidate causative gene for only one population of P.pungitius. This study highlights the importance of genetic studies of convergent evolution, not only in the presence of gene flow but also in its absence for a better understanding of the genetic architecture of convergent evolution.

Adaptive Divergence under Gene Flow along an Environmental Gradient in Two Coexisting Stickleback Species.

There is a general and solid theoretical framework to explain how the interplay between natural selection and gene flow affects local adaptation. Yet, to what extent coexisting closely related species evolve collectively or show distinctive evolutionary responses remains a fundamental question. To address this, we studied the population genetic structure and morphological differentiation of sympatric three-spined and nine-spined stickleback. We conducted genotyping-by-sequencing and morphological trait characterisation using 24 individuals of each species from four lowland brackish water (LBW), four lowland freshwater (LFW) and three upland freshwater (UFW) sites in Belgium and the Netherlands. This combination of sites allowed us to contrast populations from isolated but environmentally similar locations (LFW vs. UFW), isolated but environmentally heterogeneous locations (LBW vs. UFW), and well-connected but environmentally heterogenous locations (LBW vs. LFW). Overall, both species showed comparable levels of genetic diversity and neutral genetic differentiation. However, for all three spatial scales, signatures of morphological and genomic adaptive divergence were substantially stronger among populations of the three-spined stickleback than among populations of the nine-spined stickleback. Furthermore, most outlier SNPs in the two species were associated with local freshwater sites. The few outlier SNPs that were associated with the split between brackish water and freshwater populations were located on one linkage group in three-spined stickleback and two linkage groups in nine-spined stickleback. We conclude that while both species show congruent evolutionary and genomic patterns of divergent selection, both species differ in the magnitude of their response to selection regardless of the geographical and environmental context.

Genetic population structure constrains local adaptation in sticklebacks.

Repeated and independent adaptation to specific environmental conditions from standing genetic variation is common. However, if genetic variation is limited, the evolution of similar locally adapted traits may be restricted to genetically different and potentially less optimal solutions or prevented from happening altogether. Using a quantitative trait locus (QTL) mapping approach, we identified the genomic regions responsible for the repeated pelvic reduction (PR) in three crosses between nine-spined stickleback populations expressing full and reduced pelvic structures. In one cross, PR mapped to linkage group 7 (LG7) containing the gene Pitx1, known to control pelvic reduction also in the three-spined stickleback. In the two other crosses, PR was polygenic and attributed to 10 novel QTL, of which 90% were unique to specific crosses. When screening the genomes from 27 different populations for deletions in the Pitx1 regulatory element, these were only found in the population in which PR mapped to LG7, even though the morphological data indicated large-effect QTL for PR in several other populations as well. Consistent with the available theory and simulations parameterized on empirical data, we hypothesize that the observed variability in genetic architecture of PR is due to heterogeneity in the spatial distribution of standing genetic variation caused by >2× stronger population structuring among freshwater populations and >10× stronger genetic isolation by distance in the sea in nine-spined sticklebacks as compared to three-spined sticklebacks.

Genomic evidence supports the introgression between two sympatric stickleback species inhabiting the White Sea basin

Interspecies hybridization is driven by a complex interplay of factors where introgression plays an important role. In the present study, the transfer of genetic material, between two quite distant fish species from different genera, through spontaneous hybridization was documented with dedicated molecular and bioinformatics tools. We investigate the genomic landscape of putative stickleback-relative introgression by carefully analyzing the tractable transposable elements (TE) on the admixed genome of some individuals of two sympatric stickleback species inhabiting northwestern Russia, namely the three-spined (Gasterosteus aculeatus) and the nine-spined (Pungitius pungitius) sticklebacks. Our data revealed that unique TE amplification types exist, supporting our proposed hypothesis that infers on the interspecific introgression. By running a restriction site-associated DNA sequencing (RAD-Seq) with eight samples of G. aculeatus and P. pungitius and subjecting further the results to a contrasting analysis by variated bioinformatic tools, we identified the related introgression-linked markers. The admixture nature observed in a single sample of the nine-spined stickleback demonstrated the possible traces of remote introgression between these two species. Our work reveals the potential that introgression has on providing particular variants at a high-frequency speed while linking blocks of sequence with multiple functional mutations. However, even though our results are of significant interest, an increased number of samples displaying the introgression are required to further ascertain our conclusions.

Feeding of young-of-the-year fishes of the Curonian lagoon of the Baltic sea in 2016

Results of studies on nutrition of juvenile fishes of the Curonian Lagoon of the Baltic Sea are presented. Material on young-of-the-years nutrition was collected in October 2016 during the expeditions of «AtlantNIRO» at 14 standard stations in the Curonian Lagoon. A total of 418 specimens of young-of-the-years were collected and processed. Juveniles of fishes of the Curonian Lagoon were represented by 10 species: pikeperch, bream, roach, perch, smelt, ruffe, three-spined stickleback, ninespine stickleback, bleak and sabrefish. Planktonic and benthic invertebrates formed a basis of the young-of-the-years diet. In most species of juvenile fishes, the nutritional spectra did not differ from the nutritional spectra in the range. An exception was juveniles of the ruff and ninespine stickleback, in which planktonic crustaceans predominated in the diet, while in other reservoirs they consumed bottom organisms. Only Cladocera and Copepoda were found in the diet of roach of juveniles; bottom organisms were absent. In the range of roach juveniles, bottom organisms and mollusks prevailed. The food similarity indices for juvenile fish in the Curonian Lagoon are quite high, which may indicate a tension in food relations between juveniles and (or) partial or complete overlap of their food niches. The weakening of food competition is ensured by the divergence of daily dietary peaks. Three-spined and nine-spined sticklebacks as well as a sabrefish and sticklebacks have the closest food spectrum. On the contrary, sabrefish and bream have a different food spectrum. The peculiarity of feeding of pikeperch juveniles in 2016 was the lack of transition to predatory nutrition.

The Proteocephalus species-aggregate (Cestoda) in sticklebacks (Gasterosteidae) of the Nearctic Region, including description of a new species from brook stickleback, Culaea inconstans.

A survey of the species of the Proteocephalus-aggregate from sticklebacks (Actinopterygii: Gasterosteidae) is provided. The occurrence of three species in North America is confirmed: (i) Proteocephalus filicollis (Rudolphi, 1802), which has been reported from the three-spined stickleback, Gasterosteus aculeatus Linnaeus, in the northeastern part of North America (Newfoundland); (ii) Proteocephalus pugetensis Hoff et Hoff, 1929 occurs also in G. aculeatus, but in northwestern North America (British Columbia and Washington); and (iii) Proteocephalus culaeae sp. n., which is described from the brook stickleback, Culaea inconstans (Kirtland), in Manitoba (Canada). Another species, Proteocephalus ambiguus (Dujardin, 1845), a specific parasite of the nine-spined stickleback, Pungitius pungitius (Linnaeus), and type species of the genus, has also been found in North America (Alberta, Canada), but its vouchers are in poor condition and cannot be reliable assigned to this species. Both species reported from three-spined stickleback differ from each other by the shape of the scolex (rounded in P. filicollis versus continuously tapered towards the anterior extremity in P. pugetensis) and the apical sucker (widely oval to subspherical in frontal view in P. filicollis versus flattened in P. pugetensis). Proteocephalus culaeae sp. n. is characterised by a short body composed of a few, continuously widened proglottids, a short scolex narrower than the strobila and devoid of an apical sucker, a short, pyriform cirrus sac, no vaginal sphincter, and few testes. A key to species of the Proteocephalus-aggregate from sticklebacks is provided.

Metabarcoding of native and invasive species in stomach contents of Great Lakes fishes.

As aquatic invasive species (AIS) proliferate worldwide, a better understanding of their roles in invaded habitats is needed to inform management and introduction prevention strategies and priorities. Metabarcoding of stomach content DNA (scDNA) shows considerable promise in such regard. We thus metabarcoded scDNA from two non-native fish species (alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax)), and three native ones (bloater (Coregonus hoyi), ninespine stickleback (Pungitius pungitius), and slimy sculpin (Cottus cognatus)). Fishes (N = 376) were sampled in spring 2009 and 2010 from 73–128 m depths at three Lake Michigan sites. Four mitochondrial cytochrome oxidase 1 (CO1) primer sets designed to target five potential AIS prey, and a universal aquatic invertebrate CO1 primer set targeting both native and AIS prey were used. Quality controlled prey amplicons were matched to three AIS prey: Bythotrephes longimanus (mean percent frequency occurrence, all samples = 7%), Cercopagis pengoi (5%), and Dreissena rostriformis bugensis (11%). Neither invasive prey Dreissena polymorpha nor Hemimysis anomala were detected. Native prey Leptodiaptomus sicilis, Limnocalanus macrurus, and Mysis diluviana were relatively common in scDNA (respective mean percent occurrences, all samples: 48%, 25%, 42%). Analysis of variation in prey occurrences for sample site, predator species, sample year, sample depth, and predator total length (TL) indicated site and predator species were most important. However, B. longimanus occurrence in scDNA depended upon predator TL, perhaps indicative of its unique defensive spine limiting susceptibility to predation until fishes exceed species-specific gape-based limitations. Our analysis of native and invasive prey species indicated possible indirect AIS impacts such as native predators switching their diet due to AIS-driven losses of preferred native prey. Metabarcoding demonstrated that AIS are integrated components of the offshore Lake Michigan food web, with both native and non-native predators, and both invasive and native prey are affecting species interactions across multiple trophic levels.

Fish growth rates and lake sulphate explain variation in mercury levels in ninespine stickleback (Pungitius pungitius) on the Arctic Coastal Plain of Alaska

Mercury concentrations in freshwater food webs are governed by complex biogeochemical and ecological interactions that spatially vary and are often mediated by climate. The Arctic Coastal Plain of Alaska (ACP) is a heterogeneous, lake-rich landscape where variability in mercury accumulation is poorly understood. Earlier research indicated that the level of catchment influence on lakes varied spatially on the ACP, and affected mercury accumulation in lake sediments. This work sought to determine drivers of spatial variation in mercury accumulation in lake food webs on the ACP. Three lakes that were a priori identified as “high catchment influence” (Reindeer Camp region) and three lakes that were a priori identified as “low catchment influence” (Atqasuk region) were sampled, and variability in water chemistry, food web ecology, and mercury accumulation was investigated. Among-lake differences in ninespine stickleback (Pungitius pungitius) length-adjusted methylmercury concentrations were significantly explained by sulphate concentration in lake water, a tracer of catchment runoff input. This effect was mediated by fish growth, which had no pattern between regions. Together, lake water sulphate concentration and fish age-at-size (proxy for growth) accounted for nearly all of the among-lake variability in length-adjusted methylmercury concentrations in stickleback (R2adj = 0.94, p < 0.01). The percentage of total mercury as methylmercury (a proxy for net Hg methylation) was higher in sediments of more autochthonous, “low catchment influence” lakes (p < 0.05), and in the periphyton of more allochthonous, “high catchment influence” lakes (p < 0.05). The results indicate that dominant sources of primary production (littoral macrophyte/biofilm vs. pelagic phytoplankton) and food web structure (detrital vs. grazing) are regulated by catchment characteristics on the ACP, and that this ultimately influences the amount of methylmercury in the aquatic food web. These results have important implications for predicting future mercury concentrations in fish in lakes where fish growth rates and catchment inputs may change in response to a changing climate.

Phenotypic flexibility in background-mediated color change in sticklebacks.

Phenotypic flexibility may incur a selective advantage in changing and heterogeneous environments, and is increasingly recognized as an integral aspect of organismal adaptation. Despite the widespread occurrence and potential importance of rapid and reversible background-mediated color change for predator avoidance, knowledge gaps remain regarding its adaptive value, repeatability within individuals, phenotypic correlates, and whether its expression is context dependent. We used manipulative experiments to investigate these issues in two fish species, the three-spined stickleback (Gasterosteus aculeatus) and nine-spined stickleback (Pungitius pungitius). We sequentially exposed individuals to dark and light visual background treatments, quantified color change from video recordings, and examined associations of color change with phenotypic dimensions that can influence the outcome of predator-prey interactions. G. aculeatus expressed a greater degree of color change compared to P. pungitius. In G. aculeatus, the color change response was repeatable within individuals. Moreover, the color change response was independent of body size but affected by sex and boldness, with males and bolder individuals changing less. Infection by the parasite Schistocephalus solidus did not affect the degree of color change, but it did modulate its association with sex and boldness. G. aculeatus adjusted the expression of color change in response to predation risk, with enhanced color change expression in individuals exposed to either simulated attacks, or olfactory cues from a natural predator. These results provide novel evidence on repeatability, correlated traits, and context dependence in the color change response and highlight how a suite of factors can contribute to individual variation in phenotypic flexibility.

Population transcriptomics reveals weak parallel genetic basis in repeated marine and freshwater divergence in nine-spined sticklebacks.

The degree to which adaptation to similar selection pressures is underlain by parallel versus non-parallel genetic changes is a topic of broad interest in contemporary evolutionary biology. Sticklebacks provide opportunities to characterize and compare the genetic underpinnings of repeated marine-freshwater divergences at both intra- and interspecific levels. While the degree of genetic parallelism in repeated marine-freshwater divergences has been frequently studied in the three-spined stickleback (Gasterosteus aculeatus), much less is known about this in other stickleback species. Using a population transcriptomic approach, we identified both genetic and gene expression variations associated with marine-freshwater divergence in the nine-spined stickleback (Pungitius pungitius). Specifically, we used a genome-wide association study approach, and found that ~1% of the total 173,491 identified SNPs showed marine-freshwater ecotypic differentiation. A total of 861 genes were identified to have SNPs associated with marine-freshwater divergence, but only 12 of these genes have also been reported as candidates associated with marine-freshwater divergence in the three-spined stickleback. Hence, our results indicate a low degree of interspecific genetic parallelism in marine-freshwater divergence. Moreover, 1,578 genes in the brain and 1,050 genes in the liver were differentially expressed between marine and freshwater nine-spined sticklebacks, ~5% of which have also been identified as candidates associated with marine-freshwater divergence in the three-spined stickleback. However, only few of these (e.g., CLDND1) appear to have been involved in repeated marine-freshwater divergence in nine-spined sticklebacks. Taken together, the results indicate a low degree of genetic parallelism in repeated marine-freshwater divergence both at intra- and interspecific levels.

Ascent Behaviors of Nine-spined Sticklebacks in Orifices and on Overflow Weirs of Fishways

Ascent Behaviors of Nine-spined Sticklebacks in Orifices and on Overflow Weirs of Fishways

Legacy and emerging semi-volatile organic compounds in sentinel fish from an arctic formerly used defense site in Alaska

The Arctic is subject to long-range atmospheric deposition of globally-distilled semi-volatile organic compounds (SVOCs) that bioaccumulate and biomagnify in lipid-rich food webs. In addition, locally contaminated sites may also contribute SVOCs to the arctic environment. Specifically, Alaska has hundreds of formerly used defense (FUD) sites, many of which are co-located with Alaska Native villages in remote parts of the state. The purpose of this study was to investigate the extent of SVOC contamination on Alaska’s St. Lawrence Island through the analysis of sentinel fish, the ninespine stickleback (Pungitius pungitius), collected from Troutman Lake located within the watershed of an FUD site and adjacent to the Yupik community of Gambell. We measured the concentrations of legacy and emerging SVOCs in 303 fish samples (81 composites), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organophosphate esters (OPEs) and their diester metabolites, and per- and poly-fluoroalkyl substances (PFAS). PBDEs and PCBs were the most abundant SVOC groups found in stickleback with ΣPBDE and ΣPCB median concentrations of 25.8 and 10.9 ng/g ww, respectively, followed by PFAS (median ΣPFAS 7.22 ng/g ww). ΣOPE and ΣOPE metabolite concentrations were lower with median concentrations of 4.97 and 1.18 ng/g ww, respectively. Chemical patterns and distributions based on correlations and comparison with SVOC concentrations in stickleback from other parts of the island suggest strong local sources of PCBs, PBDEs, and PFAS on St. Lawrence Island.