Biology subjects

Debes, P. V.

Publications and source records attributed to Debes, P. V..

At least 19 recordsLinked to original sources

bioRxiv2026

High-quality reference genome of the African hermit spider, Nephilingis cruentata, and sex chromosome evolution in spiders

Background: Chromosome-level genome assemblies are increasingly enabling tests of chromosome evolution, conserved synteny, and sex chromosome conservation across diverse animal lineages, including spiders. Results: Here, we present a chromosome-level genome assembly for the African hermit spider, Nephilingis cruentata, a species with extreme female-biased sexual size dimorphism and a cytogenetically inferred XX2 sex chromosome system. The final Hi-C-assisted assembly spans 1.72 Gbp, with 99.5% of bases assigned to 13 pseudochromosomes, a scaffold N50 of 131.6 Mbp, and a BUSCO completeness score of 98.8%. We annotated 20,021 protein-coding genes, and repetitive elements accounted for 42.7% of the genome. Sex-specific whole-genome resequencing identified Chr02 and Chr07 as candidate X chromosomes based on reduced male coverage, consistent with the expected XX2 system. Using comparative whole-genome alignments across existing chromosome-scale spider assemblies, we also show that sex-linked chromosomes retain broad homologous identity across sampled spider lineages but exhibit lower synteny conservation and greater chromosome-length divergence than autosomes. Conclusions: These results suggest that spider sex chromosomes are conserved in homologous identity but more labile in structure, providing a comparative framework for studying sex chromosome conservation and divergence across Araneae.

genomics↗

bioRxiv2026

Two-tower models for genomic prediction of reproductive outcomes and sex-specific fertility liabilities: simulation insights

Many biological characteristics arise by interactions between more than one biological organism or unit. Fertilization success in sexually reproducing species represents such an extended phenotype where both mates are required to be fertile for a successful outcome. Consequently, predictive models should account for the joint nature of reproductive performance while offering interpretable estimates for individual mate contributions. Recent advances in genomics and machine learning (ML) provide standardized, high-dimensional genetic information on one hand and computational tools capable of modeling complex biological systems on the other. Here, we construct and evaluate two-tower (TT) machine learning architectures for genomic prediction of binary reproductive outcomes and recovery of sex-specific fertility liabilities. Simulated datasets, generated under a range of genetic architectures, were utilized to compare multilayer perceptron (TT-MLP), convolutional neural network (TT-CNN), and L1-regularized linear (TT-LASSO) two-tower models. Simulation scenarios varied sex-specific heritabilities, genetic correlations, infertility prevalence, mating structure, and sex-specific infertility rates. Models were evaluated with regard to their ability to predict reproductive success at pair level and also recover true underlying genetic values for male and female fertility. Prediction accuracy increased with the underlying heritable component as expected, while sex-specific tower-scores successfully recovered latent fertility liabilities despite models being trained only on observed joint outcomes. TT-LASSO achieved the highest overall classification performance, whereas TT-MLP provided more balanced and consistent recovery of sex-specific genetic values across scenarios. An additional simulation, incorporating genotype-dependent mate compatibility demonstrated advantages of fully-connected neural networks for capturing non-additive interactions. These results indicate that two-tower frameworks provide a powerful approach for modeling reproductive traits, enabling simultaneous prediction of aggregate reproductive outcomes and sex-specific fertility liabilities from genotypic information.

genetics↗

bioRxiv2025

It is complicated: how sex, family, and season affect growth in a sexually size-dimorphic spider

Female-biased sexual size dimorphism (SSD), where females are larger than males, is widespread. While ultimate explanations for SSD are well established, the proximate developmental mechanisms remain poorly understood. Studying sex-specific growth trajectories to identify common vs. sex-specific growth periods is therefore key to uncovering when and how SSD emerges. Theory predicts that female-biased SSD may arise if females hatch larger, grow more rapidly, grow longer, or combine these pathways. We studied sex-specific growth trajectories in the African hermit spider, Nephilingis cruentata, where adult females are on average 75-times heavier and take 2.3-times longer until adulthood than males. We tracked growth trajectories of carapace width for 916 individuals. After initial growth trajectories common to both sexes, trajectories diverged after [~]80 days, coinciding with the onset of the male subadult stage. At this point, male growth decelerated and terminated at sexual maturity, whereas female growth accelerated until their subadult stage at [~]200 days. Thereafter, female growth rate also decelerated and eventually terminated at sexual maturity. Thus, females attain their larger size through both an extended growth period and a more rapid growth rate, which initiates in mid-development. Whereas we detected seasonal effects on growth that were similar in both sexes, family effects showed strong sex-specific signatures. Our results pinpoint a key developmental window in which male and female growth trajectories begin to diverge, providing a clear target for detailed investigation of the mechanisms underlying SSD. At the same time, the complexity of these patterns will likely hinder mechanistic studies of SSD development.

zoology↗

bioRxiv2025

Genetic parameters and sex-specific architecture of observed and latent fertility phenotypes in a closed breeding nucleus of an Arctic salmonid

Successful reproduction is a key factor for efficient breeding schemes and sustainable animal farming. Aquaculture breeding programs rely heavily on small fractions of selected breeders to yield large production stocks, given the high fecundity typically observed in these species. In Sweden, Arctic charr (Salvelinus alpinus) is a salmonid with notable commercial potential, with a selective breeding program operating for ten generations under a growth-rate focused breeding goal. Despite significant gains, the nucleus faces challenges with low and fluctuating fertility impeding expansion efforts. In this study, we estimate genetic parameters for charr milt quality phenotypes measured with specialized cytometry and Computer-Assisted Sperm Analysis (CASA). At the same time, we assess the sex-specific architecture governing egg count and sperm concentration along body size. Finally, we propose a novel analytical framework for the analysis of realized fertilization success rates by considering a multiplicative system of latent maternal and paternal contributions. Low to moderate heritability estimates and genetic correlations were obtained from multi-trait modelling for traits reflecting sperm quality along with high estimates for fork length. Genetic correlations among sperm kinematic parameters appeared strong, while the same traits showed weak positive and weak negative correlations with sperm concentration and fork length, respectively. Furthermore, a negative genetic correlation between sperm concentration and both male body size and egg count suggests a complex interplay of a possible trade-off and sexual antagonism. Our latent fertility analytical approach returned low to moderate heritability estimates depending on the modelling configuration. Overall, our study demonstrated the complexity characterizing the heritable portions of reproductive traits in Arctic charr and tested alternative tools that have the potential for integration into selective breeding programs.

genetics↗

bioRxiv2025

Testicular gene expression patterns suggest a heterochronic shift underlying vgll3-mediated maturation age variation in Atlantic salmon

Heterochrony, or shifts in developmental timing, drives phenotypic diversity within and between species and shapes life history traits that can be selected for in changing environments which in turn promotes population resilience. Despite its importance, the molecular basis of heterochrony remains largely unknown. Mutations in "heterochronic genes" that regulate these processes can induce stable timing shifts, impacting important life history traits like pubertal timing. Heterochronic shifts in gene transcription are often tissue-specific and in mammals, for example, the testis shows the most pronounced heterochrony across species, especially during spermatogenesis. Age at maturity is a key adaptive trait across species, with vgll3, a Hippo pathway co-factor, as a main determinant in Atlantic salmon. The roles of vgll3 in maturation timing, adiposity, and energy storage are evolutionarily conserved across fish and mammals. Recent studies in salmon show vgll3 alleles; early (E) and late (L), affect reproductive gene expression, reinforcing its role in regulating developmental timing. This study examines whether vgll3 influences testicular heterochrony in Atlantic salmon by analyzing Hippo pathway-related gene expression in E and L genotypes. We observed heterochronic divergence in Hippo pathway gene transcription, indicating accelerated spermatogenesis-linked changes in the testes of vgll3*EE individuals. Since maturation in Atlantic salmon is closely tied to environmental changes, and the Hippo pathway acts as an environmental sensor, these findings suggest that Hippo-vgll3 shifts may also respond to environmental signals. This positions vgll3 as a heterochronic gene which is potentially affected by environmental changes (heterokairic), making it an ideal target for studying ecological adaptation linked to heterochrony.

developmental biology↗

bioRxiv2024

Food quality and vgll3 genotype influence reproductive traits in female Atlantic salmon

Age at maturity is an important factor contributing to life-history diversity. In Atlantic salmon, this trait often shows sex-specific variation, but female salmon are seldom included in experimental studies of maturation. As a result, there is a gap in our knowledge of how different genetic and environmental factors affect female maturation. Using a 4-year common-garden experiment, we assessed the influence of diet (low-fat vs. control) and vgll3 (a candidate gene in a genomic region known to influence age at maturity in Atlantic salmon) on maturation and related phenotypic traits of female Atlantic salmon from two 2nd-generation hatchery populations. We found the early-maturation-associated vgll3*E allele to be associated with higher probability of maturation. Heritability of maturation was estimated to be 0.295 with vgll3s contribution to phenotypic variance being [~]2%. In addition, both body size and body condition measured in the spring prior to spawning influenced maturation. Body condition, in turn, was influenced by population and diet. The northern Oulu population and the low-fat diet were associated with lower body condition compared to the southern Neva population and the control diet. Moreover, there was an interaction between population and diet on body condition, suggesting that populations may respond differently to nutrient availability. These results broaden our understanding of the processes underlying maturation and demonstrate that genes and environment interact to shape age at maturity in female Atlantic salmon.

evolutionary biology↗

bioRxiv2024

Large effect life-history genomic regions are associated with functional morphological traits in Atlantic salmon

Understanding pleiotropic architectures of phenotypes is instrumental for identifying the functional basis of adaptive genetic variation in the wild. Life-history variation may have a morphological basis that mediates resource acquisition allocation pathways, but identifying the underlying genetic basis of such traits is challenging. Using Atlantic salmon juveniles reared in common garden conditions, we test if two life-history associated loci in Atlantic salmon, six6 and vgll3, are also associated with functional morphological traits. These loci had previously shown to exhibit strong signals of adaptation and are highly correlated with sea age at maturity. We show that genetic variation at the vgll3 locus is linked to variation in morphological traits that underlie swimming performance, along a trade-off axis between efficient cruising and maneuvering, while the genetic variation at the six6 locus was linked to variation in body-head proportions suggesting the potential functional importance of these traits for resource acquisition efficiency. However, the direction of changes in morphological traits associated with late-vs. early-maturing alleles was not always consistent with the expected direction of an effect to maturation timing. Our results reveal a complex morphological landscape associated with the genetic variation in these loci, possibly as a result of pleiotropy or linkage across these genomic regions.

ecology↗

bioRxiv2024

Hippo-vgll3 signaling may contribute to sex differences in Atlantic salmon maturation age via contrasting adipose dynamics

Sexual maturation in Atlantic salmon entails a transition in energy utilization, governed in part by genes and environmental stimuli in sex-specific manner. Salmon males require less energy, in the form of adiposity, to mature compared to females and typically mature younger. Maturation age is also influenced in a sex-dependent fashion by the vgll3 genotype (vestigial-like 3), a co-factor in the Hippo pathway. The underlying molecular processes of sex-dependent maturation age, and how they interplay with adiposity and vgll3 genotypes, have remained unknown. To elucidate the molecular mechanisms underlying sex- and genotype-specific maturation differences, we investigated the association of early (E) and late (L) maturation vgll3 alleles and the transcriptional expression of > 330 genes involved in the regulation of the Hippo pathway and sexual maturation, and related to molecular signals in brain, adipose tissue, and gonads. The strongest effect of vgll3 genotype was observed in adipose tissue for females and in brain for males, highlighting a sex-specific expression difference in the main association of vgll3 genotype. Genes related to ovarian development showed increased expression in vgll3*EE compared to vgll3*LL females. Additionally, vgll3*EE females compared to vgll3*EE males exhibited reduced markers of pre-adipocyte differentiation and lipolysis yet enhanced expression of genes related to adipocyte maturation and lipid storage. Brain gene expression further showed sex-specific expression signals for genes related to hormones and lipids, as well as tight junction assembly. Overall, these sex-specific patterns point towards a greater lipid storage and slower energy utilization in females compared to males. These results suggest that Hippo-dependent mechanisms may be important mediators of sex differences in maturation age in salmon.

genetics↗

bioRxiv2024

A salmon fish model reveals genetic signals in brain associated with early maturation

Emerging evidence suggests a link between adiposity and early maturation, potentially impacting hormonal signaling pathways governing puberty timing. Fish models have proven invaluable in studying these processes, given their genetic and physiological similarities to humans. In Atlantic salmon, in addition to being linked with environmental shifts and lipid reserves, the timing of sexual maturation also has a strong genetic basis. A gene encoding a co-factor of Hippo pathway, vgll3, is a major determinant of maturation timing in salmon, and the same gene was found to be associated with maturation timing in humans. Intriguingly, vgll3 also inhibits adipogenesis in mice. Recent studies in salmon revealed correlations between vgll3 genotypes and reproductive axis gene expression, possibly modulated through the Hippo signaling pathway. The Hippo pathway is known for its role in sexual maturation and adipogenesis and responds to environmental cues such as dietary fat and temperature. In this study, we employed a custom gene expression panel in male Atlantic salmon with different vgll3 early (E) and late (L) maturation genotypes testing components of this pathway in brain at immature and mature stages. We found increased brain expression of a major Hippo pathway kinase (lats1b) and melanocortin receptor encoding genes (mc4ra and mc4rc) in individuals with early (E) maturation genotypes of vgll3 before maturation development of testes. Moreover, we found components and interacting partners of Hippo pathway showing differential expression in brain of individuals with early (E) and late (L) vgll3 genotypes prior to maturation. This could indicate extensive and complex roles of Hippo pathway in brain processes required for preparing for [the onset of] maturation at upstream of reproductive axis. This study elucidates molecular mechanisms underpinning early maturation, and for the first time in fish, offering insights into detecting it at molecular level in brain before visible gonadal changes occur.

genetics↗

bioRxiv2024

A complex mechanism translating variation of a simple genetic architecture into alternative life-histories

Linking genes to traits is a central goal in biology. Despite progress in discovering genes associated with trait differences, a poor understanding of the functional mechanisms underlying genetic associations leaves us critically far from connecting genetic and phenotypic variation. This knowledge-gap is particularly large in multifaceted phenotypes of ecological relevance such as life-history traits. Using a multiomic dissection of the genotype-phenotype association in a large-effect maturation age gene - the transcription cofactor vestigial-like 3 (vgll3) - in Atlantic salmon (Salmo salar), we show that vgll3 mediates concerted changes of distinct molecular phenotypes associated with puberty in male gonads. Vgll3 genotype conferring early maturity upregulates key genes controlling androgen production, cellular energy and adiposity, and TGF-{beta} signaling, among others, thereby increasing the likelihood of earlier pubertal initiation. Genotype-dependent developmental trajectories are produced through VGLL3 interaction with distinct transcription factors, thus coordinating differential activation of regulatory pathways. These results reveal a genetically simple, yet functionally complex, architecture underlying alternative life-histories where variation in a single major effect gene produces pleiotropic variation in a spectrum of cellular traits. Our results further suggest that evolution in correlated phenotypes such as exemplified by alternative life history strategies may be mediated by a surprisingly simple genetic architecture.

evolutionary biology↗

bioRxiv2023

Gene co-expression patterns in Atlantic salmon adipose tissue provide a molecular link between seasonal changes, energy balance and age at maturity

Sexual maturation in many fishes requires a major physiological change that involves a rapid transition between energy storage and usage. In Atlantic salmon, this transition for the initiation of maturation is tightly controlled by seasonality and requires a high-energy status. Lipid metabolism is at the heart of this transition since lipids are the main energy storing molecules. The balance between lipogenesis (lipid accumulation) and lipolysis (lipid use) determines energy status transitions. A genomic region containing a transcription co-factor of the Hippo pathway, vgll3, is the main determinant of maturation timing in Atlantic salmon. Interestingly, vgll3 acts as an inhibitor of adipogenesis in mice and its genotypes are potentially associated with seasonal heterochrony in lipid storage and usage in juvenile Atlantic salmon. Here, we explored changes in expression of more than 300 genes directly involved in the processes of adipogenesis, lipogenesis and lipolysis, as well as the Hippo pathway in the adipose tissue of immature and mature Atlantic salmon with distinct vgll3 genotypes. We found molecular evidence consistent with a scenario in which immature males exhibiting vgll3 genotype specific seasonal direction of change in their lipid profiles. We also identified components of the Hippo signaling pathway as potential major drivers of vgll3 genotype specific differences in adipose tissue gene expression. This study demonstrates the importance of adipose gene expression patterns for directly linking environmental changes with energy balance and age at maturity through genetic factors bridging lipid metabolism, seasonality and sexual maturation.

physiology↗

bioRxiv2023

Genotype-specific variation in seasonal body condition at a large-effect maturation locus

O_LIOrganisms utilize varying lipid resource allocation strategies as a means to survive seasonal environmental changes and life-history stage transitions. In Atlantic salmon, a certain lipid threshold is needed to initiate sexual maturation. Because of this, an individuals maturation schedule may be affected by changes in temperature and food availability across the seasons that create natural fluctuations of lipid reserves. C_LIO_LIRecent studies have found a genome region, including the gene vgll3, that explains a large proportion of variation for size and age at maturity. Vgll3 encodes a transcription co-factor that acts as an inhibitor of adipogenesis in mice and also affects condition factor and other phenotypes in juvenile salmon. However, even with many studies investigating varying temperature effects, there is a lack of temporal studies examining the effects of seasonality on such phenotypes, nor have the effects of vgll3 genotype on condition factor and maturation in different temperatures at different life stages. C_LIO_LIHere, we investigate the influence of different larval and juvenile incubation temperatures, vgll3 genotype and their interactions on juvenile salmon phenotypes including body condition, and sexual maturation rate. We reared Atlantic salmon for 2 years in varying temperatures with an average 1.76 {degrees}C difference between warm and cold treatments in four different larval-juvenile phase treatment groups (Warm-Warm, Warm-Cold, Cold-Warm, and Cold-Cold) until the first occurrence of maturation in males. C_LIO_LIWe found no effect of larval temperature on the measured phenotypes or maturation rate, suggesting the occurrence of growth compensation over the course of the experiment. Agreeing with previous studies, an increased maturation rate was observed in individuals of the warm juvenile temperature treatment. C_LIO_LIIn addition, we observed differences in condition factor associated with vgll3 genotype, whereby vgll3*EE individuals (the genotype associated with early maturation) had a less variable condition factor across the seasons compared to the vgll3*LL (associated with late maturation) individuals. C_LIO_LIThis result suggests a vgll3 influence on resource acquisition and allocation strategies, possibly linked with the early maturation process, with individuals carrying the early maturation vgll3 genotype having a higher early maturation rate and a higher condition factor in the spring. C_LI

evolutionary biology↗

bioRxiv2022

Sexual conflict mitigation via sex-specific trait architecture

Sexual dimorphism -- the sex-specific trait expression -- may emerge when selection favours different optima for the same trait between sexes, i.e., under antagonistic selection. Intra-locus sexual conflict exists when the sexually dimorphic trait under antagonistic selection is based on genes shared between sexes. A common assumption for sexual-size dimorphism (SSD) is that its presence indicates resolved sexual conflict, but how current sex-specific evolution proceeds under sexual dimorphism remains enigmatic. We investigated whether a sex-specific architecture of adult body size explains sexual conflict resolution under extreme SSD in the African hermit spider, Nephilingis cruentata, where adult female body size greatly exceeds that of males. Specifically, we estimated the sex-specific importance of genetic and maternal effects on adult body size among individuals that we laboratory-reared for up to eight generations. Quantitative genetic model estimates indicated that size variation in females is to a larger extent explained by direct genetic effects than by maternal effects, but in males to a larger extent by maternal than by genetic effects. We conclude that this sex-specific body-size architecture enables body-size evolution to proceed much more independently than under a common architecture to both sexes, thereby mitigating sexual conflict under SSD.

evolutionary biology↗

bioRxiv2022

Temperature and dietary energy content influence female maturation age and egg nutritional content in Atlantic salmon

The environment experienced by a female influences reproductive traits in many species of fish. Environmental factors such as temperature and diet are not only important mediators of female maturation and reproduction but also of egg traits and offspring fitness through maternal provisioning. In this study, we use three-year-old, tank-reared, Atlantic salmon from two Finnish populations to investigate the effect of temperature and diet on maturation and egg traits. We show that a temperature difference of 2{degrees}C is sufficient to delay maturation in female Atlantic salmon whereas a 22% reduction in dietary energy content had no effect on maturation. Diet did not influence the body size, condition, or fecundity of the mature females or the size or protein content of the eggs. However, a higher energy diet increased egg lipid content. Neither female body size nor condition were associated with egg size or fat/protein composition. Our results indicate that female salmon that have a poorer diet in terms of energy content may have a reproductive disadvantage due to lower energy provisioning of eggs. This disadvantage has the potential to translate into fitness consequences for their offspring.

ecology↗

bioRxiv2022

Adipose tissue mitochondrial respiration in Atlantic salmon: implications for sex-dependent life-history variation

Adipose tissue is essential for energy homeostasis, with mitochondria having a central role in its function. Mitochondria-mediated white adipose tissue dysfunction has been linked to several metabolic disorders in humans but surprisingly little is known about natural variation in mitochondrial function in wild animal populations, and its evolutionary significance. Early sexual maturation (low age-at-maturity) in Atlantic salmon (Salmo salar) is promoted by higher adiposity and has a strong genetic association with the vgll3 locus. This makes Atlantic salmon a convenient wild model to study the potential role of mitochondria-mediated adipose tissue processes in relation to the timing of maturation. Yet, mitochondrial respiration has not been measured in the adipose tissue in fish, and the lack of data is restricting the development of informed hypotheses. Here, using 13 Atlantic salmon individuals reared in common-garden conditions, we first verified the feasibility of measuring mitochondrial respiration in the adipose tissue. As expected, the respiration level was generally low, but nonetheless we successfully quantified its biological variation in the adipose tissue. Next, we analysed the potential association of mitochondrial respiration with mitochondrial DNA (mtDNA) content, adipocyte size, sex, and the vgll3 genotype. Despite low samples sizes, mitochondrial respiration, leak respiration, and coupling capacity (P/E ratio) were marginally significantly decreased in immature females carrying with the vgll3 early maturation compared to the alternative genotype. Based on these results, we suggested two new hypotheses on how the coupling capacity of oxidative phosphorylation could be linked with the timing of maturation via adiposity and pave the way to study the mechanistic relationships between life-history variation and mitochondrial bioenergetics in wild populations.

physiology↗

bioRxiv2022

Strong effects of temperature, population and age-at-maturity genotype on maturation probability for Atlantic salmon in a common garden setting

O_LIAge at maturity is a key life history trait and involves a trade-off between survival risk and reproductive investment, has close connections to fitness, and is an important factor for population structures. Temperature can have a dramatic influence on life history in ectotherms, but this influence may differ between populations. While an increasing number of studies have examined population-dependent reactions with temperature, few have investigated this in the context of maturation timing. C_LIO_LIAtlantic salmon is a highly relevant study species for improving understanding of this topic as it displays considerable variation in life-history strategies, including maturation timing. Additionally, a large amount of this variation in maturation timing has been associated with a genomic region including the strong candidate gene vgll3, but the effect of this gene in the context of different environments and populations has not been studied. C_LIO_LIUsing a large-scale common-garden experiment, we find strong effects of temperature, population, and vgll3 genotype on maturation in 2-year-old male Atlantic salmon. Observed maturation probability was 4.8 times higher in individuals reared at a mean temperature of 8.6{degrees}C compared to 6.9{degrees}C. This temperature effect was population-specific and was higher in the southern population compared to the northern population, potentially due to a higher intrinsic growth in the southern population as well as growth-temperature interaction. C_LIO_LIThe early-maturation vgll3*E associated with a significantly higher maturation probability, but there was no vgll3-interaction with temperature or population. C_LIO_LIBoth body condition and body mass associated strongly with maturation; the body-condition association was stronger in fish carrying the vgll3*E allele, and the body mass association was only present in the warm treatment. C_LIO_LIOur findings demonstrate that the relative effect of vgll3 on maturation timing is similar for two populations and two thermal environments and gives new perspectives on the relative effect of vgll3 compared to such influences. Additionally, we show that populations can vary in their response to temperature change in terms of maturation timing, and that high intrinsic growth could potentially be associated with higher thermal sensitivity for life history variation. C_LI

evolutionary biology↗

bioRxiv2021

Life-history genotype explains variation in migration activity in Atlantic salmon (Salmo salar).

One of the most important life-history continuums is the fast-slow axis, where "fast" individuals mature earlier than "slow" individuals. "Fast" individuals are predicted to be more active than "slow" individuals; high activity is required to maintain a fast life-history strategy. Recent meta-analyses revealed mixed evidence for such integration. Here, we test whether known life-history genotypes differ in activity expression by using Atlantic salmon (Salmo salar) as a model. In salmon, variation in Vgll3, a transcription co-factor, explains [~]40% of variation in maturation timing. We predicted that the allele related to early maturation (vgll3*E) would be associated with increased activity. We used an automated surveillance system to follow [~]1900 juveniles including both migrants and non-migrants (i.e. smolt and parr fish, respectively) in semi-natural conditions over 31 days ([~]580 000 activity measurements). Against our prediction, vgll3 did not explain variation in activity in pooled migrant and non-migrant data. However, in migrants, vgll3 explained variation in activity according to our prediction in a sex-dependent manner. Specifically, in females the vgll3*E allele was related to increasing activity, whereas in males the vgll3*L allele (later maturation allele) was related to increasing activity. These sex-dependent effects might be a mechanism maintaining within-population genetic life-history variation.

evolutionary biology↗

bioRxiv2020

Sex-specific lipid profiles in muscle of Atlantic salmon juveniles

Energy allocation in juvenile fish can have important implications for future life-history progression. Inherited and environmental factors determine when and where individuals allocate energy, and timely and sufficient energy reserves are crucial for reaching key life stages involved in the timing of maturation and sea migration. In Atlantic salmon, lipid reserves are predominantly found in the viscera and myosepta in the muscle and have been shown to play a key role in determining the timing of maturity. This life-history trait is tightly linked to fitness in many species and can be different between males and females, however, the details of relative energy allocation in juveniles of different sexes is not well understood. Therefore, the aim of this study was to investigate the effects of sex, genetics and environment during juvenile development of salmon on the amount and composition of their lipid reserves. To do so, juvenile salmon were fed one of two different lipid food contents during their first summer and autumn under common-garden conditions. Muscle lipid composition and concentrations were determined by thin layer chromatography. The muscle lipid class concentrations covaried negatively with body length and males showed higher concentrations than females for phosphatidylcholine, cholesterol, sphingomyelin, and triacylglycerol. This sex-specific difference in major lipid classes presents a new scope for understanding the regulation of lipids during juvenile development and gives direction for understanding how lipids may interact and influence major life-history traits in Atlantic salmon.

molecular biology↗