Journal of Experimental Zoology Part B: Molecular and Developmental Evolution

Regenerative capacity varies widely across flatworms (Platyhelminthes). Whereas catenulids, microstomids and planarians can regenerate a complete head de novo, other flatworms cannot. This striking diversity raises a longstanding evolutionary question: does whole-body regeneration represent an ancestral trait that was subsequently lost in multiple lineages, or did it evolve convergently? Addressing this question requires comparative analyses of the molecular mechanisms underlying regeneration across phylogenetically diverse flatworms. Here, we focus on Wnt signaling, a deeply conserved regulator of antero-posterior (A-P) patterning and a central determinant of head-versus-tail identity during planarian regeneration, to establish a mechanistic framework for such comparisons. Although Wnt signaling has been studied extensively in planarians and parasitic neodermatans, its evolution and deployment in other flatworm clades remain poorly characterized. To address this gap, we characterized the complement of Wnt signaling components in two early-diverging flatworm clades, Catenulida and Macrostomorpha, with particular emphasis on expression and function in the catenulid Stenostomum brevipharyngium. Phylogenetic analyses reveal the ancient loss of six Wnt families and one secreted Frizzled-related protein (sFRP) family in the last common ancestor of flatworms, followed by additional lineage-specific gene losses and expansions. Moreover, several Wnt pathway components display markedly divergent expression patterns between catenulids and other flatworms, while functional analyses indicate corresponding differences in their regenerative deployment. Together, our findings reveal a dynamic evolutionary history of the flatworm Wnt signaling toolkit and establish a comparative framework for testing whether the molecular circuitry underlying head regeneration is ancestrally conserved or has evolved independently in distinct flatworm lineages.

Indomethacin and temperature shocks are both widely used to induce ephyra production in Cassiopea polyps, yet the combined effect of these stimuli on strobilation rate, ephyra viability, and polyp survivorship has not been systematically examined. We designed a full factorial experiment crossing five indomethacin concentrations (0, 10, 25, 50, and 75 {micro}M) with four temperature treatments (22, 25, 28, and 31{degrees}C) across three independent experimental trials, exposing a total of 288 individual Cassiopea xamachana polyps for 29 days. Overall, 207 of 288 polyps (71.9%) released at least one ephyra. Temperature was the stronger predictor of strobilation: higher temperatures substantially increased the probability of producing a healthy ephyra (log-odds: +0.327 per {degrees}C; {chi}{superscript 2} p = 6.5 x 10-5), while indomethacin had a smaller but significant positive effect (log-odds: +0.024 per {micro}M; {chi}{superscript 2} p = 0.035). The two stimuli acted independently without significant interaction on healthy ephyra production ({chi}{superscript 2} p = 0.87), although their interaction on total ephyra production (including unhealthy releases) was significant ({chi}{superscript 2} p = 1.0 x 10-9). Notably, low indomethacin concentrations (10 and 25 {micro}M) significantly increased the proportion of unhealthy ephyrae relative to seawater controls (paired t-tests: p = 0.035 and p = 0.006, respectively), while higher concentrations (50-75 {micro}M) did not. Polyp survivorship declined significantly at 28{degrees}C and 31{degrees}C but was unaffected by indomethacin. Trial replicate was the most statistically significant predictor of every outcome measured with the third trial producing near-universal strobilation but zero viable ephyrae, a result of an unidentified perturbation. These results indicate that temperature elevation to 28-31{degrees}C is the most reliable induction strategy for C. xamachana and that low indomethacin concentrations should be avoided when ephyra quality is paramount. We also note that cryptic batch-level variables can overwhelm controlled factors and should be addressed in future experimental designs.

Quantifying skeletal mineralization phenotypes in larval fish is complicated by the natural curvature of the notochord and by sample-to-sample variability in orientation, staining and imaging. Consequently, many studies rely on summary measures such as vertebral counts or total stain intensity. Here we present SCAMP (Spinal Calcification & Mineralization Profiler), an open-source, GUI-based Python tool that computationally straightens the curved notochord of Alizarin Red S-stained fish larvae and generates standardized mineralization profiles along the spinal axis. This approach reduces positional and shape variability, allowing direct, quantitative comparison of calcification patterns within and between experimental cohorts, without requiring programming expertise. We validate SCAMP using a zebrafish model of Pseudoxanthoma elasticum (abcc6aelu15/elu15), recovering genotype-specific differences in the intensity, extent and spatial distribution of ectopic calcification. Using SCAMP, we further show that inorganic pyrophosphate (PPi) supplementation of the medium suppresses ectopic notochord calcification, alters the anterior-posterior distribution of mineralized regions in homozygous mutants, and promotes mineralization at physiological vertebral sites. We also show that methylene blue, a routine antifungal additive in fish medium, reduces baseline calcification, with the most pronounced effects observed in heterozygous controls. SCAMP is freely available and has the potential to be adapted to other fish species used in skeletal and mineralization research.

Sea urchins are pivotal models in cellular and developmental biology, but their biphasic life cycle with an extended larval life limits the ability to study post-metamorphosis and adult characters. Here, we introduce a genomically-enabled model system, the tuxedo urchin Mespilia globulus, which has rapid access to late life stages in sea urchins. We describe how we cultured M. globulus in a landlocked marine facility, raised larvae under artificial conditions and closed their life cycle. We established the experimental tractability of M. globulus: we labelled transcripts by hybridization chain reaction (HCR), and knocked out pigmentation genes to produce albino larvae using CRISPR/Cas9. We generated chromosome-scale genome assemblies for two individuals representing both sexes and two color morphs (red and blue), and compared the organisation of the 21 chromosomes of M. globulus with that of other camarodont echinoid models. We determined that M. globulus showed a conservative gene repertoire lacking the gene family expansions seen in other camarodont sea urchins. We annotated the complement of genes associated with pigmentation, immune and nervous systems and profiled their expressions in tissues and organs. Finally, we surveyed sex-related regions in genomes using genome assemblies and resequencing data, finding no evidence of heteromorphic sex chromosomes in M. globulus. Our findings highlight the accessibility of this new sea urchin model for studying the metamorphosis and adult biology of sea urchins.

The nautilus (Nautilus sp.) is an early-branching cephalopods. It retains several conchiferan synapomorphies, including an external planispiral biomineralized shell. The shells complex structure allows it to withstand hydrostatic pressure, control buoyancy, and protect against external hazards. In this study, we comprehensively examined shell microstructures across different shell components and regions representing various ontogenetic stages in two adult museum shell specimens. We found that the nautilus shell is composed of five microstructural types (spherulitic, prismatic, nacreous, semi-prismatic, and irregularly oriented prismatic structures) organized into layered architectures within individual shell components and coordinated across the shell as an integrated system. Our observations highlight transitions between distinct microstructures within and across shell components and local variation within individual components such as the dorsal and ventral shell walls, suggesting that these patterns may contribute to shell strength and overall mechanical performance. Variation in caecum morphology suggests that this structure may be developmentally plastic and subject to relatively relaxed structural constraints. These findings show that the Nautilus shell is an integrated biomineral system in which diverse microstructures are organized across shell components to meet functional demands and provide the mechanical strength needed for survival.

Parental ageing can influence offspring through non-genetic mechanisms. The contribution of epigenetic inheritance parental effects still remains poorly understood. DNA methylation is a widespread regulator of gene expression that changes during development and ageing and can also act as a mediator of intergenerational effects. We tested whether age-related changes in parental DNA methylation are transmitted to offspring in the short-lived turquoise killifish (Nothobranchius furzeri, Cyprinodontiformes). Using reduced-representation sequencing, we quantified genome-wide DNA methylation and examined methylation dynamics at individual loci. The overall proportion of methylated CpG sites increased during early ageing but declined at later ages, revealing a non-linear trajectory with substantial among-individual variation. Despite these age-related changes, we found no evidence that parental methylation patterns were transmitted to offspring, either at the genome-wide level or at individual loci. Our findings indicate that although DNA methylation undergoes pronounced age-dependent remodelling in adult killifish, these changes are not detectably inherited by the next generation. We discuss these results in the context of epigenetic inheritance and ageing in vertebrate model systems.

Hard cornification is the developmental process that produces the hardened epidermal structures that characterize tetrapod diversity, including scales, feathers, hair, and claws. This process relies on keratin proteins and additional reinforcing proteins that assemble, cross-link, and strengthen tissues to become mechanically resilient. Although the molecular composition of hard cornified tissues is known to vary among tetrapods, the program is least understood in amphibians. Within frogs, hard cornification occurs in the mouthparts of most tadpoles and in the nuptial pads, hindfoot claws, and foot tubercles of some adults. We characterized transcriptomic profiles of Bombina orientalis tadpoles at three developmental stages before, during, and after mouthpart cornification. We identified 25 keratin genes orthologous to amniote hard keratins in the B. bombina genome, 18 of which are upregulated in cornifying larval mouthparts. Furthermore, two of these hard keratin paralogs and an amphibian epidermal differentiation gene exhibit distinct spatial expression patterns within the jaw sheaths and keratodonts evidenced by in situ hybridization, suggesting they have discrete functional roles. The newly discovered diversity of the hard keratin repertoire in Bombina , and the concurrent expression of many of these paralogs in tadpole mouthparts, suggests that anuran hard cornification is much more complex than adult cornified traits thus far characterized in Xenopus frogs. Our results also challenge the notion that the diversification of keratins in Amphibia is primarily associated with the transition to more terrestrial habits, and may instead be shaped, in part, by the novel feeding apparatus of aquatic tadpoles.

The influences of the gut microbiome on animal physiology are well-documented, yet the developmental timing of microbial colonization and its long-term consequences remain poorly understood. In this study, we investigated how the timing of bacterial colonization during development affects transcriptional programming and phenotypic outcomes in adult Drosophila melanogaster reared on a common, rich diet. Using RNA-seq analysis on whole flies colonized either as newly hatched larvae or as newly eclosed adults, we observed minor but distinct transcriptional responses dependent on when flies were colonized. Both embryonic and adult colonization were associated with ~ 25 to ~ 200 differentially expressed genes compared to axenic controls, with the majority upregulated and enriched for immune-response genes, suggesting that colonization establishes a broader immune competence. However, only 10 genes showed persistent differential expression that was not normalized by introducing bacteria to adult axenic flies, including mitochondrial genes, the adipokinetic hormone (Adh), and a putative secreted neuropeptide. Overall, these findings suggest that Drosophila development on a rich diet is largely robust to the timing of bacterial colonization but that certain metabolic effects may occur.

The teleost whole-genome duplication (TGD) contributed to functional diversification of opsins. Some TGD paralogs, including those of parapinopsin (PP), Vertebrate Ancient (VA) opsin, and long wavelength-sensitive (LWS) opsin, show different absorption spectra and/or expression patterns. However, our knowledge of detailed evolutionary processes and mechanisms by which TGD contributed to opsin diversification is still limited. Here, we report that TGD paralogs of parietopsin (PT1 and PT2) are retained in extant species. While most species, including the zebrafish, have only PT1, several characins, including the red piranha (Pygocentrus nattereri), retain both PT1 and PT2. The Mexican tetra (Astyanax mexicanus) and catfishes have only PT2. To assess the degree of functional diversification between PT1 and PT2, we characterized spectral properties and expression patterns. Maximum absorption spectra differ slightly among PTs. Those of red piranha PT1, PT2, Mexican tetra PT2, and Japanese catfish (Silurus asotus) PT2 were located at 517 nm, 528 nm, 517 nm, and ~535 nm, respectively. Fluorescence in situ hybridization showed that (1) piranha PT1 and PT2 are expressed in the same pineal cells, and (2) they are also co-expressed with PP1. Based on these findings, functional diversification of opsins after gene duplication is discussed.

The physiology of ectotherms can change substantially during acclimation to changing environmental temperature. The role of transcription in acclimation responses has been well-established, but it remains unclear whether transcriptional regulation generally reflects abrupt changes after surpassing temperature thresholds, or whether transcript abundance is a relatively monotonic, continuous function of acclimation temperature. In this study we exposed adult male Drosophila subobscura flies to four different 96-hour acclimation treatments at temperatures that were not acutely stressful but ranged from relatively cold (10{degrees}C) to relatively warm (27{degrees}C) with respect to standard rearing conditions. Transcriptome sequencing of whole-body homogenates (mRNAseq) revealed a massive, transcriptome-wide response across acclimation temperatures, with a marked overrepresentation of genes that were continuously and monotonically up- and down-regulated in response to increasing acclimation temperature. Though some genes showed more complex relationships consistent with putative threshold responses, a high percentage of the differentially expressed transcriptome (42%) showed continuous and strictly monotonic relationships. Functional enrichment suggested continuous up-regulation of spermatogenesis-related transcripts with increasing temperature and continuous up-regulation of oxidative phosphorylation-related transcripts with decreasing temperature, illustrating contrasting patterns consistent with previous studies of thermal sensitivity of male reproduction and metabolic compensation in the cold. Thus, continuous thermal sensitivity of transcription is a hallmark of acclimation in D. subobscura that likely underlies the continuous thermal sensitivity of downstream physiological processes. We also provide evidence for shared transcriptomic responses across short-term acclimation (this study) vs. published results for long-term, developmental acclimation.

Color polymorphisms offer a powerful lens for examining how selection shapes genetic and phenotypic variation. Genomic analyses of color variation provide deeper insight into how genetic differences and phenotypic plasticity contribute to trait variation. Here, we use the bluefin killifish (Lucania goodei) to study this relationship. Male fins can display either red or yellow coloration based on pigments (pterins) or blue structural coloration (iridophores) often induced in UV-depauperate environments. Female fins lack pigmentation. To characterize the molecular basis of this variation, we assembled a high-quality genome and examined gene expression in the anal fins of male and female bluefin killifish to identify the molecular mechanisms underlying color variation. Our gene expression analysis found sex differences driven by male-biased upregulation of melanin synthesis and canonical pigment pathway genes. We additionally identified that the progesterone sex receptor was upregulated in females. Among male color morphs, several genes involved in xanthophore and iridophore formation differed between blue and non-blue males, including the transcription factor tfec, and iridophore-patterning genes atic, pnp4a, and sox10. Extraocular opsins, which are involved in non-image-forming light perception, were expressed at low levels across all fins, but showed population- and morph-specific patterns; notably, rgrb (retinal G protein coupled receptor b) was upregulated in blue males. To the best of our knowledge, this is the first report of an extraocular opsin varying as a function of population and color morph. Together, these results identify the pigment pathways underlying male-limited color polymorphisms and reveal candidate genes likely involved in light-sensitive phenotypic plasticity.

The sea star Patiria miniata is a widely used and powerful model organism for cell, developmental, and reproductive biology, but it has lacked genetic tools for expressing transgenes or endogenously tagging proteins. We developed a protocol to endogenously tag a broadly expressed actin gene and to express additional fluorescent markers from the same locus, using CRISPR/Cas9 genome editing. We also identified and isolated a promoter sequence of this actin gene which drives expression of transgenes. This promoter and transgene cassette can be introduced via a plasmid into the genome and persist through metamorphosis into the juvenile stage. Robust methods to induce metamorphosis that result in healthy juveniles are essential for developing stable transgenic lines and have been lacking in the field. Here we report a fast and efficient approach to induce the metamorphosis of larvae into healthy juveniles by introducing surf clam shells. Thus, we present a reliable method to generate both CRISPR/Cas9 knock-in and plasmid-integrated transgenic juvenile P. miniata, enabling future research on their fascinating biology, including regeneration, oogonial stem cells, metamorphosis, and more.

Multiple hypotheses have been formulated to explain differences in tissue repair ability across vertebrates. One hypothesis posits that the accessibility of actively cycling stromal cells within uninjured tissue confers access to a proliferative population in response to tissue damage. This hypothesis further suggests that animals with an indeterminate growth mode possess an actively cycling cell population necessary for growth that can be readily accessed for tissue regeneration. Moreover, the absence of an actively cycling population in connective tissue provides a mechanism that restricts regeneration in animals with determinate growth whose cells are refractory to cell cycle progression and proliferation to produce new tissue for morphogenesis. Here, we explore this paradigm using an EdU-BrdU pulse chase strategy in four different vertebrate species: two with determinate (Acomys dimidiatus and Mus musculus) and two with indeterminate modes of growth (Danio rerio and Ambystoma mexicanum). We find that although indeterminate growers do possess a small population of actively cycling cells, this population does not contribute to regeneration. Moreover, we found that while Acomys does not possess a population of actively cycling stromal cells, cells re-enter the cell cycle de novo in these animals to contribute to regeneration. Furthermore, testing this hypothesis allowed us to ask whether tissue injury could stimulate cell cycle re-entry - a so-called primed state - in cells at distance from the injury site in these four species and we did not find evidence of such priming in stromal or epidermal tissue. HighlightsO_LICell cycle re-entry is a common response to injury in regenerative and non-regenerative vertebrates that is independent of actively cycling stromal cells in uninjured connective tissue C_LIO_LIActively cycling cells do not contribute to regenerative healing in spiny mice, axolotls or zebrafish. C_LIO_LIOur data do not support systemic cell cycle activation in response to injury. C_LI

Exposure to the potassium channel blocker barium chloride (BaCl2) causes head degeneration in Dugesia japonica flatworms, followed by regeneration of BaCl2-insensitive heads, offering a unique model for studying transcriptional resilience to novel stress. We performed RNA sequencing on individual planaria to investigate different transcriptional solutions to the BaCl2 challenge, and how regeneration history and social environment shape transcriptomic responses to BaCl2. We identified a robust transcriptional strategy and a potential sub-strategy for enabling BaCl2-insensitive head formation. Moreover, we observed pronounced transcriptional differences between untreated worms regenerating from tail fission fragments (tail-regenerated), and untreated full-sized worms that did not fission during the experiment (intact controls), highlighting the lasting impact of regeneration history. Relative to controls, tail-regenerated worms upregulated neurodevelopmental and morphogenetic programs, while downregulating mitochondrial transport and stress-response pathways. Relative to intact controls, BaCl2-exposed regenerates upregulated ion transport, metabolic, cell cycle, and inflammatory pathways, while downregulating neuronal signaling, ion homeostasis, morphogenesis, and tissue repair programs. Comparison of BaCl2-exposed isolated and BaCl2-exposed group-housed worms revealed minimal transcriptional divergence between social conditions. These findings underscore the complex interplay between regeneration, chemical stress, and social context in shaping gene expression.

Offspring phenotypes are often influenced by maternal age at reproduction. However, the persistence of such effects across multiple generations remains poorly understood, especially in rare cases where offspring of older mothers exhibit enhanced performance. Using the predatory mite Amblyseius herbicolus, we experimentally tested whether maternal age at reproduction influences offspring life history across two generations under contrasting dietary conditions. We found that grandmaternal (F0) and maternal (F1) age affected offspring (F2) developmental time and body size, but not hatching success, survival, or oviposition. The effect of maternal age on body size depended on grandmaternal age, suggesting that grandmaternal age mediates how mothers adjust offspring provisioning. Diet strongly influenced offspring traits but showed limited interaction with age effects. To our knowledge, this is the first study to demonstrate the persistence of an inverse Lansing effect across generations, whereby enhanced immature development is maintained without detectable trade-offs in reproduction or adult survival. These results identify maternal age as a key driver of transgenerational phenotypic variation, with important implications for population dynamics and responses to environmental change at the population level.

Laboratory environments can induce rapid phenotypic changes, but the earliest responses of natural populations to laboratory conditions remain poorly understood. Using geometric morphometrics, we investigated changes in wing size and wing shape in the Neotropical drosophilid Drosophila sturtevanti. We compared field-collected males (G0) with descendants from 12 lines each established from a single female from the same native population in the first (F1) and tenth (F10) laboratory generations. Wing size showed heterogeneous responses in F1, followed by a consistent reduction by F10, possibly reflecting differences among founder females and larval density. Wing shape changed significantly in every line between G0 and F1 and between F1 and F10. Total shape variance increased significantly between G0 and F1. Within-line shape variation was not significantly lower in F1 or F10 than the variation observed in G0, while between-line variation increased as the lines diverged. These patterns are consistent with previously cryptic variation becoming expressed following environmental change, together with founder effects, drift and increasing homozygosity. Our results show that substantial morphological changes can arise within a single laboratory generation, challenging the assumption that F1 individuals provide an unaltered representation of natural populations.

The production of gametes is one of the universal processes of life and given millennia of evolution many of the core genes involved are expected to be highly refined and resistant to change. Here we examine the pattern of expression and functionally characterize three genes widely involved in gametogenesis: Vasa, Piwi, and Dnmt1. We examine their cellular location during both oogenesis and spermatogenesis in Oncopeltus fasciatus, a hemipteran insect, using fluorescent in situ hybridization chain reaction. In females, expression of Piwi was restricted to the trophocytes, but Vasa and Dnmt1 were expressed in developing ooctyes as well as the trophoctyes. In males, Piwi was expressed in the testis germline stem cells (GSCs), but Vasa and Dnmt1 expression was absent from these cells. Additionally, Piwi and Vasa were expressed in secondary spermatogonia and spermatocytes while Dnmt1 was predominantly expressed in the primary spermatogonia. We also functionally characterized their necessity for gametogenesis after RNAi-mediated gene expression knockdown. Vasa was not required for oogenesis but was required during spermatogenesis. Piwi and Dnmt1 were required for both oogenesis and spermatogenesis. These results were in contrast to their requirement for these processes from other organisms, which highlight the unexpected variation found in the processes and suggest that conservation depends on the level at which genes are examined: sequence, expression, or phenotypic and biochemical function. This suggests there is a more nuanced evolutionary story of conserved, yet plastic, gametogenic gene set in Metazoa that deserves further study across more organisms.

Research has shown that tropical corals inhabiting warmer, more thermally variable reef environments often exhibit reduced bleaching. However, the influence of diel thermal variation (DTV) is rarely tested experimentally independent of changes in mean temperature, and few studies have explored responses of coral hosts together with their associated microbial consortia (Symbiodiniaceae algae and bacteria). Here, using a common garden approach with two species of endangered reef-building corals (Orbicella franksi & O. faveolata), we show that 90 days of DTV priming (26{degrees}C {+/-} 2.4{degrees}C day-1) elicited little physiological or gene expression plasticity and did not alter Symbiodiniaceae or bacterial compositions relative to corals under stable conditions (26{degrees}C). Critically, when these corals experienced a subsequent heat challenge (32{degrees}C for 15 days), both species exhibited broad physiological and gene expression responses regardless of DTV priming. A systems biology approach linking gene expression with experimental treatments and traits supports the presence of both 1) convergent gene modules associated with homeostasis in both host species and 2) divergent gene modules showcasing enrichment of catabolism in O. faveolata and classic protein folding functions in O. franksi under thermal challenge. Together, these data highlight that while congeneric coral species exhibit divergent gene expression responses to thermal challenges, DTV priming did not facilitate thermal stress resistance. These findings suggest that other environmental parameters that co-vary with DTV on a reef may play a more influential role in bleaching mitigation.

Risk tolerance is influenced by both environmental and genetic factors and may be shaped by local selective pressures in hazardous environments. In Northern Senegal, fishermen from the village of Guet Ndar are chronically exposed to high occupational mortality risk, making this population a potential model for local adaptation to risky environments. In a previous study, we showed that men from this fishing community were less risk-tolerant than men from a nearby farming village, although this difference could not be explained by variation at the DRD4 locus. Here, we investigated whether genetic variants previously associated with general risk tolerance in large genome-wide association studies (GWAS) exhibit signals of local adaptation in these Senegalese populations. We genotyped 44 candidate SNPs in 373 individuals sampled from the risky fishing area and the non-risky farming area. Population genetic analyses revealed extremely low and non-significant differentiation between the two populations (mean FST = 0.0003, p = 0.33), indicating that the two groups are genetically indistinguishable at these loci. Furthermore, none of the candidate SNPs showed a significant association with experimentally measured risk tolerance after correction for multiple testing. These results provide no evidence that local adaptation for risky behavior has occurred, several explanations may account for this negative result.

Parental qualities can influence the development and fitness of their offspring via genetic and non-genetic effects. Although these effects are often linked to parental phenotypes, the effect of parental genetic variation linked with relevant phenotypes is less well understood. We performed full factorial crosses based on parental genotypes for an age-at-maturity-related gene, vgll3, to investigate how the parental genotypes influence Atlantic salmon (Salmo salar) offspring survival, growth, and development in their early life. Beyond the connection with age at maturity, the additional association between vgll3 and body condition in Atlantic salmon offers a potential pathway by which the maternal vgll3 genotype could influence offspring early life fitness. Combined with measurements of maternal phenotype and egg characteristics, the crossing design therefore allowed us to disentangle the maternal and paternal genetic and non-genetic contributions to variation in offspring survival and phenotypic traits. The phenotypic traits measured were hatching length and yolk sac area, growth, and yolk sac consumption and conversion efficiency. Parental vgll3 genotype did not influence the majority of our measured egg traits or alevin traits except for a genetic effect of paternal vgll3 genotype on offspring survival, whereby the paternal late maturation allele was associated with higher survival. Maternal effects were strongest for survival and for traits associated with hatching and weaker for alevin growth and yolk sac usage. Paternal effects on the measured alevin traits were negligible. The results from our study demonstrate that both maternal and paternal effects have the potential to influence offspring early life fitness traits.