Biology subjects

Strader, M. E.

Publications and source records attributed to Strader, M. E..

6 recordsLinked to original sources

bioRxiv2026

Seasonal temperature extremes drive shifts in reproductive strategy in Cassiopea xamachana

Large observable densities of jellyfish (Scyphozoa) can seemingly appear out of nowhere but can often be explained by life-history transitions triggered by temperature and host associations with microorganisms. Using a globally distributed scyphozoan, we demonstrate that seasonal temperature extremes trigger polyps to differentially allocate effort in growth and reproductive output and strategy mostly independent of their microbiomes. Cassiopea xamachana polyps were reared under winter (20{degrees}C), ambient (28{degrees}C), and summer (33{degrees}C) temperatures with either antibiotic-treated (ABS) or microbe-exposed (MES) communities. At 20{degrees}C, polyps grew and reproduced through budding but did not strobilate. At 28{degrees}C, polyps sustained the greatest ephyra production, whereas 33{degrees}C accelerated first ephyra release but subsequently truncated strobilation and yielded smaller ephyrae with poorer condition and survival. These patterns indicate that plasticity induced by seasonal temperature extremes may optimize differential allocation towards asexual and sexual propagation. Microbial depletion restructured polyp-associated communities, yet only minimally altered growth and reproduction. Taken together, C. xamachana polyps are likely to overwinter, where they maximize growth and asexual reproduction. As temperatures warm, it triggers a shift in resource allocation towards strobilation. However, the warmest summer temperatures reduced polyp and ephyra fitness, with the magnitude of effect modified by their microbiome.

physiology↗

bioRxiv2026

Environmental microbial communities and host selection shape larval microbiomes

Ocean warming is altering abiotic environments and biotic interactions experienced by marine organisms, where sensitive early developmental windows occur in biologically complex seawater communities. The impact of these interactions on developmental processes and fitness in hosts is not well understood, but likely contingent on the establishment of a host-associated microbiome. Here, we hypothesize that temperature and microbial exposure during embryogenesis influence larval microbiome assembly and host morphology. Strongylocentrotus purpuratus embryos were raised in low microbial richness (LMR) or high microbial richness (HMR) seawater at ambient (14 {degrees}C) or elevated (18 {degrees}C) temperature, then collected at 2, 4, and 6 days post-fertilization (dpf) following multiple feedings. Higher microbial diversity was observed in larvae that developed in HMR seawater when compared to LMR. Differences in relative abundances of dominant microbial families between seawater and larvae suggest some degree of host selectivity in microbiome assembly. Temperature did not strongly alter microbiome composition, but both temperature and microbial condition led to differences in larval morphology by 6 dpf, potentially due to enrichment of microbes with chemoheterotrophic functions. By linking how temperature and microbial communities interact with host development, we contribute novel insights into how early-life environmental conditions impact holobiont formation and morphology. One sentence summaryEarly developmental temperature and microbial conditions shape larval microbiome establishment and morphology.

ecology↗

bioRxiv2024

Transgenerational effects alter the fitness consequences and genetic architecture of phenotypic plasticity and its regulatory pathways

Transgenerational effects, where parental environments influence offspring phenotype, facilitate acclimation over ecological timescales. Transgenerational effects may also influence evolution by altering the fitness costs of offspring traits and the expression of genetic variation. We tested the evolutionary role of transgenerational effects in the sea urchin Strongylocentrotus purpuratus, whose populations are exposed to coastal upwelling (periods of low temperature and pH) and exhibit local adaptation, parental effects, and phenotypic plasticity in response to upwelling. Using a quantitative genetic breeding design, we conditioned parents and larvae to upwelling or control conditions and combined RNA-seq with larval phenotyping (body size, biomineralization, survival). Larval upwelling exposure caused widespread differential expression (DE), reduced biomineralization, and reduced size. Survival was linked to biomineralization, body size, and their plasticity under upwelling, but only in offspring of upwelling-conditioned parents -evidence that parental environment affected selection on offspring traits. DE under upwelling was associated with adaptive plasticity in biomineralization and size, but adaptive gene expression changes shared negative genetic correlations. However, genetic correlations in gene expression associated with body size plasticity were significantly more positive in larvae from upwelling parents. Parental conditioning strengthened selection on offspring performance and reduced genetic tradeoffs between performance-associated expression pathways, potentially accelerating adaptation.

evolutionary biology↗

bioRxiv2024

Temperature influences immune cell development and body length in purple sea urchin larvae

Anthropogenic climate change has increased the frequency and intensity of marine heatwaves that may broadly impact the health of marine invertebrates. Rising ocean temperatures lead to increases in disease prevalence in marine organisms; it is therefore critical to understand how marine heatwaves impact immune system development. The purple sea urchin (Strongylocentrotus purpuratus) is an ecologically important, broadcast-spawning, omnivore that primarily inhabits kelp forests in the northeastern Pacific Ocean. The S. purputatus lifecycle includes a relatively long-lived ([~]2 months) planktotrophic larval stage. Larvae have a well-characterized cellular immune system that is mediated, in part, by a subset of mesenchymal cells known as pigment cells. To assess the role of environmental temperature on the development of larval immune cells, embryos were generated from adult sea urchins conditioned at 14 {degrees}C. Embryos were then cultured in either ambient (14 {degrees}C) or elevated (18 {degrees}C) seawater. Results indicate find that larvae raised in an elevated temperature were slightly larger and had more pigment cells than those raised at ambient temperature. Further, the larval phenotypes varied significantly among genetic crosses, which highlights the importance of genotype in structuring how the immune system develops in the context of the environment. Overall, these results suggest that developmental temperature shapes the larval immune system and may adversely affect survival long-term.

ecology↗

bioRxiv2024

Blue appendages and temperature acclimation increase survival during acute heat stress in the upside-down jellyfish, Cassiopea xamachana

Upside-down jellyfish (Cassiopea sp.) are highly tolerant to multiple abiotic stressors, including fluctuating temperatures associated with shallow marine habitats. This resilience may underlie the ability of Cassiopea sp. to inhabit a wide variety of tropical habitats across the globe. Additionally, Cassiopea sp. are marked by a conspicuous array of appendage coloration; individual medusae vary in the hue and number of oral appendages, which are often strikingly blue. The function of this coloration is not understood. We aimed to understand how extrinsic and intrinsic factors may shape thermal tolerance. Adult Cassiopea xamachana were collected from two sites that vary in daily temperature range within the Florida Keys and were subjected to acute lethal heat stress experiments. To quantify a whole-organism response to heat, we measured changes in bell pulsation, which likely plays a role in feeding, oxygen exchange, and symbiont uptake. Results show that C. xamachana from the two collection sites do not exhibit different responses to heat, suggesting that temperature fluctuations do not prime individuals for higher thermal tolerance. Additionally, C. xamachana with blue appendages survived significantly higher temperatures and exhibited less change in bell pulsation rates compared to non-blue individuals. Finally, color morphs were acclimated at either ambient (26 {degrees}C) or elevated (33 {degrees}C) temperatures. We found that acclimation at 33 {degrees}C, as well as appendage color in each treatment, led to higher survival under acute heat stress. Together, these findings highlight the importance of phenotypic plasticity and coloration in Cassiopea resilience during heat stress.

ecology↗

bioRxiv2021

Gene regulation by DNA methylation is contingent on chromatin accessibility during transgenerational plasticity in the purple sea urchin

Epigenetic processes are proposed to contribute to phenotypic plasticity. In invertebrates, DNA methylation commonly varies across environments and can correlate or causally associate with phenotype, but its role in transcriptional responses to the environment remains unclear. Maternal environments experienced by the sea urchin Strongylocentrotus purpuratus induce 3 - 6x greater differential CpG methylation in offspring larvae relative to larval developmental environments, suggesting a role for DNA methylation in transgenerational plasticity (TGP). However, a negligible association has been observed between differentially methylated and differentially expressed genes. What gene regulatory roles does invertebrate DNA methylation possess under environmental change, if any? We quantified DNA methylation and gene expression in S. purpuratus larvae exposed to different ecologically relevant conditions during gametogenesis (maternal conditioning) or embryogenesis (developmental conditioning). We modeled differential gene expression and differential splicing under maternal conditioning as functions of DNA methylation, incorporating variables for genomic feature and chromatin accessibility. We detected significant interactions between differential methylation, chromatin accessibility, and genic architecture associated with differential expression and splicing. Observed transcriptional responses to maternal conditioning were also 4 - 13x more likely when accounting for interactions between methylation and chromatin accessibility. Our results provide evidence that DNA methylation possesses multiple functional roles during TGP in S. purpuratus, but its effects are contingent upon other genomic and epigenomic states. Singularly unpredictive of transcription, DNA methylation is likely one cog in the epigenomic machinery contributing to environmental responses and phenotypic plasticity in S. purpuratus and other invertebrates.

genomics↗