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Abstract BackgroundDifferences in morphology, ecology, and behavior through ontogeny can result in opposing selective pressures at different life stages. Most animals, however, transition through two or more distinct phenotypic phases, which is hypothesized to allow each life stage to adapt more freely to its ecological niche. How this applies to sensory systems, and in particular how sensory systems adapt across life stages at the molecular level, is not well understood. Here, we used whole-eye transcriptomes to investigate differences in gene expression between tadpole and juvenile southern leopard frogs (Lithobates sphenocephalus), which rely on vision in aquatic and terrestrial light environments, respectively. Because visual physiology changes with light levels, we also tested the effect of light and dark exposure. ResultsWe found 42% of genes were differentially expressed in the eyes of tadpoles versus juveniles and 5% for light/dark exposure. Analyses targeting a curated subset of visual genes revealed significant differential expression of genes that control aspects of visual function and development, including spectral sensitivity and lens composition. Finally, microspectrophotometry of photoreceptors confirmed shifts in spectral sensitivity predicted by the expression results, consistent with adaptation to distinct light environments. ConclusionsOverall, we identified extensive expression-level differences in the eyes of tadpoles and juveniles related to observed morphological and physiological changes through metamorphosis and corresponding adaptive shifts to improve vision in the distinct aquatic and terrestrial light environments these frogs inhabit during their life cycle. More broadly, these results suggest that decoupling of gene expression can mediate the opposing selection pressures experienced by organisms with complex life cycles that inhabit different environmental conditions throughout ontogeny.
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Seasonal heterochrony of reproductive development and gene expression in a polymorphic salamander
Abstract BackgroundLife cycle evolution includes ecological transitions and shifts in the timing of somatic and reproductive development (heterochrony). However, heterochronic changes can be tissue‐specific, ultimately leading to the differential diversification of traits. Salamanders exhibit alternative life cycle polymorphisms involving either an aquatic to terrestrial metamorphosis (biphasic) or retention of aquatic larval traits into adulthood (paedomorphic). In this study, we used gene expression and histology to evaluate how life cycle evolution impacts temporal reproductive patterns in males of a polymorphic salamander. ResultsWe found that heterochrony shifts the distribution of androgen signaling in the integument, which is correlated with significant differences in seasonal reproductive gland development and pheromone gene expression. In the testes, androgen receptor (ar) expression does not significantly vary between morphs or across seasons. We found significant differences in the onset of spermatogenesis, but by peak breeding season the testes were the same with respect to both histology and gene expression. ConclusionThis study provides an example of how seasonal heterochronic shifts in tissue‐specificargene expression can disparately impact seasonal development and expression patterns across tissues, providing a potential mechanism for differential diversification of reproductive traits.
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- Award ID(s):
- 1840987
- PAR ID:
- 10581969
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Developmental Dynamics
- Volume:
- 254
- Issue:
- 4
- ISSN:
- 1058-8388
- Format(s):
- Medium: X Size: p. 330-347
- Size(s):
- p. 330-347
- Sponsoring Org:
- National Science Foundation
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