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ABSTRACT Animal coloration is a complex phenotype that may be affected by genetics, evolution, ecology, and environment. Disentangling the impact of environment on phenotype can often be done in laboratory studies, but the results do not necessarily correspond to the natural variation present in the wild. Painted turtles are a brightly colored freshwater species that inhabit a variety of environments in North America. There is known to be plasticity in the melanin coloration of the shell of painted turtles in a lab setting, but this has not been measured in the wild. The bright skin coloration that gives painted turtles their name is caused by carotenoids, which can only be obtained from an organism's diet in vertebrates. Though the availability of carotenoids likely varies between environments, and there is evidence that some of the carotenoid‐based coloration in this species is a visual signal, it is unknown if or how environmental variation impacts coloration in the wild. To address this, we measured the effect of the environment on turtle coloration by assessing multiple populations of painted turtles in northern Wisconsin. We measured water clarity and aquatic plant density at each site where turtles were caught. We found that females had brighter carapaces than males, and that plastron brightness varied with water clarity and plant density, despite its ventral orientation. We also found that neither water clarity nor plant density predicted carotenoid chroma, despite reason to believe that light environment and carotenoid availability should impact a visual signal. These findings suggest that colorful phenotypic traits in this turtle species are complex and their potential role as visual signals requires more research. It is crucial to understand the different phenotypes of painted turtles since coloration may influence fitness in this species, and since laboratory studies are unable to represent natural variation.
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Establishment and characterization of turtle liver organoids provides a potential model to decode their unique adaptations
Abstract: Painted turtles are remarkable for their freeze tolerance and supercooling ability along with their associated resilience to hypoxia/anoxia and oxidative stress, rendering them an ideal biomedical model for hypoxia-induced injuries (including strokes), tissue cooling during surgeries, and organ cryopreservation. Yet, such research is hindered by their seasonal reproduction and slow maturation. Here we developed and characterized adult stem cell-derived turtle liver organoids (3D self-assembled in vitro structures) from painted, snapping, and spiny softshell turtles spanning ~175My of evolution, with a subset cryopreserved. This development is, to the best of our knowledge, a first for this vertebrate Order, and complements the only other non-avian reptile organoids from snake venom glands. Preliminary characterization, including morphological, transcriptomic, and proteomic analyses, revealed organoids enriched in cholangiocytes. Deriving organoids from distant turtles and life stages demonstrates that our techniques are broadly applicable to chelonians, permitting the development of functional genomic tools currently lacking in herpetological research. Such platform could potentially support studies including genome-to-phenome mapping, gene function, genome architecture, and adaptive responses to climate change, with implications for ecological, evolutionary, and biomedical research.
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- Award ID(s):
- 2127995
- PAR ID:
- 10509018
- Publisher / Repository:
- Communications Biology
- Date Published:
- Journal Name:
- Communications Biology
- Volume:
- 7
- Issue:
- 1
- ISSN:
- 2399-3642
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract BackgroundEnvironmental fluctuation during embryonic and fetal development can permanently alter an organism’s morphology, physiology, and behaviour. This phenomenon, known as developmental plasticity, is particularly relevant to reptiles that develop in subterranean nests with variable oxygen tensions. Previous work has shown hypoxia permanently alters the cardiovascular system of snapping turtles and may improve cardiac anoxia tolerance later in life. The mechanisms driving this process are unknown but may involve epigenetic regulation of gene expression via DNA methylation. To test this hypothesis, we assessed in situ cardiac performance during 2 h of acute anoxia in juvenile turtles previously exposed to normoxia (21% oxygen) or hypoxia (10% oxygen) during embryogenesis. Next, we analysed DNA methylation and gene expression patterns in turtles from the same cohorts using whole genome bisulfite sequencing, which represents the first high-resolution investigation of DNA methylation patterns in any reptilian species. ResultsGenome-wide correlations between CpG and CpG island methylation and gene expression patterns in the snapping turtle were consistent with patterns observed in mammals. As hypothesized, developmental hypoxia increased juvenile turtle cardiac anoxia tolerance and programmed DNA methylation and gene expression patterns. Programmed differences in expression of genes such asSCN5Amay account for differences in heart rate, while genes such asTNNT2andTPM3may underlie differences in calcium sensitivity and contractility of cardiomyocytes and cardiac inotropy. Finally, we identified putative transcription factor-binding sites in promoters and in differentially methylated CpG islands that suggest a model linking programming of DNA methylation during embryogenesis to differential gene expression and cardiovascular physiology later in life. Binding sites for hypoxia inducible factors (HIF1A, ARNT, and EPAS1) and key transcription factors activated by MAPK and BMP signaling (RREB1 and SMAD4) are implicated. ConclusionsOur data strongly suggests that DNA methylation plays a conserved role in the regulation of gene expression in reptiles. We also show that embryonic hypoxia programs DNA methylation and gene expression patterns and that these changes are associated with enhanced cardiac anoxia tolerance later in life. Programming of cardiac anoxia tolerance has major ecological implications for snapping turtles, because these animals regularly exploit anoxic environments throughout their lifespan.more » « less
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Temperature-dependent sex determination (TSD) decides the sex fate of an individual based on incubation temperature. However, other environmental factors, such as pollutants, could derail TSD sexual development. Cadmium is one such contaminant of soils and water bodies known to affect DNA methylation, an epigenetic DNA modification with a key role in sexual development of TSD vertebrate embryos. Yet, whether cadmium alters DNA methylation of genes underlying gonadal formation in turtles remains unknown. Here, we investigated the effects of cadmium on the expression of two gene regulators of TSD in the painted turtle, Chrysemys picta, incubated at male-producing and female-producing temperatures using qPCR. Results revealed that cadmium alters transcription of Dmrt1 and aromatase, overriding the normal thermal effects during embryogenesis, which could potentially disrupt the sexual development of TSD turtles. Results from a preliminary DNA methylation-sensitive PCR assay implicate changes in DNA methylation of Dmrt1 as a potential cause that requires further testing (aromatase methylation assays were precluded).more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s42003-024-05818-1
