Species and population specific gene expression in blood transcriptomes of marine turtles.

BACKGROUND: Transcriptomic data has demonstrated utility to advance the study of physiological diversity and organisms' responses to environmental stressors. However, a lack of genomic resources and challenges associated with collecting high-quality RNA can limit its application for many wild populations. Minimally invasive blood sampling combined with de novo transcriptomic approaches has great potential to alleviate these barriers. Here, we advance these goals for marine turtles by generating high quality de novo blood transcriptome assemblies to characterize functional diversity and compare global transcriptional profiles between tissues, species, and foraging aggregations. RESULTS: We generated high quality blood transcriptome assemblies for hawksbill (Eretmochelys imbricata), loggerhead (Caretta caretta), green (Chelonia mydas), and leatherback (Dermochelys coriacea) turtles. The functional diversity in assembled blood transcriptomes was comparable to those from more traditionally sampled tissues. A total of 31.3% of orthogroups identified were present in all four species, representing a core set of conserved genes expressed in blood and shared across marine turtle species. We observed strong species-specific expression of these genes, as well as distinct transcriptomic profiles between green turtle foraging aggregations that inhabit areas of greater or lesser anthropogenic disturbance. CONCLUSIONS: Obtaining global gene expression data through non-lethal, minimally invasive sampling can greatly expand the applications of RNA-sequencing in protected long-lived species such as marine turtles. The distinct differences in gene expression signatures between species and foraging aggregations provide insight into the functional genomics underlying the diversity in this ancient vertebrate lineage. The transcriptomic resources generated here can be used in further studies examining the evolutionary ecology and anthropogenic impacts on marine turtles.

Trace Element Concentrations in Blood and Scute Tissues from Wild and Captive Hawaiian Green Sea Turtles (Chelonia mydas).

Sea turtles are exposed to trace elements through water, sediment, and food. Exposure to these elements has been shown to decrease immune function, impair growth, and decrease reproductive output in wildlife. The present study compares trace element concentrations in green turtles in captivity at Sea Life Park Hawaii (n = 6) to wild green turtles in Kapoho Bay, Hawaii, USA (n = 5-7). Blood and scute samples were collected and analyzed for 11 elements via inductively coupled plasma-mass spectrometry (ICP-MS). Selenium was significantly greater (p < 0.05) in the blood of captive turtles compared with wild turtles, whereas V, Ni, and Pb were significantly greater in the blood of wild turtles. In scute, V, Cu, Se, and Cr were significantly greater in captive turtles, whereas As was significantly greater in wild turtles. Pelleted food fed to the captive turtles and representative samples of the wild turtle diet were analyzed via ICP-MS to calculate trophic transfer factors and daily intake values. Wild turtles had greater estimated daily intake than captive turtles for all elements except Cu and Se. Because captive turtles are fed a diet very different from that of their wild counterparts, captive turtles do not represent control or reference samples for chemical exposure studies in wild turtles. No toxic thresholds are known for sea turtles, but rehabilitation and managed care facilities should monitor sea turtle elemental concentrations to ensure the animals' health. Environ Toxicol Chem 2021;40:208-218. © 2020 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.