Sex, seasonal, and stress-related variations in elasmobranch corticosterone concentrations

Serum corticosterone was previously studied in numerous elasmobranch fishes (sharks, skates and rays), but the role of this steroid, widespread throughout many taxa, has yet to be defined. The goal of this study was to test whether corticosterone varied in response to acute and chronic capture stress, and across the reproductive cycle in the bonnethead shark, Sphyrna tiburo, and Atlantic stingray, Dasyatis sabina. Serum corticosterone in S. tiburo increased following capture and again 24 h post-capture, possibly caused by interference with 1α-hydroxycorticosterone, the primary stress hormone in elasmobranchs. Higher serum concentrations in males compared to females were observed in both species. Variations in corticosterone also occurred during the reproductive cycle in both species. Consistent with other taxa, elevations in male bonnethead sharks and stingrays coincided with peak testicular development and mating. Elevations in female bonnethead sharks occurred from the time of mating through sperm storage into early gestation. In contrast, corticosterone levels in female stingrays were low during their protracted mating season, but elevated through late gestation and parturition. These results indicate that corticosterone has a limited role, if any, in acute and chronic stress associated with capture in S. tiburo, but likely has physiological functions associated with its glucocorticoid properties across the reproductive cycle of both species. © 2007 Elsevier Inc. All rights reserved

Plasma proteomics of green turtles (\u3cem\u3eChelonia mydas\u3c/em\u3e) reveals pathway shifts and potential biomarker candidates associated with health and disease

Evaluating sea turtle health can be challenging due to an incomplete understanding of pathophysiologic responses in these species. Proteome characterization of clinical plasma samples can provide insights into disease progression and prospective biomarker targets. A TMT-10-plex-LC–MS/MS platform was used to characterize the plasma proteome of five, juvenile, green turtles (Chelonia mydas) and compare qualitative and quantitative protein changes during moribund and recovered states. The 10 plasma samples yielded a total of 670 unique proteins. Using ≥1.2-fold change in protein abundance as a benchmark for physiologic upregulation or downregulation, 233 (34.8%) were differentially regulated in at least one turtle between moribund and recovered states. Forty-six proteins (6.9%) were differentially regulated in all five turtles with two proteins (0.3%) demonstrating a statistically significant change. A principle component analysis showed protein abundance loosely clustered between moribund samples or recovered samples and for turtles that presented with trauma (n = 3) or as intestinal floaters (n = 2). Gene Ontology terms demonstrated that moribund samples were represented by a higher number of proteins associated with blood coagulation, adaptive immune responses and acute phase response, while recovered turtle samples included a relatively higher number of proteins associated with metabolic processes and response to nutrients. Abundance levels of 48 proteins (7.2%) in moribund samples significantly correlated with total protein, albumin and/or globulin levels quantified by biochemical analysis. Differentially regulated proteins identified with immunologic and physiologic functions are discussed for their possible role in the green turtle pathophysiologic response and for their potential use as diagnostic biomarkers. These findings enhance our ability to interpret sea turtle health and further progress conservation, research and rehabilitation programs for these ecologically important species

Evaluation of Serum for Pathophysiological Effects of Prolonged Low Salinity Water Exposure in Displaced Bottlenose Dolphins (Tursiops truncatus)

We conducted a retrospective study of serum biochemistry and hematologic findings from displaced, out-of-habitat bottlenose dolphins (Tursiops truncatus) exposed to various low salinity environments in waters along the southern United States including southeastern Atlantic and northern Gulf of Mexico. Serum sodium, chloride, and calculated osmolality were significantly lower and below reference ranges in displaced animals compared to free-ranging case control animals. This suggests clinical hyponatremia, hypochloremia, and hypo-osmolality due to an uptake of low saline water from the environment. In addition, significant differences were found in other serum chemistry variables, although none were outside of normal reference ranges for non-controlled free-ranging animals. Multiple linear regressions demonstrated the degree of salinity had a greater pathophysiologic response than the duration of fresh water exposure. The Na/Cl ratio and bicarbonate were the only variables that were significantly modulated by exposure duration. These findings suggest that the degree of salinity is a critical factor when assessing and managing care for dolphins chronically exposed to low salinity water. Results from this study indicate that changes in various biochemical parameters can be used to determine fresh water exposure and aid in determining the treatment for animals recovered from low salinity waters

Cultivating epizoic diatoms provides insights into the evolution and ecology of both epibionts and hosts

11 pages, 3 figures, 1 table, supplementary information https://doi.org/10.1038/s41598-022-19064-0.-- Data availability: DNA sequence data generated for this study are published on the NCBI GenBank online sequence depository under the accession numbers listed in Table S1. Additional micrographs and cleaned voucher material from the sequenced cultures are available from lead author MPAOur understanding of the importance of microbiomes on large aquatic animals—such as whales, sea turtles and manatees—has advanced considerably in recent years. The latest observations indicate that epibiotic diatom communities constitute diverse, polyphyletic, and compositionally stable assemblages that include both putatively obligate epizoic and generalist species. Here, we outline a successful approach to culture putatively obligate epizoic diatoms without their hosts. That some taxa can be cultured independently from their epizoic habitat raises several questions about the nature of the interaction between these animals and their epibionts. This insight allows us to propose further applications and research avenues in this growing area of study. Analyzing the DNA sequences of these cultured strains, we found that several unique diatom taxa have evolved independently to occupy epibiotic habitats. We created a library of reference sequence data for use in metabarcoding surveys of sea turtle and manatee microbiomes that will further facilitate the use of environmental DNA for studying host specificity in epizoic diatoms and the utility of diatoms as indicators of host ecology and health. We encourage the interdisciplinary community working with marine megafauna to consider including diatom sampling and diatom analysis into their routine practicesFinancial support for sequencing and SEM comes from the Jane and the Roland Blumberg Centennial Professorship in Molecular Evolution at UT Austin and the US Department of Defense (grant number W911NF-17-2-0091). Sampling in South Africa was done with partial financial support from The Systematics Association (UK) through the Systematics Research Fund Award granted to RM (2017 and 2020). Work in the Adriatic Sea was supported by Croatian Science Foundation, project UIP-05-2017-5635 (TurtleBIOME). KF has been fully supported by the “Young researchers' career development project – training of doctoral students” of the CSF funded by the EU from the European Social Fund. NJR was funded by the Spanish government (AEI) through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe

Evaluation of the use of metallothionein as a biomarker for detecting physiological responses to mercury exposure in the bonnethead, Sphyrna tiburo

Previous studies have demonstrated that sharks, perhaps more so than any other fishes, are capable of bioaccumulating the non-essential toxic metal mercury (Hg) to levels that threaten the health of human seafood consumers. However, few studies have explored the potential effects of Hg accumulation in sharks themselves. Therefore, the goal of this study was to examine if physiological effects occur in sharks in response to environmentally relevant levels of Hg exposure. To address this goal, the relationship between muscle Hg concentrations and muscle/hepatic levels of metallothionein (MT), a widely used protein biomarker of toxic metal exposure in fish, was examined in bonnetheads, Sphyrna tiburo, from three Florida estuaries. Total Hg concentrations in bonnethead muscle, as determined using thermal decomposition and atomic absorption spectrometry, ranged from 0.22 to 1.78 μg/g wet weight and were correlated with animal size. These observations were consistent with earlier studies on Florida bonnetheads, illustrating that they experience bioaccumulation of Hg, often to levels that threaten the health of these animals or consumers of their meat. However, despite this, MT concentrations measured using Western blot analysis were not correlated with muscle Hg concentrations. These results suggest that either environmentally relevant levels of Hg exposure and uptake are below the physiological threshold for inducing effects in sharks or MT is a poor biomarker of Hg exposure in these fishes. Of these two explanations, the latter is favored based on a growing body of evidence that questions the use of MTs as specific indicators of Hg exposure and effects in fish. © 2014 Springer Science+Business Media Dordrecht

Disseminated Mycotic Infection Caused by Colletotrichum acutatum in a Kemp's Ridley Sea Turtle (Lepidochelys kempi)

Colletotrichum acutatum is a cosmopolitan plant pathogen with a wide host range. While the organism's phytopathogenic potential has been well documented, it has never been reported as an etiologic agent of disease in either animals or humans. In this case, a juvenile Kemp's ridley sea turtle, Lepidochelys kempi, probably with immune compromise following cold stunning (extended hypothermia), developed a disseminated mycotic infection in the lungs and kidneys. Prophylactic treatment with oral itraconazole did not prevent or cure the infection. This report of a Colletotrichum acutatum infection in an animal extends the range of disease caused by this organism beyond that of a phytopathogen