Indian River Lagoon Green Sea Turtles’ compromised immune function makes them more susceptible to tumors – sciencedaily


Juvenile green turtles (chelonian mydas) living in nearshore waters often have tumors that develop on their soft tissues and shells, symptoms of a disease called green turtle fibropapillomatosis. Although the disease is linked to a virus called chelonid alpha-herpesvirus 5, the virus has coexisted in turtle populations for more than 300 million years, although the disease itself did not become pandemic until the last decade or so. last century. The virus can be found in clinically healthy turtles that do not have tumors, suggesting that disease expression is multifactorial. Evidence from other studies shows that there is a link between environmental pollution and immune suppression in a variety of animals.

Researchers from the Charles E. Schmidt College of Science at Florida Atlantic University examined the immune function of two populations of non-captive green sea turtles, comparing turtles resident in an area of ​​poor water quality with those in a more pristine environment.

Researchers obtained blood samples from 87 green turtles captured and released in the Indian River Lagoon, a heavily polluted estuary with high levels of heavy metals, persistent organic pollutants and excessive nutrients, and the pristine Trident Basin and artificial moAdre, located near Cape Canaveral. . They looked at two branches of the immune system: highly specific adaptive immunity, which involves the recognition of antigens and the development of memory cells and is most often measured by the activity with which white blood cells respond to an immune challenge ( lymphocyte proliferation); and innate immunity, which acts as an initial defense mechanism against pathogens and partly involves phagocytic white blood cells that engulf foreign particles.

The results of the study, published in the Journal of Wildlife Diseases, showed that adaptive and innate immune functions were compromised in green sea turtles captured in the Indian River Lagoon, where historical rates of green turtle fibropapillomatosis in this population are greater than 50 percent. In the Indian River Lagoon, turtles that expressed tumors had less immune competence than those in this tumor-free habitat. By comparison, the Trident Basin turtles are free from green turtle fibropapillomatosis, and both their innate and adaptive branches of immune function have shown greater immune competence.

“The results of our study suggest that habitat quality, disease status, and immune function are closely related, forming a positive feedback loop in which polluted environments impact the immune system and make animals more prone to green turtle fibropapillomatosis expression, which in turn further compromises the immune system, ”said Sarah L. Milton, Ph.D., senior author and chair and professor, Department of Biological Sciences , Charles E. Schmidt College of Science. “Reduced immune competence may initially allow disease, and the disease state in turn may then further hamper immune competence. Such a vicious cycle could explain why some places have such a high incidence of disease, while others have turtles that tested positive for alphaherpes chelonide. 5 but are clinically healthy. “

An earlier study by Milton of stress responses at the molecular level also suggested that Indian River Lagoon green sea turtles are physiologically stressed. Whether or not they had visible tumors, the levels of cellular stress markers were higher in these animals than in the turtles of the Trident Basin.

Study co-authors are Patricia Sposato, from the Department of Biological Sciences at FAU and the Walkabout Ecological Team, Inc .; Patricia Keating, Ph.D., post-doctoral researcher, Department of Biological Sciences, FAU; and Peter L. Lutz, Ph.D., (deceased), Department of Biological Sciences, FAU.

Green sea turtles were sampled in 1999 and 2001 and from 2011 to 2013 across all seasons. As part of the ongoing tag recapture studies in the Indian River Lagoon and Trident Basin, this study was conducted with a permit from the Florida Fish and Wildlife Conservation Commission (permit no. FWC MTP186, permit no. ° FWC MTP053) and the National Marine Fisheries Service (license N ° NMFS 14506).

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Materials provided by Atlantic University of Florida. Original written by Gisèle Galoustian. Note: Content can be changed for style and length.