Study at molecular level finds Indian River Lagoon green sea turtles biologically stressed
Compromised immune function in Indian River lagoon's green sea turtles
makes them more vulnerable to tumors

Date:
October 12, 2021
Source:
Florida Atlantic University
Summary:
Turtles from the heavily polluted Indian River Lagoon
(IRL) had compromised immune function. Those with tumors
(Green Turtle Fibropapillomatosis or GTF) had less immune
competence. Habitat quality, disease state, and immune function
are intertwined. Polluted environments impact the immune system
and make animals more prone to the expression of GTF, which in
turn further compromises the immune system. This vicious cycle may
explain why some areas have such a high incidence of GTF, while
other areas have turtles that test positive for the GTF virus,
but are clinically healthy.



FULL STORY ========================================================================== Juvenile green sea turtles (Chelonian mydas) living in nearshore
waters often exhibit tumors that grow on their soft tissues and shells, symptoms of a disease called Green Turtle Fibropapillomatosis. While the disease has been linked to a virus called chelonid alpha-herpesvirus 5,
the virus has co-existed within turtle populations for more than 300
million years, although the disease itself has become pandemic only in
the last century. The virus can be found in clinically healthy turtles
that don't have any tumors, suggesting that expression of the disease
is multi-factorial. Evidence from other studies shows that there is a
link between environmental pollution and immune suppression in a variety
of animals.


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

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

Results of the study, published in the Journal of Wildlife Diseases,showed
that both adaptive and innate immune function were compromised in green
sea turtles captured in the Indian River Lagoon, where historical rates
of Green Turtle Fibropapillomatosis in that population are greater than
50 percent. Within the Indian River Lagoon, turtles that expressed
tumors had less immune competence that those in that habitat without
tumors. By comparison, turtles from the Trident Basin are free of Green
Turtle Fibropapillomatosis, and both their innate and adaptive branches
of immune function exhibited greater immune competence.

"Findings from our study suggest that habitat quality, disease state,
and immune function are intertwined, forming a positive feedback loop
wherein polluted environments impact the immune system and make animals
more prone to the expression of Green Turtle Fibropapillomatosis, which in
turn further compromises the immune system," said Sarah L. Milton, Ph.D.,
lead author and chair and professor, Department of Biological Sciences,
Charles E. Schmidt College of Science. "Reduced immune competence may
initially permit disease, and disease status in turn may then further
hinder immune-competence. Such a vicious cycle could explain why certain locations have such a high incidence of disease, while other areas
have turtles that test positive for chelonid alphaherpesvirus 5 but are clinically healthy." An earlier study by Milton of stress responses at
the molecular level also suggested that green sea turtles in the Indian
River Lagoon are physiologically stressed. Whether they had visible
tumors or not, levels of cellular stress markers were higher in these
animals than in the Trident Basin turtles.

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

The green seas turtles were sampled in 1999 and 2001 and from 2011 to
2013 across all seasons. As part of ongoing tag-recapture studies in the
Indian River Lagoon and Trident Basin, this study was conducted under
permit from Florida Fish and Wildlife Conservation Commission (permit
No. FWC MTP186, permit No. FWC MTP053) and National Marine Fisheries
Service (permit No. NMFS 14506).

========================================================================== Story Source: Materials provided by Florida_Atlantic_University. Original written by Gisele Galoustian. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Patricia Sposato, Patricia Keating, Peter L. Lutz, Sarah L. Milton.

EVALUATION OF IMMUNE FUNCTION IN TWO POPULATIONS OF GREEN SEA
TURTLES (CHELONIA MYDAS) IN A DEGRADED VERSUS A NONDEGRADED
HABITAT. Journal of Wildlife Diseases, 2021; 57 (4) DOI:
10.7589/JWD-D-20-00204 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211012112254.htm

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