Abstract
Simple SummaryGreen sea turtles are an endangered species prone to a disease called fibropapillomatosis (FP). FP causes the growth of large debilitating tumors on the skin, eyes, and shell of sea turtles. Sea turtle rehabilitation facilities often treat turtles with this disease by removing the tumors, but many of these individuals do not survive or the tumors regrow. A way to improve the treatment of these turtles could help the population as a whole. The aim of this study was to compare plasma vitamin D levels in green sea turtles with and without evident FP tumors, as vitamin D influences immune function and overall health. We determined that exposure to more sunlight influences plasma vitamin D levels in sea turtles brought into a rehabilitation facility. We found that tumored individuals arriving at the facility had lower vitamin D and ionized calcium levels and higher parathyroid hormone levels compared to both wild-caught and rehabilitation turtles without evident tumors. Individuals housed in tanks exposed to greater ultraviolet (UV) (sun)light showed greater increases in plasma vitamin D levels and a more successful recovery. The results suggest that increasing sun exposure in rehabilitation facilities may enhance health and recovery in green turtles with FP. Green sea turtles (Chelonia mydas) are an endangered species, which as juveniles are prone to the debilitating disease green turtle fibropapillomatosis (FP). Previous work has shown an association between reduced immune function and FP. As vitamin D has been linked to immune function in numerous animals, the aim of this study was to compare vitamin D levels in green sea turtles with and without evident FP and determine if exposure to sunlight would influence vitamin D levels and other health parameters. Various health markers, including vitamin D, in turtles with and without evident tumors being treated at a rehabilitation facility in southeast Florida were compared to apparently healthy wild-caught juvenile green turtles. Turtles receiving treatment were housed in tanks exposed to higher or lower levels of sunlight for up to 6 months. Upon intake, tumored individuals had lower plasma vitamin D and ionized calcium levels and higher parathyroid hormone levels when compared to both wild-caught and rehabilitation turtles without evident tumors. Individuals exposed to greater sunlight showed greater increases in plasma vitamin D and a more successful recovery. The results suggest that increasing sun exposure in rehabilitation facilities may enhance health and recovery in green turtles with FP.
Highlights
Green turtle fibropapillomatosis (FP) is a debilitating disease that affects sea turtles worldwide
We compared vitamin D levels and blood chemistry values in turtles without evident FP tumors vs turtles with evident tumors kept in varying UV light conditions at the rehabilitation facility at Gumbo Limbo Nature Center (GLNC)
The turtles used in this study were divided into three main groups: turtles at GLNC for rehabilitation with evident tumors (VT+), turtles at GLNC for rehabilitation without evident tumors (VT−), and healthy turtles caught by IRG, without evident tumors
Summary
Green turtle fibropapillomatosis (FP) is a debilitating disease that affects sea turtles worldwide. It primarily affects juvenile green sea turtles (Chelonia mydas), it has been confirmed in all species of hard-shelled marine turtles [1,2,3,4,5,6]. The expression of the disease is prevalent in polluted environments [11,12,13,14], and FP has been associated with a suppressed immune system as either a causal or resultant effect [15,16,17,18,19]. Finding a way to improve the health of animals being treated for FP may result in better outcomes; increasing vitamin D levels could be one way of doing so
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