# Pathology of Free-Living Loggerhead Turtle (Caretta caretta) Embryos on the Island of Linosa (Italy)

## TL;DR

This study investigates the causes of death in unhatched loggerhead turtle embryos on Linosa Island, finding liver and kidney damage likely caused by high temperatures and environmental toxins.

## Contribution

The study identifies renal calcium oxalate deposition in turtle embryos as a novel finding linked to rising temperatures and environmental stressors.

## Key findings

- 100% of unhatched embryos showed liver vacuolar degeneration and increased melanomacrophages.
- 58.1% of kidneys exhibited calcium oxalate deposition, confirmed by multiple staining techniques and TEM.
- High summer temperatures were statistically linked to the occurrence of renal oxalosis in embryos.

## Abstract

The loggerhead turtle (Caretta caretta) is a pelagic species found in all temperate oceans, including the Mediterranean Sea. In Italy, the main nesting areas are located on the islands of Linosa and Lampedusa. Despite conservation efforts, the Mediterranean subpopulation of Caretta caretta is classified as vulnerable. The main threats to the species are bycatch in fishing, habitat degradation, and climate change. In particular, the rise in environmental temperatures negatively impacts egg incubation and development. This study examined the factors contributing to mortality in unhatched embryos on Pozzolana di Ponente beach, Linosa, with a focus on renal alterations. The results showed signs of liver and kidney damage, likely due to environmental toxins and high temperatures. Global warming is increasing the sand temperature, compromising hatching success and contributing to issues like renal calcium oxalate deposition (renal oxalosys) in embryos. Conservation actions should include protecting the nests and studying the impacts of environmental contaminants to safeguard endangered sea turtles in the Mediterranean.

On the beach of Linosa Island (Italy), 43 loggerhead sea turtle (Caretta caretta) unhatched eggs were recovered from nests, formalin-fixed and necropsied. The tissue samples were stained with hematoxylin-eosin (HE), Grocott, von Kossa, periodic acid-Schiff (PAS), and Movat pentachrome stains. Histologically, vacuolar degeneration (100.0%) and increased numbers of melanomacrophages (18.6%) in the liver, and edema (14.0%) in the lungs were observed. Twenty-five kidneys (58.1%) showed deposition of blue amorphous material with HE staining, which also appeared PAS-positive and black with von Kossa staining, allowing a diagnosis of calcium oxalate, confirmed by transmission electron microscopy (TEM). The hepatic lesions may be indicative of toxicosis, infection, or a defense mechanism. A statistically significant association between the nest position and renal oxalosis (renal calcium oxalate deposition) was observed. Renal oxalosis was probably due to the exceptionally high summer temperatures, which were statistically higher compared to the temperatures recorded in the previous two years.