New insights into risk variables associated with gas embolism in loggerhead sea turtles (Caretta caretta) caught in trawls and gillnets

Comparative Diagnostic Efficacy of Ultrasonography and Radiography for Gas Embolism in Loggerhead (Caretta caretta) Turtles

Sea turtles face numerous threats, often stemming from human activities, resulting in high mortality rates. One of the primary risks they encounter is posed by fishing activities. In the South Adriatic Sea, the extensive trawling fleet often impacts sea turtles, and in recent years, a specific disorder, known as gas embolism (GE), and the associated disease known as decompression sickness (DCS), has emerged as a new threat. Our study aims to compare the statistical concordance and sensitivity, specificity, and accuracy between ultrasonography and radiography for evaluating GE in marine turtles. The study involved the analysis of 29 loggerhead turtles (Caretta caretta) admitted to the Sea Turtle Clinic (STC) at the Department of Veterinary Medicine, University of Bari, Italy, between December 2022 and March 2023. The sea turtles underwent X-ray evaluation using the three standard projections (dorso-ventral, latero-lateral, cranial-caudal), followed by ultrasound examination to visualize blood vessels through cervical, axillary, and inguinal ultrasound windows. Color Doppler ultrasonography was utilized to assess blood flow, gas localization, and quantity, but this technique proved to be less helpful in detecting GE. Our results confirm the statistically valid performance of ultrasonographic examinations, highlighting the significant role of combining ultrasonography and radiography to enhance sensitivity, especially in complex and challenging cases for identifying gas embolism (GE) in sea turtles.

Identifying biomarkers of pollutant exposure in ocean sentinels: Characterisation and optimisation of B-esterases in plasma from loggerhead turtles undergoing rehabilitation

Sea turtles are frequently proposed as indicator species for assessing ocean health. To faciliate the use of these species as bioindicators requires the development of tools for rapidly and effectively assessing individual health. Here, we collected 104 blood samples from 69 loggerhead sea turtles, Caretta caretta, undergoing rehabilitation to determine the connection between health status, the activity of B-esterases, and other biochemical parameters. To determine the optimal assay protocol for B-esterases, we measured the activity and kinetics of cholinesterases-(ChEs) and carboxylesterases (CEs) using 3 and 5 commercial substrates, respectively, at different assay conditions. IC50 values for the activity of B-esterases were calculated within a concentration range for model pesticide inhibitors. Turtles' health status was determined via routine veterinary procedures. During rehabilitation (which was associated with improving health status), we observed a decrease in the activity of most enzymes (especially in acetylcholinesterase) alongside an increase in CE when using p-nitrophenyl acetate as a substrate. As such, it is possible that the activity rates of plasmatic B-esterases could serve as an indicator of health status. There is also high potential that B-esterases could be specifically sensitive to marine pollutants although to further validate this would require future studies to specifically correlate B-esterarse activities to pollutant concentrations in blood or excreta.