Image_3_Development of an enzyme-linked immunosorbent assay for determining FSH plasma concentrations in green sea turtle (Chelonia mydas), using recombinant gonadotropins.tif

Follicle-stimulating hormone (FSH) is involved in the regulation of essential reproductive processes such as gametogenesis and follicular growth. There are presently no immunoassays for measuring FSH in turtles. Recently we produced green sea turtle (Chelonia mydas) recombinant (r) FSH as a single-chain polypeptide using the methylotrophic yeast Pichia pastoris expression system, and polyclonal antibodies for the recombinant FSH. In this work we developed a competitive enzyme-linked immunosorbent assay (ELISA) for the measurement of FSH concentrations in plasma samples from green sea turtles. We used the rFSHβα for standard, rFSHβ for coating and a cmFSHβ antibody. The sensitivity of the assay was 0.13 ng/ml and the intra-assay and inter-assay coefficients of variation were 5.54% and 13.52% respectively. Parallelism was observed between the linearized FSH standard curves and the corresponding serial dilutions of green sea turtle plasma samples. We also observed parallelism between the linearized standard and serial dilutions of plasma samples from the loggerhead sea turtle (Caretta caretta), hawksbill sea turtle (Eretmochelys imbricate), and African softshell turtle (Trionyx triunguis). The ELISA was used to study the FSH plasma concentrations during the reproductive cycles and was compared to hormonal steroid concentrations (Testosterone, Estradiol and Progesterone). This revealed a positive correlation between FSH and estradiol concentrations in females; estradiol concentrations were increased immediately after FSH elevation. In addition, nested females presented an increase in FSH concentrations prior to progesterone elevation in January to April, slightly before egg laying. This ELISA will increase our understanding of gonadotropin functions, and their effects on reproduction in the green sea turtle.</p

A small fishery with a high impact on sea turtle populations in the eastern Mediterranean

<div><p>Sea turtles were targeted by fisheries in the Mediterranean from 1920 to 1970 and have undergone severe exploitation. At least 30,000 to 40,000 turtles were caught along the Palestinian coastline during the 1920s to 1930s. Although intentional cap- ture of marine turtles is now illegal, sea turtles are still incidentally caught by the fishing industry, making it a major cause of sea turtle mortality. The present study as- sesses the impact of the Israeli fishery fleet on the turtle population in the Levantine basin based on on-board observations and a fishermen survey. The results show that gillnets and trawlers are the main threats to sea turtles in this area. 21 turtles were caught during 1385.5 hours of trawling observations – a catch rate of 0.015 turtles per hour. We estimate that a total of 1,315 turtles are caught annually by Israeli trawlers. According to the fishermen survey, ∼21 turtles are caught each year by a single gillnet vessel, yielding an annual estimate of 1,672 turtles for the whole gillnet fleet. We have also found that only a small fraction of the turtles injured by trawlers is represented in the strandings. The mortality rate through trawling and the stranding density is the highest in the region, emphasizing the urgent need to regulate the Israe- li fishery. This fishery poses a major threat to the whole Levantine sea turtle popula- tion, especially during the vulnerable reproduction stage.</p></div