engleski

Sexing of juvenile loggerhead sea turtles (Caretta caretta) : gonadal morphology vs. histology

Sea turtles exhibit sexual dimorphism only as adults, hence diagnosing the sex of hatchlings and juveniles request employment of different direct and indirect techniques which differ in the level of accuracy. With this study we therefore re-examined sex determination based upon gross morphology of reproductive organs of 99 juvenile loggerhead turtles with the curved carapace length (CCL) ranging from 24.0-69.0 cm (mean: 41.8 cm ; SD: 10.3) from the central and eastern Mediterranean by histological analysis of gonads. All the cases where the observer was unable to diagnose the sex from gross morphology of gonads or whereas the sex determination differed between these two methods were classified as the incorrectly diagnosed sex. Overall, the sex was correctly diagnosed in 92.9% of the 99 cases. The highest error rate (33.3%) was found in juveniles with CCL = 20.0 – 29.9 cm (N = 9), which strongly influenced the sex ratio estimates (visual = 0.60 ; histology = 2.00). In turtles with CCL = 30.0 – 39.9 cm (N = 38) and 40.0 – 49.9 cm (N = 30), the error rates were 5.3 and 6.7%, respectively, and have not resulted in a significant difference in sex ratios between the methods. In large immatures (CCL = 50.0 – 69.9 cm, N = 22), sex determination equalled 100% by both methods. Our results show that gonadal morphology is good as a sexing method in larger juveniles ; however in juveniles with CCL < 30 cm we strongly recommend verification of the results by histological examination of gonads.

sea turtles; sex determination; gonadal histology

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