Article Review
Author(s): Maria P. Ikonomopoulou, Rachel C. Aland, Kamarrudin Ibrahim, Edward Gosden, and Joan M. Whittier
The sex of a sea turtle is determined by the temperature surrounding the egg in the nest, also known as temperature-dependant sex determination. Before becoming a male or female, the gonads of the embryo are the same. The gonads are created from a mass of cells that become differentiated into ovaries or testis. By increasing the number of cells in the cortex and decreasing the cells in the medulla, the female gonads are formed. Testes develop through “cortical regression and differentiation of seminiferous cords in the medulla of the gonad”. Both males and females develop a paramesonephric duct, but this is prominent in females and degenerated in males.
At optimal temperatures, the nest produces approximately a 50:50 ratio of males and females. Rising above the optimal temperatures gives mostly females, and males are mostly produced when the temperature is lower than desired. If the temperature is optimal for part of the nesting period and then suddenly changes, intersexuality occurs. Intersexuality is the term used when a baby has no sex after birth, but can develop either female or male sex organs within the next couple of months. The sex of a turtle can be determined using genes, such as SOX 9 for males and Wnt4 for females. Also, the carapace can be studied to figure out the sex of a hatchling. Large hatchlings can be sexed using laparoscopy; however, many methods can be used that are more invasive, such as assays of plasma sex steroids or analyzing amniotic fluid, but these methods require a lot of training.
The objective of this research was to replace old qualitative methods with a more objective set of quantitative methods to sex turtles. These methods include measuring the paramesonephic duct epithelium, “the height of the nucleus in cells within the gonadal cortical epithelium, and the width of the gonadal ridge”.
These quantitative methods of sexing turtles can be used by inexperienced researchers. The visual sexing using the PMN duct is necessary. This research is important so that invasive sexing procedures can be reserved for extreme situations, whereas the easier methods can be harmlessly used. If the methods of sexing were easier, more people would be able to sex turtles, making it easier for knowledge of turtles to be passed along.
Article Courtesy of: http://www.bioone.org/doi/pdf/10.1670/10-333
Photos Courtesy of: http://webecoist.momtastic.com/2008/11/16/8-coolest-scaliest-endangered-species/gex_green-sea-turtle/
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