Academic journal article The Science Teacher

Ask the Experts: Providing Answers to Science Questions

Academic journal article The Science Teacher

Ask the Experts: Providing Answers to Science Questions

Article excerpt

Q How does temperature regulate the gender of sea turtles (and other organisms) as they incubate? Also, how can XX females become male turtles simply due to temperature level if they do not have a Y chromosome to begin with?

Greg McDonald

Biology and Aquatic Science Teacher

Westchester Academy

for International Studies

Houston, TX

A First, it is important to accept the idea that genes do not directly control the development of sex organs in some organisms. Many species of reptiles have no sex chromosomes or specific genes that control the expressed (phenotypic) sex. According to an article that appeared in the Journal of Reproductive Biology and Endocrinology, "Many species of reptiles, including most terrestrial turtles and all crocodilians and sea turtles examined to this date, have no discernible sex chromosomes, nor is their sex determined by the presence or absence of specific genes" (Manolakou, Lavranos, and Angelopoulou 2006). There are a number of reptiles whose sex is temperature-dependent. In green sea turtles, incubation temperatures below 28[degrees]C during a key developmental stage result in mostly male hatchlings; temperatures above 28[degrees]C result in mostly females.

Chemical activity may have more to do with turtle gender than chromosomes. The enzyme aromatase becomes very active in the middle third of a turtle embryo's development period. Aromatase converts androgens into estrogens. Warmer temperatures during this stage of development promote greater aromatase activity, which chemically stimulates the formation of ovaries. At lower temperatures, lower aromatase levels lead to embryonic development of testes.

Q Will we experience increased volcanic activity if the sea level rises due to human-induced global warming? …

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