Climate and predation dominate juvenile and adult recruitment in a turtle with temperature-dependent sex determination. Genotypic sex determination enabled adaptive radiations of extinct marine reptiles. Sex-determining mechanisms in reptiles are broadly divided into two main categories: genotypic sex determination GSD and temperature-dependent sex determination TSD.
Quinn et al.
In the late s, James J. For example, while amh clearly lies far downstream in the sex determination pathway and is controlled by sox9it has been shown in chicken that the expression of amh precedes that of sox9 in males [ 5556 ]. These novel master SD genes highlight the importance of non-transcriptional factors in sex determination since three of these genes i.
It will be interesting to compare the expression profile of amh in fish species with TSD and GSD, or fish species with different levels of TSD varying levels of sex ratio response to temperature, e. When Bull and Eric Charnov, at the University of Utah, in Salt Lake City, Utah, proposed a model for the evolution of environmental sex determination inthey only suggested applying the model to plants and invertebrates, and not to vertebrates.
We expect that this mortality difference may be most pronounced in adulthood, when sexually selected traits are fully expressed. Temperature pulses during the thermosensitive period are often sufficient to determine sex, but after the TSP, sex is unresponsive to temperature.
Related Services View all. Sign In See Subscription Options. Moreover, the sensitive time for the effects of estrogens and their inhibitors coincides with the time when sex determination usually occurs Bull et al. The estrogen synthesis inhibitors used in the experiments mentioned above worked by blocking the aromatase enzyme, showing that experimentally low aromatase conditions yield male offspring.
They conjectured that disruptive selection produced by variation in the environment could result in an evolutionary transition from ESD to GSD Bull, Vogt, and Bulmer, Turtles of the World. In most species, gender is determined during fertilization. You have free article s left.
Nottingham: Nottingham University Press. Related Services View all.