In the United States, societal discussions are occurring about equal rights for members of the LGBT community. In this acronym, the T stands for transgendered, and the subject of today's post is about a fish species that embodies the concept of transgenderness. Actually, many species of fish could be highlighted as examples, but the California Sheephead (Semicossyphus pulcher), is the largest example of such a species along the California coast. When fully grown, adult male sheephead can reach a length of 3 ft (0.9 m), weigh 30 pounds (13.6 Kg), and reach a maximum age of about 20 years.
But beyond the statistics of size and age, the more interesting fact is that all sheephead are initially female. Only through social interactions and ecological factors do some undergo a hormonally-controlled transformation from female to male. This transformation can take between a couple of weeks and several months, and seems to be controlled by steroid hormone concentrations.
The transformation results not only in the complete degradation of the ovaries and the development of testes on the inside, the fish also undergo a marked external transformation. Female sheephead tend to be an overall pinkish color with a white jaw. A female sheephead can be seen exiting the frame of today's photo on the left behind the main subject. And can also be seen in today's photo, a male sheephead has a black head and tail, and a distinctive bright pink to red band in the middle of the body. Males also develop a large hump on the head, and lower jaw enlarges.
Sheephead are members of a family of fishes known as wrasses. Among wrasses, most of which are primarily tropical in distribution, this sex change performance is common, as is the development of harems, in which a single male defends a group of females from other males during times of spawning.
There is some scientific controversy about the female to male transformation. There is no doubt that it occurs, but the question is whether females can become males only after the dominant alpha male is removed from the group, or whether virtually all females will become males given enough time. Additionally, for most hermaphroditic species of fish, population densities and sex ratios are highly dependent on ecological factors. Thus the true answer to the question of how many females in a population will become males will vary from population to population and depend on a variety of factors that may differ between populations.
This photo was taken with a Canon EF17-40 mm f/4L USM lens zoomed to 17 mm on a Canon EOS 10D in an Ikelite underwater housing. Lighting was provided by two Ikelite DS-125 Substrobes in eTTL mode. The exposure was set to 1/60 sec at f/4 and ISO 100.
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