Hermaphoditism is rather common in fish; approximately 2 percent of all extant teleost species are hermaphroditic. Hermaphroditism isn't confined to one classification order or family; fish in nine orders in more than 20 families are hermaphrodites, according to the 2008 "Karger Sexual Development" article "Evolutionary Perspectives on Hermaphroditism in Fishes" by J.C. Avise and J.E. Mank.
Synchronous and Simultaneous Hermaphroditism
When it comes to hermaphrodite fishes, several terms define the range of hermaphroditism. In synchronous and simultaneous hermaphroditism, fish have an ovary and a testis, or an ovotestis. This type of hermaphroditism is most common in fish who inhabit the dark depths of the ocean in low-population densities. This type of hermaphroditism is advantageous, as these fish tend to be continuously sexually mature -- meaning a chance encounter with a conspecific is almost always productive. Examples include sand perch (Diplectrum formosum), longnose lancetfish (Alepisaurus ferox) and many sea basses (Serranidae).
Sequential hermaphrodites start off as one sex and switch to the other if the need arises, such as when the breeding member of one sex is removed by death or other means. Sequential hermaphroditism can be categorized as either protandrous, meaning the fish start out as males, or protogynous, where the fish start out as females.
Protogynous hermaphroditism is more common in fish than the other types of hermaphroditism are. Protogyny is found in at least 14 families, 11 of which inhabit the warmer climates around coral reef systems. Large groupers (Serranidae), such as the 4-foot-long, 50-pound Nassau grouper (Epinephelus striatus), parrotfishes (Scaridae) and wrasses (Labridae), such as the bluehead wrasse (Thalassoma bifasciatium), are all examples of protogynous hermaphrodites.
Protandry is less common than protogyny, occurring in eight families. Examples of protogynous fish species include porgies (Sparidae), damselfishes (Pomacentridae) and moray eels (Muraenidae). Clownfishes (Amphiprion spp.), members of the damselfish family, are familiar to many people because of their popularity in aquaculture and movies. These three families are common in coral reef systems; many coral reef fishes are hermaphroditic.
- University of California Irvine; "Evolutionary Perspectives on Hermaphroditism in Fishes"; J.C. Avise, et al; 2009
- University of California Press: Fish Reproduction
- University of Idaho Fish Physiology Class: Reproduction & Recovery - Or Not
- Ichthyology at the Florida Museum of Natural History: Sand Perch
- American Scientist; Mating Behavior and Hermaphroditism in Coral Reef Fishes; Robert R. Warner
- Ichthyology at the Florida Museum of Natural History: Nassau Grouper
- Comstock Images/Comstock/Getty Images