A hermaphrodite is an individual or species that contains both male and female sexual organs at some point during their lives. Generally, hermaphroditism occurs in the invertebrates, although it occurs in a fair number of fishes, and to a lesser degree in the higher organisms. This term includes:
- Sequential hermaphrodite: The organism is born as one sex and later changes into the other sex.
- Protandry: When the organism starts as a male, and changes sex to a female later in life. Example: The seabasses (Family Serranidae). These are a highly sought food fish complex made up of primarily groupers. Since even a small male can produce more than enough sperm to fertilize a huge number of eggs, while a female's egg output increases greatly with an increase in size, this strategy makes sense for an organism (fishes in general) where over 99% of the eggs laid will not result in a fish that reaches sexual maturity. It has been shown that fishing pressure actually is causing a change in when the switch from male to female occurs, since fishermen naturally prefer to catch the larger fishes. The populations are generally changing sex at a smaller size, due to natural selection.
- Protogyny: When the organism starts as a female, and changes sex to a male later in life. Example: Wrasses (Family Labridae) are reef fishes that tend to have three distinct sexual types. Small females, immature males and supermales. The small females and the immature males have identical colorations. The supermale is usually brightly colored, and there is only one in a given area of the reef. This supermale dominates the other wrasses of the species, having the choice of females to mate with. When the supermale dies, the largest wrasse in the area, male or'' female, becomes the new supermale.
- Simultaneous hermaphrodite: The organism has both male and female sexual organs at the same time as an adult. Usually, self-fertilization does not occur. Also called synchronous hermaphrodites. Examples: Earthworms. Hamlets (Family Haemulidae) are a type of fish that are curious for many reasons, including that they seem to be evolving into different species quite rapidly. Unlike other fishes, hamlets seem quite at ease mating in front of divers, allowing observations in the wild to occur readily. They do not practice self fertilization, but when they find a mate, the pair takes turns between which one acts as the male, and which acts as the female, through multiple matings, usually over several nights.
The term "hermaphrodite" derives from Hermaphroditus, the son of Hermes and Aphrodite in Greek mythology, who was fused with a nymph, resulting in one being possessing physical traits of both sexes.
See also: Intersexuals (human versions)