Principles of Genetics and Breeding

4.1.4 Hermaphroditism

• Hermaphroditism is the possession of both ovarian and testicular tissues in the same individual fish which functions both as male and female during its life history.

• About 130 cases of hermaphroditism have been reported in various species of fishes. All the types of gonadal sexes such as gonochorists and synchronous, protogynous, and protandrous hermaphrodites are found in serranids and sparids.

• The genetic mechanism of sex determination is apparently lacking in all hermaphrodite fish species.

• In the hermaphrodites of Tilapia zilli,it had been suggested that ovatestes may be nonfunctional.

• Occasional hermaphrodites were reported in many fish species normally having two distinct sexes.

• Hermaphrodites have been described in white fishes, common carp and in the guppy. Self-fertilization is also possible in the common carp and guppy.

• Spontaneous synchronous hermaphroditism is sometimes found in natural environments in Oncorhynchus keta. They are also reported in caregonids and clupeids. There are three types of hermaphroditism: synchronous (balanced), protogynous and protandrous.