ABSTRACT
Intersexuality is the simultaneous existence of male and female characteristics in a single individual. In fact, all hermaphrodites are intersexes, but some intersexes are not hermaphrodites. Essentially, there is mutual tolerance between the two opposing sexual tendencies in the hermaphrodites. Conversely, intersexuality is the result of interference between the two opposing sexual tendencies, neither of which can therefore express itself decisively (Atz, 1964). In fact, intersexuality is a state from which many fi shes pass through during the early stage of their gonadal development (e.g. threadfi n bream Nemipterus bathybius, Takahashi et al., 1989) and during the adult stage of sequential and serial hermaphrodites (Cole, 2008). However, permanently functional intersexuality in adult fi shes has so far not been reported, although very rarely partially functioning intersexual abnormality has been reported only once. A valuable list summarizing the available records dating from 1867 to 1963 on abnormal intersexuality in teleosts is summarized by Atz (1964). Of 90 and odd reports on the simultaneous presence of ovary and testis in an individual, the presence of an ovotestis is the most frequent; the number of reports available is: ovotestis 3, functional ovotestis 1, ovotestis + ovary 8, ovotestis + testis 8. In those with ovary and testis (3 cases), the abnormality ranges from a pair of ovaries with another pair of testes (e.g. tiger buffer Takifugu rubripes, Suzuki, 1997) to three gonads and to a testis on one side with an ovary on the other; in the others with ovotestis, a pair of asymmetrical ovotestes is the most common arrangement; however, the testicular portions are mainly located posteriorly and in at least fi ve cases, the testicular portion is only attached to the ovary. Oocytes and eggs are found in a testis or testes in nine cases. It is not clear how the anatomical structure of one functional ovotestis was accommodated in the superfoetid viviparous guppy Poecilia reticulata. A similar apparently functional intersex was also described in Rutilus rutilus (Jafri and Ensor, 1979). From a simultaneous hermaphroditic carp maintained under controlled conditions, Kossman (1971) stripped sperm and eggs and successfully fertilized them.
