Gonadial abnormalities in scombroid fishes

The most familiar case of ' Teratology ' in fishes is the incidence of hermaphroditism, the occurrence of both ovarian and testicular tissues in the same individual. A number of teleosts have been known from the time of Aristotle, to be functional hermaphrodites in which there is the production and the expulsion of ova and spermatozoa, simultaneously or at different times. Hermaphroditism is reported as an occasional abnormality in mackerels and tunas among Scombroid fishes. It is interesting to note that instances of this phenomenon have not so far been observed in the other two groups of Scombroid fishes, namely, billfishes and seerfishes. Though extensive work is being done in Scombroid fishes in different parts of the world, the paucity of records on the incidence of this phenomenon indicates that this is rather rare in occurrencein the natural populations of these fishes. The arrangement of the component parts of the gonads in the abnormal hermaphrodites among Scombroids so far observed shows a wide range of variation. In addition to hermaphroditism, certain other abnormalities in the ovaries have been observed in the oceanic skipjack Katsuwonus pelamis. A review of the instances of abnormalities in gonads of Scombroid fishes is presented herein