Student Stuff
Gonads
The sexes of fishes are usually separate. Males usually have paired testes that produce sperm, and females usually have paired ovaries that produce eggs.
When paired, such as in the Blue Mackerel, the gonads lie on either side of the swim bladder. The method by which the eggs and sperm meet and thus fertilisation occurs varies widely among fishes. Many species are broadcast spawners, shedding their eggs and sperm into the water to fertilise external to the body. Other species such as sharks and rays have internal fertilisation where the sperm are released into the body of the female. Many variations exist, including the seahorse, in which the female deposits her eggs into the pouch of the male where they are fertilised.
The hagfishes and lampreys have a single ovary or testis. Sperm and eggs are shed into the body cavity and out through a urogenital papilla.
Further reading
- Helfman G.S., Collette, B.B. & D.E. Facey. 1997. The Diversity of Fishes. Blackwell Science. Pp. 528.
- Lagler, K.F, J.E Bardach & Miller R.R. 1962. Ichthyology. John Wiley & sons. Pp. 545.
