Colloidal Sperm-Packing in Mouthbrooding Tilapiine Fishes
Grier HJ. 1995. Colloidal Sperm-Packing in Mouthbrooding Tilapiine Fishes. Copeia. 1995(4):966-970
Mode of reproduction is one of the characteristics used to distinguish the tilapiine genera Tilapia, Sarotherodon, and Oreochromis (Trewavas, 1981, 1983). Species in the genus Tilapia are substrate spawners; whereas species in the other two genera are mouthbrooders. In the genus Sarotherodon, single males occupy a breeding area, and mouth brooding may be either biparental, as in Sarotherodon galilaeus, or paternal, as in Sarotherodon melanotheron. Virtually all species of Oreochromis are maternal mouthbrooders. Breeding males congregate in breeding arenas or leks, each defending its spawning territory while awaiting a gravid female who spawns during a short visit. Species in each of the genera have distinctive spawning behaviors (F1shelson, 1983). In Tilapia, breeders clean the spawning surface, and females lay lines of adhesive eggs which are fertilized by males. Pairs of spawning S. galilaeus deposit their spawn onto the substrate prior to picking up eggs in their mouths (Fishelson and Heinrich, 1963; Fryer and Isles, 1972). Oreochromis females lay small groups of eggs and pick them up in their mouths; eggs are fertilized while on the bottom or when they are in the female's mouth (Trewavas, 1981 ). Testes of four species in these three genera were examined histologically so that anatomical differences that might relate to the different spawning behaviors could be determined.