The Biology and Culture of Tilapias

Tilapias: Taxonomy and Speciation

Fish Section

British Museum (Natuml History)

Cromwell Road, South Kensington

London, S. W. 7, England

TREWAVAS. E. 1982. Tilapias: taxonomy and speciation, p. 3-13. In R.S.V.

Pullin and R.H. Lowe-McConnell (eds.) The biology and culture of tilapias.

ICLARM Conference Proceedings 7, 432 p. International Center for

Living Aquatic Resources Management, Manila, Philippines.

The tilapias are here grouped into two genera, Tilapia and Sarotherodon,

characterized by both their feeding and their reproductive habits and struc-

tures. There is some overlap in feeding habits, some species of both genera

feeding on detritus and periphyton, but substrate-spawning and mouthbrood-

ing respectively characterize the two genera.

The mouthbrooding of the species of Sarotherodon is of two main types,

biparental or parental in subgenus Sarotherodon (in the restricted sense) and

maternal brooding with mating of a lek pattern in the rest, The maternal

mouthbrooders have been divided into several (5 to 7) subgenera: Oreo-

chromis, Danakilia, Alcolapia, Nyasalapia and Neotihpia are recognized here.

Speciation, both allopatric and sympatric, of subgenus Sarotherodon has

taken place in west Africa, and of the other subgenera mostly in east and

central Africa. There is no doubt that the division between subgenus Saro-

therodon and other subgenera is deeper than the divisions within the latter.

For this reason some authors (Thys, Peters) prefer a generic grouping that

goes no lower than Tilapia, but the mouthbrooding subgenera have so much

in common that they must have descended from one or a few closely related

substrate-spawning species, and grouping them all at the generic level seems

to have both theoretical and practical justification.

An example is given of the importance of recognizing specific distinctions.

Biology and Taxonomy

All the tilapias, in the broad sense, have in common a mainly herbivorous
diet, in distinction to the majority of fishes which feed predominantly on
small invertebrates or on young or srnall-sized fishes. They are therefore only
one step &om the primary producers (plant life) and as they grow to a good
size they are a valuable food source for man, the omnivore.
Structural adaptations to this diet are the long, coiled intestine, which
may be up to fourteen times the body length, the bicuspid and tricuspid
teeth of the jaws and the small, sharp pharyngeal teeth used to prepare
the food by shredding the coarser materials and breaking some of the celI
walls before passing it on to the stomach. Since the preferred diet of the