Kweku Monney, University of Cape Coast, Ghana

Some species of giant African snails (Achatinidae) exhibit polymorphism in the colour and pigmentation of the shell and/or body. In parts of West Africa where these snails are collected for food, one morph of the same species may be more popular.

In Nigeria, people avoid collecting the white (albino) form of an unidentified species for a number of cultural and medicinal reasons (Owen & Reid, 1986). Some tribes in Togo and Benin use the albinos in the practice of magic.

In Ghana, a rare albino of Achatina achatina described locally as "king snail" is prized very much for its sheer rarity and aesthetic value. However, in the same country, the albino of Archachatina marginata (see Fig. 1) does not command such popularity. Individuals of Archachatina marginata,,commonly called "margies",. may have a dark or white body. The dark or white bodied morphs are indistinguishable if the animal withdraws into the shell and is in a normal resting position. The albinos are generally described as "ghost" snails or "barry whites" and thought by collectors to be a different species. Currently, in most populations there is a preponderance of white bodied snails over the dark ones, because snail collectors generally refuse to pick the former. This leads to different prices of the two morphs in the local markets. The price of dark bodied is about three times that of white bodied for the same weight of snails. People are eventually persuaded to eat the albinos if it is explained to them that the albinos lack just a skin pigment, i.e. melanin.

The contribution of this selective human predation must not be overlooked in the study of the genetic basis and maintenance of polymorphism in giant African snails.

Reference

Owen, D. F. & Reid, J. C. (1986). The white snails of Africa- the significance of man in the maintenance of a striking polymorphism. Oikos, 46: 267-269.