Food induced esterase phenocopies in the snail Cepaea nemoralis

Hepatopancreatic extracts from the snail Cepaea nemoralis, assayed straight from the field, often contain three or four heavily staining esterase zones which migrate to the cathodal end of polyacrylamide disc gels during electrophoresis. Previous breeding results showed that the heavily straining zones appeared allelic but to incorporate these multibanded phenotypes, a super gene of five closely linked loci was tentatively proposed. Further breeding work again failed to demonstrate multiple zones in parents or offspring and so experiments were conducted to see whether the multi-zoned phenotypes in the wild were produced by secondary modification of single primary products. Wild snails yielding extracts containing more than two heavily staining zones were shown to possess only two such zones after three months under laboratory conditions. Also, the ingestion of nettle (Urtica dioica L.) has been demonstrated to induce extra esterase zones in laboratory-reared animals. Some of the secondarily induced zones appear identical in physical, biochemical and electrophoretic properties to the primary products of other alleles, and thus appear to be electrophoretic phenocopies. A model is suggested which could account for this phenomenon.