ESTERASE VARIABILITY IN THE GASTROPODS LITTORINA SAXATILIS (OLIVI) AND L. ARCANA ELLIS

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Abstract
The esterase system has been studied using isoelectric focusing in two closely related rough periwinkles, Littorina saxatilis and L. arcana, in an investigation of possible differences between the two species at this level of discrimination. Collections of both species were obtained from Yorkshire, north Cornwall and south Devon [UK], L. saxatilis was also obtained from sites in south Cornwall (in and near the estuary of the Tamar), Dorset and Scotland, where L. arcana was not present. There is considerable variation both within and between sites which tends to mask any overall differences between the two species. However, in general there is a much greater degree of heterogeneity within samples of L. saxatilis than within samples of L. arcana when both species are found together; this is reflected in the Shannon Wiener diversity index for bands. Also the number of esterase bands is greater for L. saxatilis than for L. arcana at each of the five sites where both occurred. A dendrogram derived from the percentage occurrence of each band present in each sample produced a reasonable degree of separation of the two species.