Enzyme variation in Chthamalus stellatus and Chthamalus montagui (Crustacea: Cirripedia): evidence for the presence of C. montagui in the Adriatic.

The electrophoretic mobilities of 13 enzymes in two species of Chthamalus, C.stellatus Poli and C. montagui Southward, were compared. These species differed absolutely for eight of the enzymes and exhibited some species-specific allozymes for a further four enzymes. No evidence of hybridization was found. The observed mean heterozygosity was 0.087 for C. stellatus and 0.179 for C. montagui. A sample of 'C. montagui' from Venice differed from two samples from south-west England in external shell characters and in allozyme frequency for two enzymes. These differences are thought to be the result of a geographical cline rather than a distinct separation of subspecies