Chthamalus proteus sp. nov. is described as a distinct species based on its clear separation by starch-gel electrophoresis of enzymes. A redescription is given of C. fragilis , a related species, which differs absolutely from C. proteus in 3 out of 16 enzymes. Given the distinction of C. proteus from C. fragilis by enzyme methods, it has been possible to devise morphological criteria, involving simple measurements of the opercular valves and first maxilla, which can separate the two species in 99% of individuals. Although the morphological characters overlap slightly, the enzyme results show no evidence of hybridization. A species previously confused with C. proteus, C. bisinuatus from Brazil, differs considerably in morphology and is briefly redescribed. C. proteus appears to have a tropical distribution; it extends from the Gulf of Mexico to Trinidad, and perhaps also occurs from Recife to south of Rio de Janeiro in Brazil. In contrast, C. fragilis is a warm-temperate species which is distributed from New England to southern Florida, but overlaps with C. proteus in the Gulf of Mexico. C. proteus and C. fragilis belong to a group of Chthamalus species which are morphologically similar, and are most easily separated by enzyme characters. The other members of this group are found along the eastern coast of the Pacific from California to Peru, and it is conceivable they all had a common origin before the formation of the present isthmus of Panama. A sample of C. proteus from the northern Gulf of Mexico showed very significant differences in allozyme frequency when compared with samples from southern Florida and Trinidad. The differences are of similar character to those found between a sample of C. montagui from Venice and samples from south-west England, and may be a result of environmental influences. |
