The shell of bivalve molluscs, which is the most distinct feature of the group, exhibits a large degree of morphological variation in many species. Such variability is attributable to a combination of genotypic and environmental influences. Cryptic species of the smooth-shelled blue mussel Mytilus edulis complex possess subtle morphological differences, which make them an interesting model system to evaluate inter- and intraspecific morphological variation. Differences in shell morphology of the bivalve molluscs M. edulis, Mytilus galloprovincialis and Mytilus chilensis were studied from a number of Pacific Ocean coastal sites within the latitudinal distribution range of these mussels in southern Chile. Species status was determined by molecular identification techniques (restriction fragment length polymorphism assays, Me15/16 and COIXba) before nine anatomical landmarks, involving the umbo, ligament, posterior abductor muscle scars, posterior border and ventral area, were used to characterize shell shape. A canonical variate analysis scatter plot was used to present the clustering of each species graphically, and relative warp analysis and Goodall's F-test were used to test for differences in anatomical landmarks between pairs of the three Mytilus species. Significant differences were found in the landmark morphology and the shell shape of the three species, with shell elongation of the dorsal region being significantly different amongst M. edulis, M. galloprovincialis and M. chilensis. Our analyses also revealed a latitudinal pattern in the morphology of the shell of M. chilensis, with the northern and southern shell forms being found in areas consistent with a known biogeographical break between cooler (southern) and warmer (northern) waters along the coast.
Áreas temáticas de ASJC Scopus
- Ecología, evolución, comportamiento y sistemática