The amino acid composition of freshwater mollusc shells in relation to phylogeny and environment

Quantitative thin layer chromatography of structural amino acids was standardized for the study of shell proteins of 13 species of freshwater mollusc. There was slight intraspecific variation between individuals, particularly for tyrosine concentrations. No external periostracum was chemically identifiable in the shell of Lymnaea peregra (Muller) and this species showed some amino acid heterogeneity in different parts of the shell. Despite these intraspecific variations, analysis of variance suggested interspecific variation in concentrations for almost all the amino acids studied. Cluster and principal components analysis indicated that the amino acid composition did reflect phylogenetic affinity but that environmental factors were probably more important.