RNA, Ribosomal, 18S - genetics, Phylogeny, Chi-Square Distribution, Sequence Analysis, DNA, Sequence Alignment, Animals, Gastropoda - classification, Ecosystem, Bayes Theorem, Polymerase Chain Reaction, Gastropoda - genetics, RNA, Ribosomal, 28S - genetics, Evolution, Molecular, Molecular evolution, Mollusks, Genetic aspects, Research