Genome analysis reveals ancient ancestor of snails and other mollusks

An international research team, led by scientists at the Senckenberg Centre for Human Evolution and Palaeoenvironment, has resolved a key evolutionary puzzle by analyzing 77 mollusk genomes. The study, published in the journal Science, reconstructs the evolutionary tree of mollusks, one of the most diverse animal groups on Earth, and provides insights into their ancient ancestor.

This ancestral mollusk, believed to have lived over 500 million years ago, likely had a robust shell, a foot for movement, lacked eyes, and possessed a radula, a characteristic rasp-like feeding organ. Mollusks exhibit vast genomic variability, which researchers suggest may explain their evolutionary success across diverse environments.

The research involved the sequencing of 13 new genomes from rare mollusk species by Senckenberg researchers. By combining this data with existing genomic information, the team constructed a detailed phylogenetic tree, confirming hypotheses about mollusk ancestry and resolving long-standing scientific debates.

The findings confirm an early split within mollusks into two main lineages: Aculifera, characterized by small spines, and Conchifera, encompassing snails, bivalves, and cephalopods. The study proposes a new grouping, "Megalopodifera," which includes snails, bivalves, and scaphopods, highlighting rapid diversification from a common ancestor with a large foot.