Meeting Abstract
Rotifera sensu stricto (minus Acanthocephala) is a well-defined lineage with several autapomorphic characters that include a ciliated corona, muscular pharynx with hardened jaws (trophi), and syncytial epidermis with intracytoplasmic lamina. The corona is often the most recognizable feature in rotifers as it comprises two circumapical rings of cilia at the anterior end, often elaborated into a series of lobes or wheel-like structures that function in locomotion and feeding. Despite the vast diversity of coronal shapes and sizes, the corona is hypothesized to be homologous throughout the phylum. However, a select clade of rotifers, the Collothecaceae (Monogononta: Superorder Gnesiotrocha), consists of species that have a corona as larvae but lack one as an adult. When larvae settle, they undergo a remarkable metamorphosis wherein the corona is completely replaced by an entirely new head called the infundibulum. The infundibulum is cup-shaped and often adorned with setae and/or tentacles. Despite the obvious differences between the corona and infundibulum, both structures are often considered homologous in the taxonomic literature, and the infundibulum is hypothesized to be a derived form of corona. However, recent results call this hypothesis into question. Here we present evidence to suggest that the infundibulum is unique to species of Collothecaceae and not homologous with the corona. We use data derived from studies of larval and adult morphology and development to show that the infundibulum is a derivative of the larval foregut and not the larval corona.
