Lost and found: Totton’s Minyaspis faroni revived and molecular evidence of paraphyly of Oxynaspis and Minyaspis

The stalked barnacles Minyaspis faroni associated with antipatharians known from the southern Red Sea have been recently recorded in the northern Red Sea. Two genera of oxynaspids, Oxyaspis and Minyaspis, differ morphologically in the coverage of the capitulum. In Oxyaspis, the capitulum is covered by calcified plates, whereas in Minyaspis, the plates are reduced, and there is an uncalcified area between plates. Molecular analyses revealed that species with reduced plates do not cluster in the same clade, whereas species with full coverage and uncalcified capitula are found in the same clade. Our analysis indicates that the reduction of opercular plates in the epibiotic barnacles has occurred more than once in the barnacle evolutionary pathway. The reduction in shell plates’ number, size, shape and thickness is an adaptive character of epibiotic symbiosis. This mode of life, common in thoracican barnacles, leads to adaptive morphological changes. Hence, the morphology of shell plates is not a homologous feature but reflects parallel evolution.