Eggs sunny-side up: A new species of Olea, an unusual oophagous sea slug (Gastropoda: Heterobranchia: Sacoglossa), from the western Atlantic.

Nearly all of the recognized species of sea slugs in clade Sacoglossa (about 300 taxa) are herbivorous, using a uniseriate radula in suctorial feeding. The only exceptions are a pair of monotypic genera in the ceratiform family Limapontiidae: Olea Agersborg, 1923 from the northeastern Pacific, and Calliopaea d'Orbigny, 1837 from the northeastern Atlantic coast of Europe and the Mediterranean. Both genera feed on the eggs of other heterobranchs, notably cephalaspideans, and lack cerata on the anterior dorsum. Major differences are that C. bellula d'Orbigny, 1837 has more cerata than O. hansineensis Agersborg, 1923, a more typical radula with ascending and descending rows of fully-formed teeth, and a much longer penial stylet. Here, we describe a new egg-eating sacoglossan species from the subtropical Gulf of Mexico coast of Florida, U.S.A. Phylogenetic relationships inferred from analyses of a four-gene dataset including 219 sacoglossan species indicated the new taxon (O. hensoni n. sp.) belongs to Olea. The generic placement of the new species is also supported by its highly reduced radula and comparatively short penial stylet. A full description of the reproductive, digestive, and nervous systems is also provided. Finding a new Olea species in the warm waters of the western Atlantic was surprising, given the genus was previously known only from the cold northern Pacific, and suggests further diversity in oophagous sacoglossans may await discovery.