Hilton's Aeolid

Phidiana hiltoni

Hilton's Aeolid, a species of sea slug, is a shell-less marine gastropod that can reach a length of up to 50 mm, or just over 2 inches. It is characterized by a reddish or brownish line across its head, a distinctive feature that helps in identifying this species. Divers may confuse it with Hermissenda crassicornis, which has a similar appearance but lacks the same head markings. This nudibranch is typically found along the central California coast to Baja California, Mexico, and its range has been extending northward, now reaching areas north of San Francisco Bay. This species inhabits benthic environments and is usually found at depths ranging from 0 to 28 meters, with most occurrences recorded shallower than 20 meters. Hilton's Aeolid feeds on Hydractinia sp., showcasing its role in the local ecosystem. It exhibits aggressive behavior, often engaging in biting and fighting with other nudibranchs, including its own species, which can make encounters with this nudibranch particularly interesting for divers. As a simultaneous hermaphrodite, Hilton's Aeolid has a unique mating behavior where individuals will engage in a ritual to determine which will act as male and which as female. Eggs are laid on a suitable substrate, where they develop into planktonic larvae before maturing into adults. Although the conservation status of this species has not been evaluated, it is recorded at multiple dive sites, indicating a notable presence in its range.