Yellow Umbrella Slug

Tylodina fungina

Tylodina fungina is a marine gastropod that can be identified by its bright sulfur yellow body and a conical, limpet-like shell that varies in color from white to pinkish brown, often adorned with small brown bristles and markings. Adults typically measure between 3 to 6 cm in length, while juveniles are smaller and have flatter, more translucent shells. The slug's rhinophores are rolled and have eyes at their base, giving it a resemblance to a capped mushroom, which is reflected in its alternative common name, mushroom sidegill. This species inhabits the eastern Pacific Ocean, ranging from Cayucos in California to Banderas Bay in Mexico, including the Galapagos Islands. They are often found in the intertidal zone and can be observed at depths of 10 to 20 feet underwater. The yellow umbrella slug primarily feeds on the yellow sulfur sponge, Aplysina fistularis, and is believed to have a specialized diet that focuses exclusively on this sponge. Encounters with Tylodina fungina during dives can be intriguing, as divers may spot them clinging to their preferred sponge in shallow waters. Their unique appearance and behavior can make for interesting photographic subjects, especially in their natural habitat. The species has not been evaluated by the IUCN, leaving its conservation status unknown.