Tylodinadae Family of False Limpets

One False Limpet of the Tylodinadae Family can be found in this website:

Yellow Umbrella Slug, Tylodina fungina.  A representative of the Tylodinidae Family of False Limpets.

Phylogeny: False Limpets of the Tylodinidae Family are in the phylum Mollusca. They are in the class Gastropoda and the subclass Heterobranchia  of “different-gilled snails”. They are in the Euthyneura infraclass, the Tectipleura subterclass, the Tectipleura superorder, and the Umbraculida order. Species in this order are sea slugs with a dorsal cap-like shell and gills on their right side. The superfamily Umbraculoidea is the only superfamily in this order. The Tylodinidae Family is one of two families in this superfamily. The Tylodinidae Family is small, with only one genus and seven species. These mollusks are also commonly known as Side-gilled Slugs or Tylodinids. The name Tylodinidae comes from the Greek root word meaning “knob” or “lump”, and refers to the hump-like shape of these animals.

Morphology: False Limpets of the Tylodinidae Family are medium to large in size, bright yellow, and elongate. The head displays  a pair of rolled rhinophores,  a flat frontal veil, and two eyes. Their dorsal mantle is well developed, smooth, and completely covers the body. The foot is broad and has a rounded tail. The dorsum is partially covered by a thin, transparent, patelliform (cap-like) shell. The shell is ovate in outline and increases in steepness and height with age. The shell is covered by a periostracum.  The mantle cavity is located between the mantle and the foot on the right side of the body. The mantle cavity contains the bipinnate gills. The largest species in the Tylodinidae Family reach 12.0 cm (4.7 inches) in length.

Habitat and Distribution: Tylodinid False Limpets are usually found on rocks or on the sponges that they prey upon. They live in the intertidal zone and to depths exceeding 145 m (476 feet). Tylodinid False Limpets are found worldwide in temperate to tropical seas. The Yellow Umbrella Slug Tylodina fungina is the only species from the Tylodinidae Family found in Mexican waters.

Reproduction: Tylodinid False Limpets are simultaneous hermaphrodites (having both male and female reproductive organs). They reproduce sexually with internal fertilization. Fertilization is reciprocal. The eggs are laid as an irregular ribbon-like egg mass.

Ecosystem Roles:  Tylodinid False Limpets feed on sponges, using their radula (rasp-like teeth)  to assist with that process. They can store toxins from their prey in glands in their mantle that make them toxic or distasteful to predators. Some species may also prey on tunicates. Tylodinid False Limpets are eaten by fish and other sea slug species. Some species host epibionts on their shells. Otherwise, there are no documented commensal, parasitic or symbiotic relationships between False Limpets and other species.