Aldisa trimaculata is a species of sea slug, a nudibranch, a shell-less marine gastropod mollusk in the family Cadlinidae. It is a relatively common species found in the intertidal and subtidal zones of the northeastern Pacific Ocean, typically in rocky habitats and kelp forests.
Description & Characteristics
Aldisa trimaculata is a small to medium-sized nudibranch, reaching a maximum size of about 4 cm in length. The body is elongated and cylindrical with a characteristic three-lobed oral veil. The dorsal surface is covered in numerous small, raised tubercles that give it a rough texture. The color of the body is typically a bright orange or red, often with three prominent white spots on the back, giving rise to its common name. These spots are often surrounded by a dark ring. The rhinophores are club-shaped and lamellate, while the cerata are short and cylindrical.
Habitat and Occurrence
Aldisa trimaculata is a common inhabitant of rocky shores and kelp forests along the Pacific coast of North America. It occurs from Alaska to California, and has also been reported from British Columbia. The species is found in a variety of marine zones, including the intertidal, subtidal, and even the deeper sublittoral zone, often in areas with strong currents. This nudibranch is often observed on seaweeds, bryozoans, and other invertebrates.
Taxonomy
Aldisa trimaculata is classified within the phylum Mollusca, class Gastropoda, order Nudibranchia, and family Cadlinidae. The family Cadlinidae is a diverse group of nudibranchs, containing over 100 species worldwide. Many cadlinids are known for their bright coloration and distinctive features, such as their branched cerata.
Feeding
Like other nudibranchs, Aldisa trimaculata is a carnivore. It primarily feeds on hydroids, which are colonial marine animals related to jellyfish. Aldisa trimaculata uses its radula, a ribbon-like structure with rows of teeth, to scrape and ingest the polyps of hydroids. The nudibranch often consumes the nematocysts (stinging cells) of its prey, storing them in its own body. These stolen nematocysts can then be used for defense against predators.
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