Thick-horned Nudibranch

Hermissenda crassicornus

Physical Description

The Thick-horned Nudibranch, scientifically known as Hermissenda crassicornus, showcases a translucent greyish-white body. It features a median band of brilliant cadmium orange between its oral tentacles, passing between the rhinophores and extending to the anterior of the cardiac region. Additionally, opalescent blue lines run dorsally on either oral tentacle, bifurcating proximally, with the inner portion extending between the rhinophores. Outer portions of these blue lines extend dorso-laterally to the tail tip. The nudibranch’s foot bears a narrow, opalescent blue line along its dorsal margin, from the foot corners to the tail tip. Cerata are arranged in 5-11 groups, with reddish-orange tips and a bluish-white longitudinal band on the anterior surface of each ceras. Rhinophores are weakly perfoliate, exhibiting about 10-14 lamellae, and appear opalescent white to very pale blue.

Habitat and Geographical Range

The Thick-horned Nudibranch is commonly found along the eastern Pacific coast. It inhabits various marine environments, including rocky substrates and kelp forests.

What They Eat and How They Breed

These nudibranchs likely feed on small invertebrates and algae. For reproduction, they likely engage in mating behavior, where they exchange sperm. Females then lay eggs, which are often deposited in gelatinous masses on suitable substrates. After hatching, the larvae undergo a pelagic stage before settling on the ocean floor.

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