Dall’s Chromodorid, Chromolaichma dalli

Dall’s Chromodorid, Chromolaichma dalli. Underwater photographs taken in Zihuatanejo Bay, Guerrero, March 2019. Photographs courtesy of Ron Woheau, Zihuatanejo.

Dall’s Chromodorid, Chromolaichma dalli. Underwater photographs taken in Zihuatanejo Bay, Guerrero, March 2022. Photographs courtesy of Ron Woheau, Zihuatanejo.

Phylogeny:  Dall’s Chromodorid, Chromolaichma dalli (Bergh, 1879), is a member of the Chromodorididae Family of Nudibranchs. The genus Chromolaichma is one of sixteen genera in that family, and it is comprised of four species. In Mexico this species is known as chromodórido de Dall. This species was named in honor of William Healy Dall. Dall was primarily recognized as a malacologist, but he also made many important contributions to the fields of vertebrate biology, paleontology, cartography, ornithology, and anthropology. Much of his work took place in Alaska. Dall was one of the founders of the National Geographic Society. This species and many other species and geographic features are named in his honor.

Morphology:  Dall’s Chromodorid has an elongated oval profile with a long tapering tail. They are white to beige or gray in color, with small black, red, brown, or greenish spots on the dorsal surface. Larger animals have more numerous smaller black spots and are gray around the center of the dorsum. Smaller animals have larger but fewer orange-red spots. Their margin has an orange tip and the gills and rhinophores are tipped in a darker orange or light red color. They reach a maximum of 4.4 cm (1.75 inches) in length.

Habitat and Distribution:  Dall’s Chromodorid is found on and under rocks. They reside intertidally and can be found at depths up to 18 m (59 feet). In Mexican waters Dall’s Choromodorid is a resident of all waters of the Pacific, including throughout the Sea of Cortez, with the exception that they are absent from north of Guerrero Negro, Baja California.

Diet:  Dall’s Chromodorids are spongivores and feed primarily on the common marine sponge Hyrtios erecta.

Predators: Dall’s Chromodorids are preyed upon by other nudibranchs, crabs, polychaetes, and sea stars. Other potential predators are deterred by this species’ ability to secrete chemical defenses that make it taste bad or even toxic. Dall’s Chromodorids obtain this toxin from the sponges that they eat.

Reproduction:  Dall’s Chromodorids are simultaneous hermaphrodites. They reproduce sexually by hypodermic insemination. This occurs when both mating partners dart their penis toward each other to induce one to act as a male and the other as the female. The victorious one to penetrate the body wall is the dominant male. The eggs are laid as a mass on the bottom stratum. The eggs hatch into veliger larva and later metamorphose into adults.

Ecosystem Interactions: Information regarding interspecies relationships for Dall’s Chromodorids with other components of the ecosystem has not been documented.

Human Interactions: Dall’s Chromodorids have no direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms:  Chromodoris banksi, Chromodoris dalli, Chromodoris sonora, Felimida dalli and Glossodoris dalli.