Risbecia versicolor is a species of sea slug, a dorid nudibranch, belonging to the family Chromodorididae. It is recognized for its distinctive and highly variable color patterns, from which its specific epithet "versicolor" (Latin for "variously colored") is derived.
Classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Order: Nudibranchia
Suborder: Doridina
Superfamily: Chromodoridoidea
Family: Chromodorididae
Genus: Risbecia
Species: R. versicolor
Description
Risbecia versicolor typically exhibits an elongated, relatively high-bodied form, capable of growing up to 6 centimeters (2.4 inches) in length. The body is usually a base color of creamy white or pale yellow, strikingly ornamented with longitudinal lines or dashes that run along the mantle. These markings vary considerably in color, ranging from dark brown to black or purplish, and can be continuous, broken, or irregular. The mantle edge often features a thin, undulating border line, frequently in shades of blue or purple. The two prominent rhinophores (sensory tentacles) and the posterior feathery gills (branchial plume) are usually a vivid contrasting color, such as bright yellow, orange, or reddish, sometimes with white tips or bases. The significant individual variation in coloration is a defining characteristic of the species.
Distribution and Habitat
This species has a wide geographic distribution across the tropical Indo-Pacific region. Its range extends from the Red Sea and the East African coast throughout the Indian Ocean, reaching the Western Pacific, including countries such as Australia, Indonesia, the Philippines, and Japan.
Risbecia versicolor inhabits coral reefs and rocky substrates, typically found at depths ranging from a few meters to approximately 30 meters. It is frequently observed crawling on or near sponges, which constitute its primary food source.
Ecology
As is common among nudibranchs within the family Chromodorididae,
Risbecia versicolor is a specialist feeder, selectively preying on specific species of sponges. Its conspicuous and often bright coloration is thought to be aposematic, serving as a warning to potential predators that the nudibranch may be unpalatable or toxic, likely due to chemical compounds sequestered from its sponge diet. It employs its rhinophores to detect chemical cues in the water, aiding in navigation and the location of food and conspecifics.