Twinspot Rainbow Dorid, Mexichromis pusilla, a true gem of the tropical Indo-Pacific and 🌊 Red Sea! This exquisite little sea slug, a dorid nudibranch and a member of the Chromodorididae family, is a delight to encounter on our dives.
Growing to a modest length of at least 20 millimetres (about 0.8 inches), this species captivates with its vibrant hues. Its body is typically a delicate pink-orange, framed by a broad, pale yellow band along the edge of its mantle. A key identifying feature, and indeed the origin of its common name, are the two prominent white spots adorning its back, or dorsum. Its striking feathery gills, which form a branched orange "crown" at the back of its body and allow the mollusk to breathe underwater, and its two prominent horn-like rhinophores on its head - acting as crucial chemical sensors for 'smelling' and 'tasting' the water - are both a brilliant orange.
This vibrant palette, often combining white, purple, and orange hues on the mantle and appendages, is more than just pretty; it serves as a crucial warning. Like many nudibranchs, Mexichromis pusilla is aposematic, meaning its bright coloration advertises its toxicity or unpalatability to potential predators, effectively telling them, "I'm not good to eat!"
As with all members of the Chromodorididae family, Mexichromis pusilla has a specialized diet, feeding exclusively on sponges. While its beauty is undeniable, identifying this particular dorid can sometimes be a fun challenge, as it's easily confused with other similarly coloured nudibranchs, such as Verconia varians and Verconia norba. But with a keen eye for its distinctive twin white spots, you'll soon be able to pick out this tiny rainbow slug!
