About Mexichromis trilineata (A.Adams & Reeve, 1850)
Mexichromis trilineata is a species of nudibranch that typically reaches 7 mm to 15 mm in length. It has an elongate to broadly oval body shape, with the tail extending slightly past the posterior body margin. Its mantle features three yellow longitudinal bands, each outlined in white, and the entire mantle edge is trimmed with a fine white line. Additional yellow patches bordered in white occur around the mantle edge. Defensive mantle glands, arranged in roughly two rows along the mantle edge, appear as pale pink patches. The gills and rhinophores are characteristically violet at the base, transitioning to translucent white with red markings towards the tips. As the species name trilineata indicates, individuals usually have three full longitudinal lines, but variations do occur. In some specimens the lines are broken into a series of shorter segments, while in others the two outer lines are completely absent. Some individuals also have yellow or orange markings on the white lines that outline the bands. This species has been recorded from Sumbawa, Sulawesi and Bali, Indonesia; the Philippines; the South China Sea; and Heron Island, Great Barrier Reef, Queensland, Australia.
