Domino Nudibranch

Phyllidiella zeylanica

Phyllidiella zeylanica is a distinctive sea slug characterized by its numerous, very tuberculate pink ridges that curve to connect at both ends, although these may be interrupted. Its pale foot sole and dark triangular oral tentacles further distinguish it from similar species. Unlike Phyllidiella pustulosa, which lacks ridges, and Phyllidiella rosans, which has smoother, rounded ridges, Phyllidiella zeylanica's pronounced tuberculate features are a key identifier. This species is typically found in the tropical Indian Ocean, having been described from Sri Lanka and reported from eastern Africa to Java, thriving in benthic environments. It is commonly encountered at depths shallower than 40 meters, with most sightings occurring around 20 meters or less. As a simultaneous hermaphrodite, Phyllidiella zeylanica engages in a unique mating behavior where individuals extend their bodies and use their penises to stimulate each other, determining which will act as the male. Eggs are deposited on substrates, developing into planktonic larvae before maturing into adults. Encounters with this nudibranch during dives can be intriguing, as divers may observe its slow movements across the substrate, often blending with the surrounding environment. The conservation status of Phyllidiella zeylanica has not been evaluated by the IUCN, indicating that its population status is currently unknown, and it is recorded in various locations across its habitat, suggesting it may be relatively common.