Chromodoris willani Nudibranch – Anilao

This vibrant blue creature is Chromodoris willani, also known as Willan’s chromodoris, a species of shell-less marine gastropod mollusk commonly known as a nudibranch.
These are dorid nudibranchs known for their stunning blue coloration, often with black longitudinal lines. A defining feature that helps distinguish them from similar species is the presence of numerous white speckles on their dark rhinophores (scent-sensing tentacles) and gills. These sea slugs are carnivorous and primarily feed on sponges. Their bright colors serve as aposematic signals, warning potential predators that they are unpalatable or toxic. This image was taken off Anilao near Batangas in the Philippines.