Yellow with black spots and blue tips, and among the most requested nudibranchs in the region.
The name here has just become complicated and it is worth getting right. Until 2026 every Pikachu nudibranch was called Thecacera pacifica. In that year three new polycerids were described from Timor-Leste, one of them Thecacera pikachu, and the animal Southeast Asian divers photograph appears to be that species rather than pacifica — which is common in Japan, where the nickname started, and uncommon elsewhere. The two are separable: pacifica is yellow to deep orange-yellow, to about 50 mm, with the extra-branchial processes and tail tip graded from black to sky blue; pikachu is smaller, to about 40 mm, pale orange with regularly arranged black spots including two dotted lines running along the edges of the back. This site follows the newer name, and the caution the describing authors made themselves: some of the most photographed animals in the sea turn out to be undescribed or misidentified.
Both have the shape that makes the animal recognisable — a pair of large finger-like processes flanking the gill, and rhinophores held in sheaths. Polycerids graze bryozoans, and orange bryozoan colonies have been suggested as the food here, though the association has not been confirmed. Egg masses are laid as a spiral ribbon. Recorded from about 1 to 30 m in the Philippines, Indonesia, Malaysia, China, Japan and Timor-Leste. There is a Gulf of Mexico record for pacifica attributed to shipping.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
