Spotted Nudibranch, Reticulated Chromodorid

Goniobranchus reticulatus is one of the most visually striking dorid nudibranchs in the tropical Indo-Pacific. Divers know it as the Spotted Nudibranch or Reticulated Chromodorid. French naturalists Quoy and Gaimard first described this species in 1832 from specimens collected at Tongatapu during the Voyage de la corvette l’Astrolabe. Since then, researchers have recorded it throughout the Indo-West Pacific — including the macro diving reefs of Romblon, Philippines.

Appearance and Identification

Goniobranchus reticulatus displays a white to cream mantle with a distinctive red-brown reticulate (net-like) pattern. This pattern gives the species its common name. The mantle edge is narrow and white. The foot carries a yellow border, and the labial tentacles end in yellow tips — both details noted in the original 1832 description. The body reaches up to 100 mm in length, though most individuals our guides find in Romblon measure considerably smaller.

Identification requires care. Goniobranchus reticulatus belongs to the Goniobranchus tinctorius colour group — a complex of at least seven closely related species. Experts now believe that many historical records attributed to G. reticulatus actually belong to distinct species. This makes it a scientifically valuable animal to photograph and document for our Marine Life Encyclopedia.

Behaviour and Biology

Like all Chromodorididae, Goniobranchus reticulatus preys exclusively on sponges. It crawls slowly across reef substrate in search of specific sponge species. The animal is hermaphroditic — it carries both male and female organs at the same time. This adaptation boosts reproductive success in a species that rarely encounters others on the reef. Furthermore, the species lays eggs in a spiral ribbon, a behaviour typical of dorid nudibranchs.

Diving with Goniobranchus reticulatus in Romblon

Romblon’s macro reefs offer excellent habitat for Goniobranchus reticulatus. Our guides regularly spot it on sponge-encrusted reef walls and rubble slopes at 5 to 25 metres depth. Additionally, this species appears at several of our dedicated macro photography diving sites around Alad Island. Our SDI/TDI trained guides know exactly how to find and position nudibranchs for underwater photographers and videographers. For further reading, visit the WoRMS species page or the iNaturalist taxon page.