Chocolate Mango Nudibranch

Reticulidia halgerda

Reticulidia halgerda is a distinctive sea slug that can reach a maximum length of 7.0 cm. It is characterized by its smooth, reticulate ridges on the notum, which sets it apart from similar species in the Phyllidia and Phyllidiopsis genera that possess tuberculate ridges and spiculose tubercles. Unlike Phyllidia ocellata and its relatives, which have yellow-capped tubercles, Reticulidia halgerda lacks these features, making it easier to identify in the field. Additionally, it does not have the broad bluish white border found in Reticulidia fungia, further aiding in its identification during dives. This species is found in the Indo-West Pacific region, spanning from East Australia to Taiwan, and including locations such as the Philippines, Indonesia, the Marshall Islands, and Fiji. It typically inhabits benthic environments and is often encountered at depths shallower than 40 meters. Divers may observe this nudibranch resting on coral reefs or rocky substrates, where it blends into its surroundings. As a simultaneous hermaphrodite, Reticulidia halgerda engages in unique mating behaviors, where individuals will dart their penises toward each other, and the dominant individual will act as the male. Eggs are laid on substrates and develop into planktonic larvae before maturing into adults. Encountering this nudibranch can be a highlight of a dive, as its unique appearance and behavior add to the richness of the underwater experience. The conservation status of this species has not been evaluated by the IUCN.