Atagema spongiosa

Atagema spongiosa is an oval and flattened sea slug characterized by its dorsal surface, which is adorned with prominent, rounded tubercles that decrease in size towards the mantle margin. A distinct longitudinal ridge runs centrally along the body between the rhinophores and the gill, flanked by a series of depressions. The dorsal surface is densely covered with caryophyllidia, which are specialized sensory organs. Adult specimens display an opaque grayish-brown body color, while juveniles are translucent gray. The branchial sheath is divided into three lobes, and the gill consists of five tripinnate leaves. Juveniles have less pronounced dorsal tubercles compared to adults, making them distinguishable from mature specimens. This species is found in the tropical Indo-West Pacific Ocean, with a distribution range that includes regions from East Africa to South Korea, as well as Australia, Fiji, and New Caledonia. Atagema spongiosa typically inhabits shallow waters, often under rocks and covered with sponges and other encrusting organisms, at depths ranging from 0 to 8 meters. It is a simultaneous hermaphrodite, engaging in a unique mating behavior where individuals will dart their penises toward each other to determine roles as male or female. Eggs are laid on a substratum, developing into planktonic larvae before maturing into adults. Encounters with Atagema spongiosa during dives can be intriguing, as divers may observe them resting on the substrate, camouflaged among sponges. The species has not been evaluated for conservation status, indicating a lack of specific data regarding its population trends.