Tambja morosa

To spot and photograph *Tambja morosa*, focus your search on steep drop-offs, shaded reef ledges, cavern entrances, and vertical coral pinnacles where current delivers nutrients to sessile bryozoan colonies. Mastering precise, motionless neutral buoyancy is essential; maintain a non-contact profile above the reef using gentle sculling or frog kicks to prevent disturbing the delicate substrate or kicking up silt. Macro photographers should equip a dedicated 60mm to 105mm macro lens coupled with dual strobes or strong video lights. Because the deep navy-black body absorbs substantial light, proper strobe positioning with moderate power output is critical to illuminate the rich blue highlights without blowing out the highlights on surrounding pale substrates. Avoid touching or prodding the nudibranch, as mechanical disturbance can cause it to retract its prominent gill plumes and disrupt its natural foraging behaviour.

Because *Tambja morosa* is a resident benthic invertebrate with stable year-round populations across the Indo-Pacific, encounters depend largely on regional diving seasons. In Indonesia, dive liveaboards visiting Komodo National Park find optimal sea conditions and stunning visibility between April and November, while the calmest seas in Raja Ampat occur from October to April. In the Philippines, the macro havens of Anilao and Dumaguete offer productive critter diving year-round, though the peak window with dry weather and excellent water clarity spans from November to May. In Australia, the tropical waters of the northern Great Barrier Reef and the Coral Sea are best dived between June and December, when trade winds ease and visibility peaks across outer reef walls. In the Red Sea, warm waters and tranquil conditions between May and October provide ideal dive profiles for scanning shaded vertical drop-offs.

*Tambja morosa* inhabits thriving coral reef ecosystems across the tropical and subtropical Indo-Pacific basin, with a range extending from the Red Sea and the eastern coast of Africa across to Indonesia, the Philippines, Papua New Guinea, and the Great Barrier Reef in Australia. It is primarily a reef-dwelling species found at depths ranging from shallow sub-tidal flats at 2 metres down to deep vertical walls exceeding 35 metres. The animal thrives in areas subjected to moderate-to-strong water movement, where nutrient-rich currents foster the growth of encrusting and branching bryozoans. Divers frequently encounter this nudibranch crawling over shaded rocky undercuts, cavern roofs, sea-fan bases, reef pinnacles, and rubble-strewn slopes flanking steep drop-offs, where it finds both shelter from direct midday sunlight and an abundance of food.

*Tambja morosa* is a stenophagous carnivore that feeds almost exclusively on sessile arborescent and encrusting bryozoans (moss animals). Its primary prey consists of colonial bryozoan species, particularly those within the genera *Bugula*, *Sessibugula*, and *Bugulella*. Using its specialized, chitinous radula (a toothed tongue-like structure), the nudibranch rasps away the individual zooids from the rigid bryozoan matrix, ingesting both the soft animal tissues and associated organic material. Feeding occurs continuously throughout the day and night as the sea slug grazes across prey colonies. Interestingly, by consuming these specific bryozoans, *Tambja morosa* assimilates bioactive alkaloids—including tambjamines—which it sequesters within its own mantle tissue, rendering itself unpalatable and chemically defended against predatory reef fish and crustaceans.