Janolus incrustans Pola & Gosliner, 2019

ハナサキコヤナギウミウシ Janolus incrustans
Photographed by
bighit2000 Manabu Kakegawa
Gerombong, Tulamben, Pulau Bali, Indonesia
Water temperature


This species has been found under coral rubble and in Halimeda beds in 2–10 m depth. It has not been found in association with a specific prey source.
Living specimens reaching 18 mm in length (Gosliner et al., 2015). Body broadest anteriorly, tapering to elongate posterior end of the foot extending well beyond notum. Rhinophores elongate without distinct lamellae, covered by series of irregular tubercles over most of length. Well-developed caruncle present between rhinophores consisting of series of irregular papillae. Eyes, appearing as two small black dots immediately behind rhinophores. Swollen cardiac area located near middle of notum, immediately posterior to rhinophores. Pair of short, digitiform oral tentacles extending from either side of head. Cerata elongate, very globose apically, and densely covered with numerous white papillae. Each ceras with pointed tubercle apically. Cerata distributed over entire body in 11–13 rows, with 2–3 cerata per row. Digestive gland inserting into most of cerata at base. Digestive gland duct very narrow and elongate, extending to tip of each ceras. Each duct bifurcating in upper half of ceras. Anteriormost cerata also containing extensions of digestive gland. Anus located mid-dorsally near posterior end of notum. Anal glands absent. Gonopore located on right side middle of body.


This species is known only from the Marshall Islands and Indonesia (Gosliner et al., 2015).


This species is named from the Latin incrustans, meaning encrusted, and referring to the opaque white pigment that appears to encrust the body.