Thuridilla bayeri or painted sea slug belong to a clade of Sacoglossa, in a family Placobranchidae. Sacoglossan include various marine opisthobranch gastropod mollusks that belong to the clade Heterobra
nchia (EOL 2011; Marshall 1999). Sacoglossans often refer to "sap-sucking sea slugs" as they live by ingesting the algae internel contents (Marshall 1999; Jensen 1992; Gosliner 1995). The majority of this clade have no shell including Thuridilla bayeri. Unique features of the Sacoglossans is the single row of teeth on their radula, which have been adapted for suction feeding (Jensen 1992; Jensen 1997).
Thuridilla bayeri is moderately large in size with a smooth body. As they belong to ophostobranchia, they have undergone detorsion (Marshall 1992; Jensen 1992). Inrolled Rhinophores of T. bayeri is long and with a blunt end. Their body background body colour is black with longitudinal white strips pattern. All specimens collected during samples period have blue spots on the outside of the parapodia. However, bright yellow-orange colour can be observed at the inner margin of the parapodia, the front of the foot, and the tips of the rhinophores (Thompson & Jaklin 1988).
Thuridilla bayeri both day and night, actively crawling on substrates (Marshall 1992). However, they are more common during the low tide between the day. One obvious behaviour of this species is periodically "nodding" the head. This typical behaviour refers to the raising and lowering the anterior section of its foot off the substrate (Marshall 1992). However, the biology of this behaviour is still unknown. Feeding behaviour and diet of T. bayeri is also unknown. Although, many Sacoglossa normally associated with particular algal type (Marshall 1992; Sander-Esser 1984; Marcus 1980), T. bayeri show no association with any alga. Painted sea slug is hermaphroditic and reproduce by copulation (Jensen 1992). They spawn as a tightly coiled orange mass. Their eggs mass are laid against the flat substrate. Larvae hatch as free-swimming veligers (EOL 2011; Jensen 1992).
Underwater footage tracking Thuridilla bayeri clawing on coral substrate at night at Fiji Islands (South Pacific) © 2006-2011 Undersea Productions