''Thuridilla moebii'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

sacoglossa Sacoglossa are a superorder of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia known as sacoglossans. There are 284 valid species recognized within this superorder. Sacoglossans live by ingestin ...

sea slug Sea slug is a common name for some Marine biology, marine invertebrates with varying levels of resemblance to terrestrial Slug, slugs. Most creatures known as sea slugs are gastropods, i.e. they are Sea snail, sea snails (marine gastropod moll ...

, a shell-less marine

opisthobranch Opisthobranchs () is a now informal name for a large and diverse group of specialized complex gastropods which used to be united in the subclass Opisthobranchia. That taxon is no longer considered to represent a monophyletic grouping. Euopistho ...

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusc in the family

Plakobranchidae Plakobranchidae is a family (biology), family of sea slugs, marine (ocean), marine opisthobranch gastropod mollusks in the superfamily Plakobranchoidea. They superficially resemble nudibranchs but they are sacoglossans, members of the clade Sacog ...

. It is found in shallow water in the tropical west and central Indo-Pacific region.

Description

''Thuridilla moebii'' is a small, slender slug, growing to a maximum length of about . On either side of the body there are

parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; : parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed late ...

which fold up and over the back, joining at the top, and forming a sheath from which the head projects at the front. The basic colour is translucent white, often tinted with bluish-green, or even pale blue. Along the upper surface is a bold longitudinal, zigzag band of contrasting colour, usually deep orange above and blackish below (but sometimes all black), uniformly speckled with white dots. The head is white and bears a pair of large, rolled

rhinophore A rhinophore is one of a pair of Chemoreceptor, chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, Marine (ocean), marine gastropod opisthobranch mollusks suc ...

s, which extend forward, the tips of which match the colouring of the band on the body. The front edge of the foot has a similar colouring.

Distribution and habitat

''Thuridilla moebii'' is found in shallow water in the tropical and subtropical Indo-Pacific region, its range extending from South Africa to Western Australia, including

Mayotte Mayotte ( ; , ; , ; , ), officially the Department of Mayotte (), is an Overseas France, overseas Overseas departments and regions of France, department and region and single territorial collectivity of France. It is one of the Overseas departm ...

, the

Comoro Islands The Comoro Islands are a group of volcanic islands in the Mozambique Channel, an arm of the Indian Ocean lying between Madagascar and the African mainland. Three of the islands form the Union of the Comoros, a sovereign nation, while Mayotte bel ...

Réunion Réunion (; ; ; known as before 1848) is an island in the Indian Ocean that is an overseas departments and regions of France, overseas department and region of France. Part of the Mascarene Islands, it is located approximately east of the isl ...

and

Mauritius Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Ag ...

. Its habitat includes sandy areas where

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

accumulates, and rocky reefs with scanty coral cover and suitable algal growth.

Ecology

Members of the ''

Thuridilla ''Thuridilla'' is a genus of sacoglossan sea slugs, shell-less marine opisthobranch gastropod mollusks in the family Plakobranchidae.Bouchet, P.; Gofas, S. (2012). Thuridilla Bergh, 1872. Accessed through: World Register of Marine Species at ht ...

'' genus are vegetarians, feeding on algae. ''Thuridilla moebii'' has a saw-edged

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...

which it uses to grate or puncture the cell walls of the algae on which it feeds. The individual sea slug examined when the species was redescribed in 1995 had 23 triangular teeth in a single row on the radula. The teeth are constantly being replaced as they wear down, the discarded teeth falling into a special sac in the mouth where they are retained. The precise diet for this species is not known, but in Réunion it is reported to often be seen on a green alga, the spherical turtle shell (''

Bornetella sphaerica ''Bornetella sphaerica'', commonly known as the spherical turtle shell, is a species of marine alga in the Dasycladaceae family. It is found in the tropical Indo-Pacific region, the type-location being Sorong, Irian Jaya, Indonesia.

''). ''Thuridilla moebii'' is a simultaneous

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

; the penis is located on the head just behind the right rhinophore. When breeding, two individuals entwine in such a way as to bring the right sides of their heads together, and sperm is passed between the pair. Later, each individual lays an orange egg ribbon in the form of a wide spiral, sticking the gelatinous thread to the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

References

{{Taxonbar, from=Q14491679 Plakobranchidae Gastropods described in 1888