''Berthellina citrina'', the orange gumdrop, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

sea slug Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time ...

in the family

Pleurobranchidae The Pleurobranchidae are a taxonomic family of sea slugs, marine gastropod molluscs in the clade Pleurobranchomorpha. Characteristics Species in the family Pleurobranchidae have a prominent mantle and an internal shell that becomes re ...

. It is found in rock pools in the intertidal zone and in shallow water in the tropical and subtropical Indo-Pacific region.

Description

''Berthellina citrina'' grows to a maximum length of about and has a broadly ovate body. It varies in colour from a translucent pale yellow to a brick red. The head bears a triangular oral veil with a

ventral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

groove, and a pair of

rhinophore A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea ha ...

s rolled into tubes. The surface of the mantle is studded with small white glands which produce a distasteful whitish secretion. The remnants of the shell are embedded in the mantle and the gut is visible through the overlying tissues. There is a single

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

located in a gap between the mantle and the foot on the right-hand side, with around twenty pectinate lamellae on each side.

Distribution and habitat

''Berthellina citrina'' is a common species found throughout the tropical and subtropical Indo-Pacific, and as far south as New Zealand. As well as being found in rock pools, it occurs on

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...

s and among boulders in the shallow subtidal zone, and down to a maximum depth of . It is nocturnal and hides in crevices and under rocks during the day.

Ecology

Sea slugs in this family mostly feed on

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

s, and ''Berthellina citrina'' is no exception. In

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

, however, it has been observed feeding on the corals '' Tubastrea coccinea'', '' Leptastrea'' sp. and '' Porites lobata'', and it also consumes detritus. The glandular secretion is released when the mantle surface is stimulated and is acidic, containing chlorine and

sulphate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...

ions. It is used as a defence against predators, and in laboratory experiments repelled sea anemones,

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

, and

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

s. Sea slugs in the Pleurobranchidae are hermaphrodites. The eggs are laid in an orange spiral jelly-like egg ribbon.

References

{{Taxonbar, from=Q5057929 Pleurobranchidae Molluscs of the Indian Ocean Molluscs of the Pacific Ocean Gastropods described in 1828 Taxa named by Eduard Rüppell Taxa named by Friedrich Sigismund Leuckart