''Philinopsis speciosa'', the blue-lined philinopsis, is a species of

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

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 Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the family

Aglajidae Aglajidae is a family of often colorful, medium-sized, sea slugs, marine opisthobranch gastropod mollusks. These are not nudibranchs; instead they are headshield slugs, in the clade Cephalaspidea The order Cephalaspidea, also known as the ...

. It is native to the Indo-Pacific region.

Description

''Philinopsis speciosa'' is a large mollusc, growing to a length of about . It has a well-developed, broad headshield, with a squared front and tapering rear, terminating in an upright tube; the headshield is used for gliding over and burrowing beneath the surface of the sand. Behind the headshield is a body shield which bears two, rounded lobes at the back. On either side of the body are lateral outgrowths known as

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 ...

. The colour of this sea slug is very variable; it is usually brown, dark brown or black, with white, cream, yellow or orange spots, and a thin blue line or streaks around the margin. There is sometimes an additional white or yellow line at the margin, and a pair of longitudinal orangish bands may be present near the midline of the headshield.

Distribution and habitat

''Philinopsis speciosa'' has a widespread distribution in the tropical Indo-Pacific region, its range extending from the east coast of Africa and the

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

to Japan, Hawaii and New Caledonia. It is found on the lower shore and the

subtidal zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

, on sandy and clay bottoms and among

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

, at depths down to about .

Ecology

Like other members of the

, ''Philinopsis speciosa'' is a predator. Its prey consists mostly of other gastropod molluscs. It has no

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 ...

, but has a partially eversible pharynx which can suck up and engulf its prey, swallowing it whole. After digestion of the soft tissues, any shell or indigestible material is regurgitated. ''Philinopsis speciosa'' is a

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 ...

; two or more individuals form a circle or a short chain. The penis is on the right, level with the head, and the female genital opening is on the right side further back. The first individual acts as a female and receives sperm from the second, which acts as both male and female, giving sperm to the first, and receiving sperm from the third. The last slug in the line acts only as a male. The white eggs are wrapped in a thin layer of mucus and this strand is wound around the slug's head in a tangled cylinder. The slug then removes its head from the cylinder and sticks the end of the filament to the substrate.

References

{{Taxonbar, from=Q14087603 Aglajidae Molluscs of the Indian Ocean Molluscs of the Pacific Ocean Gastropods described in 1933 Taxa named by William Harper Pease