Cliopsis krohnii Troschel, 1854. is the only species in Cliopsis, a genus of sea angels belonging to the family Cliopsidae

Cliopsidae

Cliopsidae, common name sea angels, are a taxonomic family of small free-swimming sea slugs, pelagic marine opisthobranch gastropod mollusks in the order Opisthobranchia....

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The Marine Species Identification Portal recognizes three morphs

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

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• Cliopsis krohni Troschel, 1854 morpha grandis Boas, 1886; body length : 40 mm
• Cliopsis krohni Troschel, 1854 morpha krohni Troschel, 1854; body length : 24 mm
• Cliopsis krohni Troschel, 1854 morpha modesta (Pelseneer, 1887); body length : 3 mm

Distribution

Cliopsis krohnii is a small free-swimming sea slug

Slug

Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...

, found in all warm and temperate seas where it is pelagic and lives amidst plankton

Plankton

Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

 as deep as 1,500 m.

Description

Cliopsis krohnii has a somewhat long, flabby, gelatinous body with a bluish aspect. The head is rather small with the nuchal tentacles much developed. The posterior gill possesses four distinct radiating hexagonal crests lacking foldings or fringes. The foot is reduced to three small median lobes.The anterior lobes of the foot show a posterior right angle. The posterior end of the foot has a folded tubercle that is not divided by longitudinal wrinkle in the middle. The distal extremities of the fins are rounded. It lacks a shell except during its early embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

nic stage. The small lateral winglike flaps (parapoda

Parapodium

Parapodia , singular parapodium, are paired, un-jointed lateral outgrowths from the bodies of two different invertebrate groups, which are primarily marine in habitat...

) are used in a slow swimming mode.

This species is a highly specialized predator. It preys on pseudothecosomes, such as Corolla. On making contact with the wide mucous web of its victim, it grabs the victim with a long proboscis

Proboscis

A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...

 (up to twice its own length), chitin

Chitin

Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...

ous hooks (with the hook sacs containing about 60 hooks) and cutting radula

Radula

The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...

r teeth. They can eat victims three times their own size.

Further reading

• Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca, in: Costello, M.J. et al. (Ed.) (2001). European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50: pp. 180–213
• Rolán, E. (2005). Malacological fauna from the Cape Verde Archipelago: 1. Polyplacophora and Gastropoda. ConchBooks: Hackenheim, Germany. ISBN 3-325319-73-2. 455 pp.
• Willan, R. (2009). Opisthobranchia (Mollusca). In: Gordon, D. (Ed.) (2009). New Zealand Inventory of Biodiversity. Volume One: Kingdom Animalia. 584 pp