Cliopsis krohnii

Cliopsis krohnii Troschel, 1854

Cliopsis krohnii @ Lake Worth Lagoon, Florida, USA 2-10-2011 by Anne DuPont
Class: Gastropoda  Cuvier, 1797
Subclass:  Heterobranchia  J.E. Gray, 1840
Clade: Euthyneura  Spengel, 1881
Clade: Euopisthobranchia  Jörger et al., 2010
Clade: Gymnosomata  de Blainville, 1824
Superfamily: Clionoidea  Rafinesque, 1815
Family: Clionidae  Rafinesque, 1815
Genus: Cliopsis  Troschel, 1854
Species: Cliopsis krohnii Troschel, 1854

Taxonomic note: Marine Species Identification Portal recognizes three morphs:


  • Clio mediterranea Gegenbaur, 1855
  • Clionopsis krohnii (Troschel, 1854)
  • Clionopsis microcephalus Tesch, 1903
  • Clionopsis modesta Pelseneer, 1887
  • Cliopsis grandis Boas, 1886
  • Cliopsis krohnii Troschel, 1854
  • Cliopsis modesta Pelseneer, 1887
  • Pneumodermon peronii auct. non Lamarck, 1819
  • Pneumodermon diaphanum Guerin, 1844
  • Trichocyclus mediterranea (Gegenbaur, 1855)

Cliopsis krohnii has a relatively large (up to 40mm), globular (more elongate in juveniles), soft, gelatinous body, with a clearly visible visceral core. The body is translucent in mature specimens, while in younger specimens may be tinted in yellow, light brown, light blue or gray. There is a rose tinge in the head area. It has two rounded fins placed very far forward, near the head. The head is small with highly developed nuchal tentacles without suctors. The terminal gill is located in the posterior side of the body and has four radiating crests connecting to an hexagonal crest surrounding the mucronate body apex. The foot is small and consists of three small median lobes visible between the wings. The mouth has an elaborate foregut, with a proboscis that can extend to two times its body length, chitinous hooks (with the hook sacs containing about 60 hooks) and cutting radular teeth. It lacks a shell but on its early embryonic stage.

As all gymnosomates, Cliopsis krohnii is a highly specialised carnivore predator which feeds on the phytoplankton feeding thecosomate pteropods of the genus Corolla sp. These Corolla catch their food with the aid of an enormous mucuous net (up to 2 meters in diameter) they cast out in front of them. When Cliopsis krohnii senses one of these feeding nets, it stops swimming and begins dragging the net in until Corolla is close enough for Cliopsis‘s long proboscis to reach out and cut the columellar muscle, which attaches Corolla to its shell (Rudman in Sea Slug Forum, 2010), then grasping its victim with the chitinous hooks. Cliopsis can eat animals three times its own size. It spends its whole life amidst plankton. The fins are used for swimming and they can propel the animal quite quickly. Like other gymnosomates it does not regulate buoyancy with ionic balance nor specialised buoyancy structures (Wrobel & Mills, 1998). 


  • Cliopsis. From Greek “Kleio”, Ocean’s daughter and sister of Beroe + “-opsis”, “similar to” or “shaped like”.
  • Krohni. In honor of Dr. August David Krohn, (1803-1891), Russian zoologyst of German origin, he was a pionneer of marine biology and exchanged correspondence with Charles Darwin. He wrote about tunicates and also wrote essential chaetognath works in 1844 & 1853.

Cliopsis krohnii is found in all temperate and tropical seas where it is pelagic and lives amidst plankton at depths down to 1,500 m. (Wrobel & Mills, 1998). It has been found in the Pacific, in the temperate waters north of Southern California (Wrobel & Mills, 1998), also in Caribbean (OBIS, 2016), and in saltwater lagoons in Florida, USA (DuPont A., 2/10/2011, pers. comm.). In the Mediterranean is relatively abundant in the Tyrrhenian Sea and in the Ionian Sea, where it can be found near the coasts of Italy and Tunisia. Scarce in other Mediterranean locations (Riedl, R., 1986).

Known georeferenced records of the species: Cliopsis krohnii (z-200).
: GROC 2010-2011 : VIMAR
: Enric Madrenas : Manuel Ballesteros.
: João Pedro Silva : M@re Nostrum
: Bernard Picton : Other sources
: GBIF.ORG : Marine Regions


        Western Mediterranean:1 Stars
        Eastern Mediterranean:1 Stars
        Atlantic Ocean:2 Stars
This chart displays the observation probability for Cliopsis krohnii
based on our own records.

More pictures


Bibliography based on the works by Steve Long, 2006. Bibliography of Opisthobranchia 1554-2000 and Gary McDonald, 2009. Bibliographia Nudibranchia, with later updates from other resources.

Further reading

Cite this article as:

Pontes, Miquel, Manuel Ballesteros, Enric Madrenas et al. (2012-2017) "Cliopsis krohnii" in OPK-Opistobranquis, Published: 26/11/2016, Accessed: 25/09/2017 at (

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