Cliopsis krohnii

Cliopsis krohnii Troschel, 1854

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

Synonyms

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

Description
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.

Biology
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). 

Etymology

• Cliopsis. From Greek “Kleio”, Ocean’s daughter and sister of Beroe + “-opsis”, “similar to” or “shaped like”.
• Krohnii. 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.

Distribution
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
Sources:
: OBIS : GROC 2010-2011 : Enric Madrenas : João Pedro Silva : Bernard Picton : GBIF.ORG	: OPK : VIMAR : Manuel Ballesteros. : M@re Nostrum : Altres fonts : Marine Regions

Abundance

Western Mediterranean:	★☆☆☆☆
Eastern Mediterranean:	★☆☆☆☆
Atlantic Ocean:	★★☆☆☆