Cliopsis krohni Troschel, 1854 morpha krohni Troschel, 1854

Overview

This is a medium sized naked pelagic snail, up to 2.4 cm long, with a completely transparent body and the visceral organs are seen through the body wall. The body is oval shaped,balloon-like and the posterior gill is ring-shaped. It is a carnivorous species, living in all oceans in the upper water layers.

Taxonomic Description

Posterior gill present, lateral gill absent. The posterior gill is hexagonal with four rays without fringes. The visceral mass is yellowish-brown, and fills up almost the whole body. When the specimens are not yet full grown, the visceral mass nearly reaches the body pole, but then it does not fill up the entire body. The body integument is slightly coloured or colourless and semi-transparent. The posterior tentacles are retractile, the anterior ones are very small (Cliopsis k. krohni drawing). There are no acetabuliferous arms or buccal cones. The proboscis, when evaginated, is twice as long as the body or even longer. The digestive tube in the proboscis may reach a length of 110 mm. The length of the oesophagus does not permit the buccal organs to become evaginated like the proboscis, they always stay at its basis. A median footlobe is lacking, but a well developed median tubercle with longitudinal grooves is present. The Cliopsis k. krohni radula formula varies between 6-1-6 and 4-1-4. The median plates are tricuspoid. There are about 20 transverse rows of teeth. The first lateral teeth differ from the other laterals by a denticle at the medial side in the middle of the head cusp. The hook sacs are shallow with about 40 to 60 hooks. The egg mass is a round gelatinous mass about 8 mm in diameter.
Body length up to 24 mm.

Juveniles

The larval form of this morph is described probably as Trichocyclus mediterraneus. The caudal ciliary larval-band persists in sexually mature specimens.

Reproduction

This species is a protandric hermaphrodite.

Ecology

This species is a carnivore.

Distribution

This species is represented by three morphs, but their discrimination is too uncertain to give valuable maps for the three morphs separately. The common sympatry of the morphs should be mentioned. In the W Mediterranean the half-full-growns (morpha krohni) animals are more common than elsewhere. This species is found in all oceans between 50°N and 50°S and in the Mediterranean. Its abundance is higher in offshore areas than in the centres of the oceans. Penetration into the Red Sea, Arabian Sea and Bay of Bengal, and the Caribbean, is not known, while avoidance of cold influences in the south is evident. Central water masses seem to be avoided too. See the Cliopsis k. krohni map.

Types

Cliopsis krohni Troschel, 1854: 222, pl. 10, figs. 1-12.
Type: From the original description it may be concluded that only one specimen was mentioned.
Type locality: Messina, Coll.:? Troschel.

Kingdom Animalia
Phylum Mollusca
Class Gastropoda
Subclass Euthyneura
Order Gymnosomata
Suborder Gymnosomata
Family Cliopsidae
Genus Cliopsis
Species Cliopsis krohni
Morpha krohni

Status in World Register of Marine Species

Not included in WoRMS database

Scientific synonyms and common names

Cliopsis krohni Troschel, 1854 morpha krohni Troschel, 1854

Synonyms

Pneumodermon diaphanum? Guérin, 1844: 11
Cliopsis krohnii n. sp. Troschel, 1854: 222
Clio mediterranea n. sp. Gegenbaur, 1855b: 68
Trichocyclus mediterraneus Costa, 1869: 46
Clionopsis krohnii Costa, 1873: 25
Clionopsis krohni Pelseneer, 1885: 500
Cliopsis krohni Massy, 1917: 236
Cliopsis var.I and II :? n. var. Pruvot-Fol, 1924a: 13
Cliopsis krohni morpha krohni Van der Spoel, 1972a: 78

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Bianco, S. Lo, 1904. Pelagische Tiefseefischerei der 'Maya' in der Umgebung von Capri. In: Beitrege zur Kenntnis des Meeres und seiner Bewohner. Jena (G. Fischer Verlag): i-vi, 1-91, 179 figs, 1 map, 42 pls.

Boas, J. E. V., 1886a. Bidrag til Pteropodernes. Morfologi of Systematik samt til Kundskaben om deres geografiske Udbredelse- Spolia Atlantica- Vidensk. Selsk. Skr. (6 Raekke) naturv. math. IV (1): 1-231.

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Costa, A., 1869. Osservazioni su taluni pteropodi del Mediterraneo. Ann. Museo Zool. R. Univ. Napoli 5: 44-46, pl. 1.

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Guérin-Ménéville, F. E., 1844. Iconographie du règne animal de G. Cuvier (Mollusques): 1-64, pls. 1-38 (in separate vol.) Bailliere Paris and London.

Massy, A. L., 1917. The gymnosomatous Pteropoda of the coast of Ireland. Sci. Proc. R. Dublin Soc. (NS) 15(12): 223-224, 1 tab., 6 figs, pl. 8.

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Pafort-van Iersel, G. J. S., 1985a. Contributions to pelagic zoogeography of the mid North Atlantic Ocean, 1. Distribution of pteropods, heteropods and silver hatchetfishes. In: G. J. S. Pafort-van Iersel. A contribution to pelagic zoogeography of the mid North Atlantic Ocean (7th paper) (Thesis Univ. van Amsterdam): 1-45, 5 tabs, 4 figs, 27 append.

Pelseneer, P., 1885. The cephalic appendages of the gymnosomatous Pteropoda, and especially of Clione Quart. J. Microsc. (ns)25(5): 491-509, pl. 35.

Pruvot-Fol, A., 1924a. Étude de quelques gymnosomes méditerranéens des pêches de 'l'Orvet' en 1921 et 1922. Arch. Zool. Exp. Gén. 62(6): 345-400, 32 figs, pls 15-16.

Pruvot-Fol, A., 1926. Mollusques ptéropodes gymnosomes provenant des campagnes du Prince Albert Ier de Monaco. Résult. Camp. Sci. accompl. sur son yacht par Albert Ier 70: 1-60, 3 pls.

Pruvot-Fol, A., 1932. Note sur quelques gimnosomes de provenances diverses et diagnose d'un genre nouveau Arch. Zool. expér. gén. 74 (vol. jub.): 507-529, 18 figs, pl. 3.

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Pruvot-Fol, A., 1942. Les gymnosomes.I . Dana Rep. 4 (20): 1-54, 77 figs.

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Spoel, S. van der, 1973e. Pneumodermopsis teschi n. sp. and notes on some other Pteropoda of the "Thor Expeditions 1903-1910" (Gastropoda). Bull. zool. Mus. Univ. Amst. 3 (9): 53-64.

Spoel, S. van der, 1976c. Pseudothecosomata, Gymnosomata and Heteropoda. Bohn, Scheltema & Holkema, Utrecht. 484 pp. 246 figs.

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