Pneumoderma mediterraneum (Van Beneden, 1838b)
Overview
This is a relatively large naked pelagic snail, about 2 cm long. It is oval, with a slightly transparent, and usually pigmented skin. The wings are well developed, the posterior footlobe is long. The buccal mass shows two lateral arms, each with up to 7 suckers, the median suckers are larger than the others. It lives in the warm waters of all oceans in the upper water layers and is never abundant (Pneumoderma mediterraneum).
Taxonomic Description
The rather long body bears a posterior gill with well developed long fringes and a short lateral gill with fringes. The posterior footlobe is longer than in Pneumoderma atlanticum. The long sucker arms each has 6-7 suckers of which the central four are the largest. In specimens of 17 mm they are 2 mm across. The hook sacs are long and show numerous (40) fine hooks. These hooks are placed on a spirally coiled appendage. The radula formula is usually 7-0-7, sometimes 6-0-6 or 6-1-6.
Body length 20 mm.
Juveniles
A special description is not available.
Reproduction
This species is a protandric hermaphrodite.
Ecology
This species is carnivorous.
Distribution
A reasonable number of records is known for this species. It shows a discontinuous distribution in warmer waters. Compared with P. atlanticum subsp. atlanticum, the only difference is that the present species does not penetrate the Pacific Ocean, see the Pneumoderma mediterraneum map.
Types
Pneumoderma mediterraneum Van Beneden, 1838: 13, pl. 3, figs. 1-2.
Types are not in IRSN or other collections studied by Van Beneden.
Type locality: off Nice. Coll.: Verany (or Van Beneden).
Pneumodermon macrocotylum Boas, 1886: 153 (syn. of Pneumoderma mediterraneum Van Beneden). Lectotype: ZMUC (formally in the college of Veterinary College at Copenhagen) Paralectotypes: ZMUC, 7 specimens.
Type locality: Number 45 in list Boas (1886) restricted: 20°14'S 1°4'W. Coll.: Andréa, 1862. The specimens given in the list by Boas (1886) with the indication"Neapel, 43, 44, 46, 47, 48, 49", are not considered to be paratypes. The specimen from Messina is lost.
Original type description of Pneumodermon macrocotylum Boas, 1886: Under ovenstaaende Navn sammenfatter jeg et Antal Pneumodermer fra forskjellige Have, som stemmer med hinanden deri, at Armene er meget korte og langs Randen forsynede hver med 7 (eller maaske undertiden kun 6) Sugeskaale, der sidder i to alternerende Rækker (ialfald paa halvt udkrængede Exemplarer). Af disse 7 Sugeskaale er de 4 midterste omtrent lige store og meget slore; den inderste - som undertiden synes at kunne mangle - er sædvanlig mindre, undertiden meget lille eller rudimentær; de to yderste (distale) ligeledes mindre, undertiden særdeies smaa. Sugeskaalenes Form er som en Inddamp–ningsskaal uden Tud. Jeg har fundet Sugeskaalenes Forhold saa ligt - om end ikke identisk - hos de foreliggende exemplarer, at jeg ikke tvivler om, at de alle tilhører samme Art, eller om flere, da ialfald særdeles nærstaaende. Farven er paa de foreliggende Spiritus-Exemplarer lidt forskjellig, nogle er blegere, andre mørkere. - Det største Exemplar maalte 17 mm (uden de udkrængede Dele; det er udspilet, har nylig ædt); de store Sugeskaale maalte hver næsten 2mm. - Arten er tagen i Atlanterhavet (incl. Mliddelhavet), i det Indiske og Kinesiske Hav.