Prostheceraeus, Schmarda, 1859

Faubel, A. & Warwick, R. M., 2005, The marine flora and fauna of the Isles of Scilly: Free-living Plathelminthes (‘ Turbellaria’), Journal of Natural History 39 (1), pp. 1-45 : 21-22

Prostheceraeus IJittatus (Montagu 1815) Lang, 1884

( Figure 5 )

Proceros cristatus Quatrefages, 1845: 139 , pl. III: 7.

Eurylepta υittata: Diesing, 1850: 209.

Prostheceraeus cristatus: Schmarda, 1859: 30 .

Material examined

Voucher specimen: site 6, one specimen; site 17: L. A. Harvey and P. C. Chapman, unpublished.

Geographical distribution. NE Atlantic: Ireland (Co. Mayo: Clew Bay, Westport Channel, Blacksod Bay, Co. Galway: Ballynakill Harbour, Co. Kerry: Valentia Harbour); Irish Sea: Ireland (Co. Down (Strangford Lough), Co. Dublin (Dalkey Sound)); Celtic Sea: Ireland (Co. Cork: Lough Hyne), Bristol Channel (South Wales); English Channel: England (Yealm River, Falmouth, Kingsbridge Estuary: Salcombe, Plymouth Sound, Dorset: Lundy Island, Channel Islands), France (Saint-Vaast-la-Hougue, Concarneau); North Sea: Norway (Bergen, FlorØ); Skagerrak: Norway (Brederigen, Mandal), Sweden (Gullmarfjord, Bohuslän, Gasö, Löken); Mediterranean Sea: Gulf of Naples ( Lang 1884; Gamble 1900; Bock 1913; Prudhoe 1982; Faubel 1984).

Remarks

The most comprehensive description of Prostheceraeus υittatus was made by Lang (1884). Later on, more valuable data were given by Bock (1913) and Prudhoe (1985) on the morphology, anatomy and the geographical distribution. The discovery of P. υittatus at site 6 on the Isles of Scilly offers the opportunity to study the anatomical structures again. This re-investigation reveals some new aspects to the anatomy of the species. Eyes are present as follows: cerebral eye clusters arranged in two elongate rows dorsal of the brain, tentacular eyes being less numerous almost exclusively distributed at the tentacular basis and the tentacles in between, and ventral eye clusters abundantly arranged halfway between anterior tip and brain. The relatively short plicate cylindrical pharynx, orientated horizontally in the pharyngeal cavity, is bell-shaped, i.e. the pharynx becomes wider distad. The reproductive apparatus matches that of P. albocinctus Lang, 1884 as presented by Prudhoe (1985: 142, Figure 129B). It is very obvious that the reproductive system of the species of Euryleptidae look anatomically very similar. The same is known for the species of Pseudocerotidae . The male atrium of Prostheceraeus υittatus is strongly provided with muscles and is subdivided into a ciliated outer and inner cavity. The inner one houses the ejaculatory duct which is distally armed with a pointed stylet. The distally tapering stylet is 135 M m long and 74 M m in diameter at its base (m. VS) ( Figure 5 ). At a distance of 72 M m (m. VS) proximad from the base of the stylet, the prostatic duct branches off from the ejaculatory duct. The prostatic vesicle is enclosed in a 12 M m (m. VS) thick muscle wall. The glandular inner lining is smooth; the maximum thickness 76 M m (m. VS). The longitudinal axis is 530 M m (m. VS). Extravesicular glands are not present. The measurements were made from serial sections.

Figures

Figure 5. Prostheceraeus υittatus. Diagrammatic sagittal reconstruction of the male copulatory apparatus. Scale bar: 300 Mm.