Morphology and taxonomy of a new species of otoplanid (Plathelminthes, Rhabditophora, Proseriata) from the Ligurian Sea

A new species, Otoplana oxyspina, sp. nov., collected in the "Otoplanen-Zone" of the Ligurian Sea, is described. Although the specimens show the typical morphologic peculiarities of the subfamily Otoplaninae ("Turbellaria", Proseriata), they nevertheless differ clearly from the species already described. The body length reaches 3.3-4 mm and the anterior end is characterized by the presence of a swelling between the two couples of thick retractile tactile bristles. The rhabdites are grouped into longitudinal rows along the body with the exception of the anterior end. The vitellaries, present on both sides from the anterior end to the pharynx opening, consist of two longitudinal rows. Internally, two longitudinal rows of testes reach the paired germaries located in front of the pharynx. The male copulatory organ consists of a pointed median aculeus (56 mu m long) and 20 spines of different shape and length (36-65 mu m). This new species differs from O. intermedia and O. trunicaspina in its body dimensions, the shorter path of the vitellaries, the reduction of testes, and especially in the characteristics of the male sclerotic apparatus, but it appears more similar to O. bosporana collected on the Black Sea.