Postbursoplana parafibulatasp. nov.: A new flatworm from the Ligurian Sea (Plathelminthes, Rhabditophora, Otoplanidae)

A new species, Postbursoplana parafibulata sp. nov., is described from lower interstitial habitats of the Upper Tuscan sea coast (Ligurian Sea). The specimens display the typical collar-shaped pharynx, perpendicularly positioned, of the subfamily Parotoplaninae (“Turbellaria”, Otoplanidae). The sexually mature animals are 1.2–1.4 mm in length, and appear to belong to the genus Postbursoplana because of the general arrangement of testes and germo-vitellaria, and of the sclerotic apparatus characteristics. Their male copulatory organ consists of 10 spines differentiated in five groups with variable shape and length (52–73 μm). P. parafibulata sp. nov. differs from the already described species above all for the body dimensions and the characteristics of the sclerotic male apparatus. The new species appears more similar to P. fibulata collected in the Mediterranean Sea.