Nordadriatische Gastrotrichen

Abstract

Twentytwo new and 8 known species of gastrotrichs are described from eulittoral and sublittoral sandy bottoms of the northern Adriatic Sea. The MgCl2 method was used for extraction from the substrate. Only living material was studied employing phase contrast microscopy. Seven of the new species belong to the order Macrodasyoidea, 15 are members of the order Chaetonotoidea. In Macrodasys caudatus, 4 different types of bursae copulatrices were found to be usually correlated with a specific number of mature and immature eggs. In 2 new species of Tetranchyroderma, the four-pronged hooks are restricted to narrow bands; another species of that genus has four-pronged hooks only in the pharyngeal region being reduced to small lateral patches. Four new species of Chaetonotus belong to the schultzei group; the diagnostic feature of this group is the tri-cornered spine whose distal edge is more oblique and extends always in only one fine tip. Halichaetonotus is given the rank of a genus distinct from Chaetonotus; the diagnostic feature of Halichaetonotus species is the dorsal occurrence of both keeled scales and of spines, as well as the ventrolateral spined scales or foliaceous scales. Four new species of Heterolepidoderma lead to the discussion of the characters of the genus. Species belong to Heterolepidoderma if they are covered by keeled scales only or by keels lacking a distinct base scale. The number of longitudinal rows composed by these cuticular elements is, at the present, of no value to the diagnosis of the genus. © 1972 Biologischen Anstalt Helgoland.