Pseudoplatycoma, Chen, Cheng-Ann, 2015

Chen, Cheng-Ann, 2015, A new marine nematode genus Pseudoplatycoma with a new species from the Sulu Sea and revision of the subfamily Platycominae (Enoplida: Leptosomatidae), Zootaxa 3905 (2), pp. 233-244 : 234

Genus Pseudoplatycoma n. gen.

Description. Male Body long, diameter uniform except near anterior and posterior ends. Cuticle smooth. Ocelluslike paired pigment spots throughout the body from posterior to the nerve ring to the anterior of the spicule. Labial papillae not clearly observed. Eight cephalic setae. Three stout cervical setae near the posterior of the amphid. Four somatic setae on the left side but absent on the right side. One seta on esophageal region (as well as three stout cervical setae). Virtually no buccal cavity; mouth opening merging into oesophagus. Oesophagus cylindrical; length approximately one sixth of the total body length. Amphids pocket-like. Tail conical.

Spicules paired, slightly curved ventrally. Proximal end of spicule bluntly rounded. Distal end of spicule forming a screw-like pattern. Gubernaculum with paired dorsal apophyses, caudally directed. Paired subventral setae present at the cloaca. A small pre-cloacal supplement present. One caudal seta present at the tail region. Six pairs of heavily cuticularized paired tubular supplements.

Female. Similar to male except for reproductive structures and larger body which is also longer relative to diameter. Head diameter and amphid smaller than male. First pigment spot further from anterior and nerve ring compared to the male. Vulva near mid body length. Reproductive system didelphic amphidelphic. Tail relatively longer than in male.

Diagnosis. The characteristics most distinguishing the new genus from the other genera in subfamily Platycominae are the presence of paired heavily cuticulatized tubular precloacal supplements, spicules bluntly rounded at the proximal end, and ocellus-like paired pigment spots throughout the body from posterior to the nerve ring to the anterior of the spicule. No other genus in the subfamily has these characteristics, together with cupshaped or pocket-like amphids with posterior cervical setae. The genus Platycomopsis Ditlevsen 1926 has cupshaped or pocket-like amphids with posterior cervical setae, but has spicules funnel-shaped at the proximal end and ocelli-like paired pigment spots are absent throughout the body. In the presence of a group of cervical setae situated close together and posterior to the amphids, but not immediately so, Pseudoplatycoma n. gen. closely resembles the genus Platycoma (as defined in Table 2). However, Platycoma has oval or slit-like amphids with posterior cervical setae. Proximally bluntly rounded spicules, together with gubernaculum apophyses which are caudally directed are only reported in the genus Proplatycoma , as is a pre-cloacal supplement followed by six subventral papillae. Proplatycoma has a conical pointed, arrowhead-shaped or branched amphid in males, unlike Pseudoplatycoma n. gen..

Etymology. The genus name refers to the dissimilarity with the genus Platycoma .