Two New Species of Free-Living Marine Nematode of the Genus Anticyathus Cobb, 1920 (Linhomoeidae) from Mangroves Sediment of Shenzhen and Shantou, China

Two new species belonging to the genus Anticyathus were discovered during an ecological investigation of mangrove sediment in China. Anticyathus shenzhensis sp. nov. and Anticyathus communis sp. nov. are both characterized by: annulated cuticles; ten cephalic setae in a circle; buccal cavity lined with six longitudinal reinforcements; amphids in broken circles or cryptic spirals, located at the very anterior of the head; pharynx with anterior cuticularized, gradually enlarging in posterior portion but without bulb; conical tail; arcuate spicules, the distal ends pointed, gradually broadening towards the proximal; gubernaculum has a dorsal-caudal apophysis; female with two opposed, outstretched ovaries. Anticyathus shenzhensis sp. nov. can be distinguished by ten cephalic setae of length about 2-4 mu m; amphids diameter about 20-29% of corresponding body diameter; pharynx occupy 0.07-0.10 times of body length; cardia length about 25 mu m; tail length 2.5-3.4 times of anal body diameter (abd) in males and 3.4-4.7 abd in females; spicules length 51-59 mu m as arc and 0.71-1.04 abd; apophysis length 18-19 mu m; female vulva at 52-56% of body length. Anticyathus communis sp. nov. is identified by ten cephalic setae length about 3-5 mu m; amphids diameter about 20-32% of corresponding body diameter; cardia 17-27 mu m long; tail length 3.6-4.5 abd in male, 5.3-5.5 abd in female; spicules proximal with distinctly cephalated, 0.74-0.96 abd; gubernaculum shape of "L", consisting of sleeves around spicule and dorsal-caudal apophysis; five to seven pre-anal and seven to ten post-anal almost invisible papilla or papillae-like setae occur on each ventrally submedian line on the posterior body part of male; the tip of male tail with three slight elevation; female vulva at 52% of body length. A dichotomous key for the genus Anticyathus is given and 39 sequences of 18S rRNA gene from ten individuals of Anticyathus shenzhensis sp. nov. are provided in Genbank database.