Two Species of Free-Living Nematodes of the Genus <i>Daptonema</i> Cobb, 1920 (Nematoda, Monhysterida) New for Science from Artificial Reservoirs of Vietnam
An illustrated description of two new species of free-living nematodes of the genus Daptonema, D. lutosum sp. n. and D. stagnalis sp. n., found in artificial reservoirs for shrimp aquaculture in Vietnam is given. D. lutosum sp. n. is close to D. borealis Gagarin, 2020 and D. dihystera Gagarin, Nguyen Vu Thanh, 2005 in the structure of the spicular apparatus and body size. It differs from D. borealis Gagarin, 2020 by longer outer labial setae, posterior location of amphidial fovea from the anterior body end, shorter spicules and presence of posterior uterus in females; it differs from D. dihystera Gagarin, Nguyen Vu Thanh, 2005 by a shorter pharynx, longer outer labial setae, posterior location of amphidial fovea from the anterior body end and longer terminal setae at the tail tip. D. stagnalis sp. n. is the most similar to D. dihystera and D. lutosum sp. n. in the structure of the spicular apparatus and body size. It differs from both species in thicker body, more slender tail and absence of posterior uterus in females. The table of the main morphometric characters in males of the valid species from the ”swalbardensis” species group of Daptonema is presented.