This paper reports on the genus Cobbionema Filipjev, 1922 in Sweden with the description of four species and a revision of the genus. Cobbionema acrocerca Filipjev, 1922 is relatively small in size, with a tail that has a conical proximal and a digitate distal section. Cobbionema cylindrolaimoides Schuurmans Stekhoven, 1950 is similar to C. acrocerca in most characters except having a larger body size and heavily cuticularized mandibles. Cobbionema brevispicula sp. nov. is characterised by short spicules and a conoid tail. Cobbionema acuminata sp. nov. is characterised by a long two-part spicule, a conical tail and three (one mid dorsal and two ventrosublateral) sharply pointed tines in the anterior chamber of the stoma that are located more anterior than in all the other species. We also present a molecular phylogeny of the family based on the nearly full-length 18S and the D2-D3 expansion segment of the 28S rRNA genes. Maximum Likelihood and Bayesian trees inferred from both genes strongly support a clade that included Cobbionema, Demonema Cobb, 1894 and Halichoanolaimus de Man, 1888 and another clade with Gammanema Cobb, 1920 and Latronema Wieser, 1954 nested together. None of the trees supported the monophyly of the subfamilies Choniolaiminae and Selachinematinae.
Almost 370 samples were collected from three typesof habitats, viz. fellfield soils, mosses and ornithogenicsoils, on 14 mountain outcrops penetrating the ice sheet(nunataks) and one oasis in Dronning Maud Land, EastAntarctica. The samples were analyzed for metazoan microfauna(nematodes, rotifers and tardigrades). Studiesreveal that the populations of microfauna are patchilydistributed. Fauna composition of the microscopic animalswas found to vary greatly also among samples fromsimilar types of habitats. The presence of seemingly similarhabitable sites lacking microfauna and sites withdifferent combinations of animal taxa indicates that randomcolonization processes as well as local environmentaland historical factors might influence fauna compositionin specific habitable patches.
A new species of Paracrobeles, P. kelsodunensis sp. nov. is described from the Kelso Dunes area, Mojave National Preserve, southern California. Paracrobeles kelsodunensis sp. nov. is particularly characterised by a body length of 469–626 μm in females and 463–569 μm in males; lateral field with four incisures, extending almost to tail terminus; three pairs of asymmetrical lips, separated by U-shaped primary axils with two long guarding processes, each lip usually with four tines along its margin; three long labial probolae, deeply bifurcated, with slender prongs without tines; metastegostom with a strong anteriorly directed dorsal tooth; pharyngeal corpus anteriorly spindle-shaped, posteriorly elongate bulbous with dilated lumen; spermatheca 24–87 μm long; postvulval uterine sac 60–133 μm long; vulva in a sunken area; spicules 33–38 μm long; and male tail with a 5–8 μm long mucro. The generic diagnosis is emended on the basis of recently described species and a key to the species of Paracrobeles is provided.
Populations of Stegelleta are described from California, New Zealand and Senegal. An amphimictic population from California is identified as belonging to S. incisa and compared with type specimens from Utah and an amphimictic population from Italy. One population from New Zealand is close to S. incisa but considered to represent a new species, Stegelleta laterocornuta sp. nov. It is particularly characterised by a 379–512 μm long body in females and 365–476 μm in males; cuticle divided into 16 rows of blocks at midbody (excluding lateral field); lateral field with four incisures; three pairs of asymmetrical lips, U-shaped primary axils without guarding processes, each lip asymmetrically rectangular with a smooth margin, only lateral lips have slender acute tines; three labial probolae, bifurcated at half of their length; vulva without flap; spermatheca 17–31 μm long; postuterine sac 7–24 μm long; spicules 21.5–23.5 μm long. Other specimens from New Zealand are identified as belonging to S. tuarua. A parthenogenetic population from Senegal is identified as belonging to S. ophioglossa and compared with type specimens from Mongolia and records of several other populations of S. ophioglossa. The generic diagnosis is emended and a key to the species of Stegelleta is provided.
Leptolaimus timmi Vitiello, 1971 is redescribed from bottom sediments collected in the Skagerrak off the west coast of Sweden. New morphological data necessitate the transfer of this species to the genus Rhadinema Cobb, 1920. The main diagnostic characters of Rhadinema timmi (Vitiello, 1971) comb. n. include: 1.3–1.8 mm long body; rounded labial region weakly offset from body contour; cephalic setae 2–4 μm long; amphid located 12–19 μm from anterior end; first body pore located 22–30 μm from anterior end; lateral field absent; stoma tubular: cheilostom with six weakly cuticularised longitudinal rugae, gymnostom with sclerotized bar-shaped rhabdia, stegostom long, tubular; female without supple- ments, vagina without pars refringens, vulva midventral; male with 10–11 tubular and without alveolar supplements; spic- ules arcuate and 21–30 μm long.
A new genus Neocamacolaimus gen. n., with one new species N. parasiticus gen. n., sp. n. is described from the benthic polychaete Sphaerosyllis cf. hystrix collected in the Skagerrak off the west coast of Sweden. Neocamacolaimus gen. n. is placed in the family Camacolaimidae and is particularly characterised by having annulated cuticle with lateral alae; seti- form cephalic sensilla located at level with amphids; amphidial fovea ventrally spiral; buccal cavity without armament; pharynx muscular; nerve ring located at base of pharynx; male reproductive system diorchic with outstretched testes; spic- ules weakly arcuate with straight manubrium; gubernaculum absent; alveolar supplements located in the pharyngeal re- gion; tubular supplements absent; tail conoid; caudal glands and spinneret present. Juveniles of this genus are particularly characterised by their parasitic lifestyle and the following unique morphological features: lips form a dorso-ventrally elon- gated perioral disc with internal sclerotizations: one midventral and two dorsosublateral (right and left); cephalic sensilla setiform, subventral sensilla are noticeably longer than the subdorsal ones; intestine extends posterior to rectum and anal opening, forming a post-anal pouch.
The new genus and species Yeatesinia barbata gen. n., sp. n. is described from a sand dune habitat in New Zealand. The new genus is characterised by a body length of 299-357 μm in females and 304-361 μm in males, lip region rounded dorso-ventrally, broad laterally, dorsally inclined, lateral sides of lip region with two large, horn-like, projections, each bearing one seta at its base, each amphid surrounded by three setiform sensilla, oral opening a broad transverse slit located on the dorsal body surface, and different structure of cuticle in the dorsal and ventral body sectors. This combination of unique morphological characters clearly separates the new genus from all other members of the Plectidae. The phylogenetic affinities of Yeatesinia gen. n. and its relationships to other genera of the family Plectidae are discussed.