Oigolaimella kruegeri n. sp. and Oigolaimella ninae n. sp. are described. Oigolaimella kruegeri n. sp. males can be recognised by the lack of the gubernacular keel characteristic of other Oigolaimella species and by the modified distribution pattern of the genital sensillae. Oigolaimella ninae n. sp. can be recognised and distinguished from the other members of the genus by the refractive cuticularised ring formed by the anterior edge of the cheilostomatal collar. Oigolaimella longicauda (Claus, 1862) n. comb. is accepted as a valid species, regarded as a senior synonym of O. agilis (Skwarra, 1921) and redescribed. Oigolaimella diplogaster (von Linstow, 1890) n. comb. is proposed. The phylogenetic relationship of Oigolaimella is discussed and an ecological characterisation of the taxon given on the basis of observations on feeding behaviour and locomotion in the habitat.
A new hermaphroditic species belonging to the diplogastrid taxon Koerneria is described. Although Koerneria sudhausi n. sp. displays all known apomorphies of Koerneria, it shares apomorphic characters with Mononchoides colobocercus (originally described as Diplenteron colobocercus). I assume that the apomorphic features of Koerneria exist in M. colobocercus too and were overlooked in the original description. Consequently M. colobocercus is transferred from Mononchoides to Koerneria, becoming Koerneria colobocerca n. comb. Koerneria sudhausi n. sp. and its sister species, K. colobocerca, together form the Diplenteron species group within Koerneria. Characteristic features of K. sudhausi n. sp. are the species group-specific prerectum in combination with a short but pointed tail in both sexes. In K. sudhausi n. sp. a stoma dimorphism between stenostomatous and eurystomatous morphs occurs. Eurystomatous K. sudhausi n. sp. hermaphrodites lack two denticles in the armature of the left subventral stegostomatal sector. All adults possess pore-like amphids. Although K. sudhausi n. sp. is hermaphroditic, a considerable frequency of males (up to 16.6%) occurs. In cultures of K. sudhausi n. sp. males are functional. In K. sudhausi n. sp. males, the phasmid is situated between caudal papillae v6 and v7. The formation of a secondary egg shell by a uterine shell gland is described. Koerneria sudhausi n. sp. possesses an exceptionally high number of intestine cells, an inexplicable dimorphism in egg length, and a dauer juvenile that lacks the oily substance usually found in diplogastrid dauers.
A new species of the diplogastrid genus Oigolaimella is described in colonies of termites belonging to the genus Reticulitermes from Corsica (France) and USA. Oigolaimella attenuata n. sp. males can be recognised by the conspicuous length of the ventral unkeeled part of the otherwise keeled gubernaculum and, in contrast to the other members of the genus, the fact that the lateral field of both adult stages is marked by a single line. A diagnostic key for the five species of Oigolaimella is presented. Life cycle and development, including spermiogenesis, sperm transfer, sperm competition and fertilisation are described in detail. Some interesting aberrations of the reproductive system are documented. The new species uses the preoral cavities of the termites for internal phoresis and is associated with non-pathogenic gut-inhabiting flagellates of the taxon Kinetoplastida. The heads of 76 of 117 examined termites were infested with dauer juveniles of O. attenuata n. sp. with an average of 6.4 nematodes per termite. Six additional nematode species were isolated from the bodies of the termites, particularly a species of Pristionchus and, for the first time, Halicephalobus sp., Mesorhabditis spiculigera and Rhabditella axei. Rhabpanus ossiculum was isolated from termite-inhabited wood from Corsica, the first such detection in Europe. In the course of our discussion of the literature on termite-associated nematodes, we propose the new combination Pristionchus formosianus (Poinar, Meikle & Mercadier, 2006) n. comb. (=Chroniodiplogaster formosiana).
A new species of the nematode taxon Diplogastridae is described on morphology and additional molecular data. The new species cannot be grouped in any of the currently accepted diplogastrid genera. Therefore, we introduce the new genus Cutidiplogaster n. gen. along with the description of our new species Cutidiplogaster manati n. gen., n. sp. Cutidiplogaster manati n. gen., n. sp. was isolated from skin lesions of manatees, Trichechus manatus manatus, kept in Okinawa Churaumi Aquarium, Japan. The specimens were found anchored with their extraordinarily long tails to the small, thick epidermal bumps within thread algae that form part of the epizoic community on the manatee skin. Cutidiplogaster manati n. gen., n. sp. is characterised by the tube-shaped and finely annulated postdental part of the stegostom that makes it distinct from all other Diplogastridae so far known, and the coiled long tail that makes it unique in comparison with all known diplogastrids. On the basis of detail in stoma morphology in C. manati n. gen., n. sp., we discuss implications in homologising diplogastrid mouthparts and their evolution.