Oncholaiminae Filipjev, 1916

Shimada, Daisuke, Kakui, Keiichi & Fujita, Yoshihisa, 2023, A new species of free-living marine nematode, Fotolaimus cavus sp. nov. (Nematoda, Oncholaimida, Oncholaimidae), isolated from a submarine anchialine cave in the Ryukyu Islands, southwestern Japan, Zoosystematics and Evolution 99 (2), pp. 519-533 : 519

Subfamily Oncholaiminae Filipjev, 1916

Type genus.

Oncholaimus Dujardin, 1945.

Diagnosis

(modified from Belogurova and Belogurov 1974; Smol et al. 2014). Oncholaimidae . Cuticle smooth. Buccal cavity barrel-shaped, with three teeth. Left ventrosublateral tooth larger than other teeth (usual) or left and right ventrosublateral teeth of same size. Spicules short or long, gubernaculum present or absent. Copulatory bursa absent. Female reproductive system monodelphic-prodelphic with an antidromously reflexed ovary. Demanian system present or absent.

Remarks.

Cobb (1930) established the new genus Oncholaimium Cobb, 1930, which differs from Oncholaimus mainly by the presence of a distinct precloacal appendicule (papilla) in males. Subsequently, Kreis (1932) established Pseudoncholaimus Kreis, 1932 based on the lack of Demanian system. Kreis (1934) also distinguished Oncholaimium from Oncholaimus based on the Demanian system, which is without terminal pore in Oncholaimium and with terminal pores in Oncholaimus . However, Rachor (1969) synonymized Oncholaimium and Pseudoncholaimus to Oncholaimus , because the presence of a Demanian system is unknown for many species of Oncholaimus . Belogurov and Belogurova (1988), who proposed the currently accepted taxonomic system of Oncholaimidae , treated Oncholaimium and Pseudoncholaimus as valid genera. Pseudoncholaimus is still considered valid by several researchers (e.g., Smol et al. 2014; Tsalolikhin 2015; Milovankina and Fadeeva 2019). However, because it is unclear for numerous species whether they rather belong to Oncholaimus , Oncholaimium , or Pseudoncholaimus , we included the latter two in Oncholaimus sensu lato as described by Rachor (1969). Thus, the subfamily Oncholaiminae comprises six genera, i.e., Oncholaimus , Metoncholaimus , Prooncholaimus Micoletzky, 1924, Metaparoncholaimus De Coninck & Schuurmans Stekhoven, 1933, Wiesoncholaimus Inglis, 1966, and Fotolaimus . Members of the Oncholaiminae can be distinguished from these of the other six subfamilies as follows. They are distinct from Krampiinae De Coninck, 1965, Adoncholaiminae Gerlach & Riemann, 1974, and Pontonematinae Gerlach & Riemann, 1974 as they have only one ovary (whereas the three other genera have two); from Pelagonematinae De Coninck, 1965 and Octonchinae De Coninck, 1965 as they have three distinct teeth (whereas Pelagonematinae member have minute or no tooth and Octonchinae have eight or more); and from Oncholaimellinae De Coninck, 1965 because their left ventrosublateral tooth is larger than the other two teeth (right ventrosublateral tooth is larger in Oncholaimellinae ). Recent revisional works were provided by Mawson (1958) for Metaparoncholaimus , Yoshimura (1982) for Metoncholaimus , and Chen et al. (2015) for Prooncholaimus .