Fotolaimus Belogurova & Belogurov, 1974

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

Genus Fotolaimus Belogurova & Belogurov, 1974

Type species.

Fotolaimus marinus Belogurova & Belogurov, 1974.

Diagnosis

(modified from Belogurova and Belogurov 1974). Oncholaiminae . Left ventrosublateral tooth larger than the two other teeth. Spicules shorter than 2.0 cloacal body diameters. Gubernaculum present. Demanian system present, posterior end of main duct forming two symmetrical sacs each with five or more terminal ducts.

Remarks.

The genus Fotolaimus can be distinguished from Metaparoncholaimus and Wiesoncholaimus by the left ventrosublateral tooth being larger than the right ventrosublateral tooth (left and right ventrosublateral teeth are equal in size in Metaparoncholaimus and Wiesoncholaimus ). It also differs from Prooncholaimus by the absence of the large bubble-like cells in pseudocoelom (presence in Prooncholaimus ). Fotolaimus , Oncholaimus , and Metoncholaimus are similar to each other and are distinguished by the morphological characters of the terminal ducts of the Demanian system. Belogurova and Belogurov (1974) characterized the Demanian system of Fotolaimus as follows: the posterior end of the main duct forms two symmetrical sacs, each of which is pierced by five terminal ducts ending in terminal pores. On the other hand, the main ducts of Oncholaimus and Metoncholaimus do not form a sac at the posterior end, but branch separately into two or more terminal ducts ( Belogurov and Belogurova 1988). Belogurov and Belogurova (1977) distinguished Metoncholaimus from Oncholaimus in that the terminal ducts are covered with moniliform glands. However, some Metoncholaimus species do not mention the shape of the terminal duct in their description (e.g., Mawson 1958; Salma et al. 2017). For convenience, a species may be considered belonging to Oncholaimus if it has short (equal to cloacal body diameter) spicules and without gubernaculum, and belonging to Metoncholaimus if it has longer spicules (with or without gubernaculum) or short spicules with gubernaculum (cf. Platt and Warwick 1983). The distinction between Oncholaimus and Metoncholaimus will need to be reexamined in the future.