Sphaerolaimidae Filipjev, 1918

Tchesunov, Alexei V., Eskandari, Ali, Hosseinvand, Manouchehr & Hajializadeh, Parima, 2024, Free-living marine nematodes of the family Sphaerolaimidae (Chromadoria, Monhysterida) from the mangroves of the Qeshm Island, Persian Gulf, Zootaxa 5468 (3), pp. 523-540 : 524-525

Family Sphaerolaimidae Filipjev, 1918

Emended diagnosis. Cuticle optically smooth or finely striated, sometimes with longitudinal alae. Anterior sensilla pattern with six inner labial papillae and 10 short setae (six outer labial setae and four cephalic setae joined in a common crown). At stoma level, one or two circles of eight groups of subcephalic setae significantly longer than both outer labial and cephalic setae. Buccal cavity is mostly large barrel-shaped and the cheilostoma constitutes its major part. The cheilostoma consists of three compartments, anterior conical labial region, striated truncate conical region with fine longitudinal ribbing, and broad or narrow barrel-shaped shagreen band (shagreen band or chagrinierter Teil of German authors is an internal cuticular layer of the broadened posterior part of cheilostoma in Sphaerolaimus and some other sphaerolaimids; complicated sclerotized texture of this layer resembles shagreen skin). Gymnostoma as a narrow band. Stegostoma cup-shaped or elongate conical, with heavily cuticularized walls. Pharynx cylindroid, evenly muscular throughout its length, with very thick internal cuticular lining. Amphideal fovea circular, situated at the level of the gymnostoma or further posteriorly. Ventral excretory/secretory gland present, ventral pore usually just posterior to the nerve ring. Only one anterior outstretched ovary. Diorchic (rarely monorchic), anterior testis outstretched and posterior testis reflected, situated at opposite sides of the intestine. Tail usually with a cylindrical posterior part with slight terminal swelling, more rarely rounded conical. Two or three terminal setae on the tail tip. Marine.

Type genus: Sphaerolaimus Bastian, 1865 .

Remarks. Lorenzen (1978, 1981, 1994) insists on a character that four cephalic setae of the third sensilla circle are always longer than the six outer labial setae, whereby both circles are joined at the same level. He appraises this as a holapomorphy of the Sphaerolaimidae . We could not confirm this state since both cephalic and outer labial setae coupled in pairs are so short, that a difference in length between them is hardly conceivable, especially as they are situated athwart to the observer.