Cyatholaimus minor, Gagarin, Vladimir G., 2012

Gagarin, Vladimir G., 2012, Paracanthonchus multisupplementatus sp. n. and Cyatholaimus minor sp. n. (Nematoda) from the coast of Vietnam, Zootaxa 3392, pp. 60-68 : 64-66

Cyatholaimus minor sp. n.

(Figs 2.3; Table 2)

Type material. Holotype male, slide reference number 100/47, deposited in the collection of the Institute of Ecology and Evolution, Center for Parasitology, Russian Academy of Sciences, Moscow, Russia.

Paratypes. One male and three females deposited in the collection of the Institute of Ecology and Biological Resources Vietnamese Academy of Sciences and Technology, Hanoi, Vietnam.

Measurements. Table 2.

Type locality. South China Sea, Tra Co, Quang Ninh province, Vietnam, littoral zone. Latitude: 21º26'811", Longitude: 107º59'632". Depth 2.5 m, sand, salinity 29.1‰. Collected in March 2010.

Etymology. The specific epithet means “small”, "having small body.”

Description. Male. Body short and comparatively thin. Cuticle transversally annulated and punctated. The dots (punctations) about the same size along the body and closely arranged in transverse rows. No clear lateral differentiation in size and position of the dots. Cuticular pores distinct, comparatively large and located on cuticle from the anterior pharynx portion to the middle of the tail. There are small somatic setae sparsely distributed along the body. Anterior end of body truncate. Mouth opening surrounded by conical lips with barely visible inner labial sensillae. Outer labial and cephalic sensilla constitute a jointed circle of 6+4 short setae. Four cephalic setae slightly smaller than six outer labial setae. Outer labial setae 25–29% of labial region width. Amphidial fovea large, round, multispirally coiled with about seven and a half turns and located at the level of stoma. Cheilostom narrow, its walls reinforced by sclerotized rugae apparently twelve in number. Esophastom cup-shaped and armed with pointed, sclerotized tooth on the dorsal wall of stoma and two small denticles on both subventral walls. Eyespots poorly visible, situated at a distance 23–24 µm from anterior body end or 2.0–2.1 labial region widths. Pharynx evenly muscular throughout its length, widening posteriorly but not forming a true bulb. Cardia muscular but poorly visible.

Diorchic; anterior testis outstretched, posterior smaller testis reflexed. Anterior testis situated to the right of the intestine, posterior testis to the left of the intestine. Spicules thin, curved, with small, oval capitulum. Gubernaculum slightly shorter than spicules, paired with massive, spherical widening at distal end, bearing 4–6 thorns. Supplements absent. Tail elongate-conical, gradually narrowing, curved ventrally with delicate terminal spinneret in the shape of conical tube. Three caudal glands poorly visible. There are 10–13 lateroventral and laterodorsal setae on the tail.

Female. General morphology is similar to that of males in structure of cuticle and anterior body end. Cuticle transversely annulated and punctated. Cuticular pores distinct, comparatively large. Anterior end of body truncate. Inner labial sensilla in the shape of conical papillae. Outer labial and cephalic sensilla constitute a jointed circle of 6+4 short setae. Four cephalic setae slightly smaller than six outer labial setae. Amphidial fovea large, round, multispirally coiled with about three and a half turns and deposed at the level of stoma. Eyespots poorly visible, situated 24–26 µm from anterior body end. Cheilostom narrow, its walls reinforced by sclerotized rugae. Esophastom cup-shaped, with large pointed tooth on its dorsal wall and two small denticles on the both subventral walls. Pharynx evenly muscular throughout its length, widening posteriorly but not forming a true bulb. Rectum 0.9–1.1 times as long as anal body diameter.

Didelphic, ovaries antidromously reflexed. Anterior ovary situated to the right of the intestine, posterior ovary to the left of the intestine. Terminal zone of oogonia arranged in one or two rows; growth zone with a single row of gradually enlarging oocytes. Vagina with slightly muscular walls, occupying 25–30% of corresponding body width. Uterus spacious, filled with small rounded spermatozoa and containing one egg measuring 43– 46 x 22–24 µm. Vulva a transverse slit, situated slightly posterior to mid-body. Vulval lips unsclerotized, protruding outside the body contour. Tail slender, elongate-conical, gradually narrowing, curved ventrally. Caudal glands and spinneret present. A few small caudal setae present.

Diagnosis. Body 532–543 µm long in males, 645–710 µm long in females. Cuticle transversely annulated and punctated. Cuticular pores distinct, comparatively large. Inner labial sensilla in the shape of conical papillae. Outer labial and cephalic sensilla constitute a jointed circle of 6+4 short setae. Amphidial fovea large, round, multispirally coiled with about seven and a half turns in males and with about three and a half turn in females. Eyespots poorly visible, situated 1.7–2.1 labial region widths from anterior body end. Stoma with big pointed tooth on the its dorsal wall and two small denticles on the both subventral walls. Pharynx evenly muscular throughout its length, widening posteriorly, but not forming a true bulb. Didelphic, ovaries antidromously reflexed. Vulva a transverse slit, situated slightly posterior to mid-body. Diorchic; anterior testis outstretched, posterior smaller testis reflexed. Spicules thin, curved, with small oval capitulum. Gubernaculum paired, with massive, spherical widening at distal end and bearing pointed appendages. Gubernaculum slightly shorter than spicules. Supplementary organs absent. Tail elongate-conical, gradually narrowing, curved ventrally. Caudal glands and spinneret present.

Differential diagnosis. Cyatholaimus minor sp. n. is similar to C. ocellatus Bastian, 1865 in structure of spicular apparatus, but differs from it in the shorter body (L = 532–710 µm versus L = 1.10–1.79 mm in C. ocellatus ), more slender tail (c’ = 3.5–4.3 versus c’ = 2.5–2.8 in C. ocellatus ), larger dorsal tooth in stoma and shorter spicules and gubernaculum (spicules 21–22 µm long, gubernaculum 19–20 µm long versus spicules 60 µm long, gubernaculum 52 µm long in C. ocellatus ( Bastian, 1865; Wieser, 1956).