Oncholaimellus labiatus ( Kreis, 1932 ) Gerlach & Riemann, 1974

Abolafia, Joaquín, Ruiz-Cuenca, Alba N., Fernandes, Berenice M. M., Cohen, Simone C. & Cárdenas, Melissa Q., 2015, Description of free-living marine nematodes found in the intestine of fishes from the Brazilian coast, Zootaxa 3948 (3), pp. 549-572 : 557

Oncholaimellus labiatus ( Kreis, 1932) Gerlach & Riemann, 1974

( Figs 1 I–K & 4)

Material examined. Three females and two males were examined from Diapterus rhombeus .

Measurements. See Table 1 .

Description. Adults: Body 1.27–1.80 mm long. Cuticle smooth, lacking striations and ornamentations. Lip region with both labial papillae and cephalic setae not visible. Amphids not visible. Stoma three times longer than wide, bearing three teeth, the right ventrosublateral one larger and highly refringent, and the dorsal and the left ventrosublateral ones having a smaller similar size; stomatal cavity divided by a sclerotized transversal band. Pharynx almost cylindrical. Nerve ring surrounding pharynx slightly posterior to its mid-length. Excretory pore not observed. Cardia undifferentiated. Intestine in bad condition.

Female: Body with sigmoid habitus. Reproductive system didelphic-amphidelphic; ovaries and oviducts in bad condition, uteri tubular with numerous eggs 37 x 79 Μm. Demanian system simple, forming an expansion of the ovary in its reflexed part and connecting to the intestine. Rectum not seen. Tail conoid elongate, ending in a small spinneret.

Male: General morphology similar to female, also with sigmoid habitus. Spicules long and slender, about 2.5 times anal body diameter, manubrium well developed. Gubernaculum present but very reduced. Genital setae and bursa absent. Tail conoid elongate, slightly ventrad curved and ending in a small spinneret.

Distribution Oncholaimellus labiatus was reported by Kreis (1932, 1934) from the Banda and Java seas, the Sunda Strait and the Kai Islands ( Indonesia) and by Gerlach (1964) from the Red Sea. This is its first report from Brazil (see Venekey et al. 2010).

Remarks. The material examined from Brazil is similar to that examined by Kreis (1932, 1934), but some differences occur: body slightly longer in females (1.58–1.80 vs 1.53–1.59 mm long), shorter tail (64–139 vs 97– 234 µm, c'= 5.8–10.7 vs 5.6 in females and 84–91 vs 131–140 µm, c'= 4.9–7.6 vs 5.7 in males). It differs from the material examined by Gerlach (1964) in having smaller males (1.27–1.45 vs 1.63 mm long), more posterior vulva position (V= 69–80 vs 53), less slender tails (vs c'= 3.7 in female and c'= 3.6 in male) and slightly shorter spicules (22–32 vs 36 µm).

Figures

FIGURE 1. Metoncholaimus amplus Hopper, 1967. A: Stoma. B: Neck. C: Female posterior end. D: Male posterior end. Prooncholaimus ornatus (Kreis, 1932) Kreis, 1934. E: Stoma. F: Neck. G: Female posterior end. H: Male posterior end. Oncholaimellus labiatus (Kreis, 1932) Gerlach & Riemann, 1974. I: Stoma. J: Female posterior end. K: Male posterior end.