Metoncholaimus amplus Hopper, 1967

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 : 550-551

Metoncholaimus amplus Hopper, 1967

( Figs 1 A–D & 2)

Material examined. One female and one male were examined from Diapterus rhombeus .

Measurements. See Table 1 .

Description. Adults: Body 2.33–3.43 mm long. Cuticle smooth without ornamentations. Lip region with no visible labial papillae or setae. Amphids pocket-like with oval aperture, located at the base of the lip region. Stoma almost as long as wide, having three teeth, the left ventrosublateral larger, while the dorsal and the right ventrosublateral have similar size. Pharynx cylindrical and not expanded at posterior region. Nerve ring surrounding the pharynx slightly posterior of its middle length. Excretory pore not observed. Cardia undifferentiated. Intestine not discernible, in bad condition.

Female: Body with sigmoid habitus. Reproductive system monodelphic-prodelphic; ovary and oviduct in bad condition, uterus tubular with eggs in different stages of development, 81 x 108 Μm. Demanian system located between vulva and anus, in bad condition. Rectum not seen. Tail conoid elongate, distally slightly clavate, ending in a spinneret.

Male: General morphology similar to female, also with sigmoid habitus. Spicules very long and slender, with well-developed manubrium. Gubernaculum present, short and ventrad curved, bearing a small ventral apophysis. Genital setae nine, disposed ventrally anterior and posterior to the cloacal aperture. Tail conoid elongate, straight, posteriorly clavate.

Distribution. M. amplus was reported from Florida ( USA) by Hopper (1976) in littoral and sublittoral soft sediments. From Brazil, it was reported as a pseudoparasite in fishes ( Moravec et al. 1990) but not as a free-living species (see Venekey et al. 2010).

Remarks. The material studied is similar to published descriptions, but some differences were noted. From the type material examined by Hopper (1967) it differs in: shorter body length (2.33 mm in the present material vs 3.54–5.53 mm) and width (45–76 µm vs 68–90 µm) although this appears contracted in some parts, lip region narrower (25–27 µm vs 30–35 µm), stoma slightly shorter (20–27 µm vs 34–45 µm), female tail shorter (94 µm vs 138–215 µm), male tail (92 µm vs 96–175 µm) and spicules slightly longer (172 µm vs 103–142 µm). The material from Brazil studied by Moravec et al. (1990) had a longer body length in females (2.33 mm vs 3.66–4.11 mm), shorter male stoma (25 µm vs 33–39 µm), longer male pharynx (670 µm vs 340–394 µm) and shorter spicules (172 µm vs 198–306 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.