Mudwigglus nellyae (Vincx and Gourbault, 1992) Vincx and Gourbault, 1992

Leduc, Daniel, 2013, Mudwigglus gen. n. (Nematoda: Diplopeltidae) from the continental slope of New Zealand, with description of three new species and notes on their distribution, Zootaxa 3682 (2), pp. 351-370 : 366-369

Mudwigglus nellyae (Vincx and Gourbault, 1992) comb. n.

( Fig 10 , Table 1)

Specimens. Two males, collected on 5 June 2007 (NIWA cruise TAN0707, station 113), western Challenger Plateau (40.874° S, 170.851° E), water depth: 544 m, silt/clay content: 67.6%, CaCO3 content: 56%, sediment chlorophyll a concentration: 21 ng /gDW sediment (NIC 865984). One male, collected on 4 June 2007 (NIWA cruise TAN0707, station 99), western Challenger Plateau (40.132° S, 170.212° E), water depth: 803 m, silt/clay content: 83.3%, CaCO3 content: 69%, sediment chlorophyll a concentration: 15 ng /gDW sediment (NIC 865985).

Description. Males. Cylindrical body, colourless, tapering slightly towards the anterior extremity. Cuticle 1 Μm thick, with annuli beginning at level of cephalic setae to near tail tip, situated ca. 2 Μm apart, no lateral differentiation. Somatic setae short and sparse. Hypodermal glands not observed. Two pairs of subventral setae, one pair of subdorsal setae, and three short terminal setae on tail. Labial region rounded, not set off. Inner labial sensillae not observed. Six minute outer labial sensillae and four cephalic setae, 1 Μm long. Subcephalic setae absent. Fovea amphidialis an elongated loop, with cuticularised outline, ca. 2 times longer than wide. Buccal cavity cup- or funnel-shaped, separated from anterior extremity by narrow mouth opening surrounded by bulge of inner portion of lip region. Walls of buccal cavity not cuticularised. Teeth not observed. Pharynx short, cylindrical, without subdivisions except for oval-shaped basal bulb. Pharyngeal lumen not cuticularised, valvular apparatus absent. Muscular tissue of basal bulb arranged in bundles. Pharyngeal glands and their orifices indistinct. Nerve ring at 60–65% of pharynx length. Secretory-excretory system not observed. Cardia short.

Reproductive system diorchic with two testes directed anteriorly. Anterior testis outstretched, to the right of intestine, posterior testis antidromously reflexed, situated ventrally. Mature sperm globular to elongated, nucleated, width 5–7 Μm, length 7–13 Μm. Spicules paired, equal, short, arcuate and without capitulum. Spicules evenly cuticularised along entire length, pointed distally. Velum absent. Gubernaculum with straight dorso-caudal apophyses. Rectal gland surrounds distal end of spicules. Two small tubular pre-cloacal supplements and one precloacal seta, 1 Μm long, observed in one specimen. Tail short, conical with blunt tip. Three caudal glands each with separate outlet.

Discussion. Mudwigglus nellyae comb. n. was originally described as possessing two opposed and outstretched testes (perhaps because of their small size), but observation of two paratype specimens revealed the presence of two anteriorly-directed testes, with the posterior testis reflexed. Observation of a female paratype suggests the presence of reflexed ovaries, although the structure of the anterior ovary could not be determined with certainty due to its small size. Thus, Challenger Plateau specimens agree well with the type specimens from Loyalty Basin, New Caledonia, except for some minor inconsistencies. The Challenger Plateau specimens have shorter bodies (275–309 vs 370–420 Μm) and slightly larger amphids (44–50 vs 38–42%cbd). In addition, a precloacal seta and two pre-cloacal supplements were observed in one of the Challenger Plateau specimens, but were not observed in the type specimens from Loyalty Basin. These structures, however, are very small, and the Loyalty Basin specimens are covered by bacteria and detritus, making observations difficult.

Mudwigglus nellyae comb. n. resembles M. patumuka gen. et sp. n. in the shape of the copulatory apparatus and of the tail, but can be differentiated from the latter by its smaller body size (275–420 vs 787–945 Μm), lower values of b (4–5 vs 8–10), fewer pre-cloacal supplements (2 vs 4), and absence of a S-E system and ejaculatory glands. In addition, female M. patumuka gen. et sp. n. specimens all have vaginas directed posteriorly, whereas observation of the paratype female from New Caledonia showed a vagina at right angle with the body surface. These two species appear to have non-overlapping distributions on the continental slope of New Zealand (see Discussion below), which may indicate differences in environmental preference between the two species.

Figures

FIGURE 10. Mudwigglus nellyae (Vincx and Gourbault, 1992) comb. n. A: Entire male; anterior body region of male; C: posterior body region of male. Scale bar: A = 45 Μm; B and C = 20 Μm.