Mudwigglus macramphidum

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 : 359

Mudwigglus macramphidum gen. et sp. n.

( Figs 4–6 , Table 1)

Type specimens. Holotype male, collected on 20 February 2011 ( NIWA cruise TAN1103, station 69), central Chatham Rise (43.331° S, 178.288° E), water depth: 350 m, sediment depth: 1–5 cm (NIC 865978). Three paratype males and two paratype females, same data as holotype (NIC 865979).

Etymology. The species name is derived from the Greek word makros (= long) and refers to the elongated shape of the fovea amphidialis in this species.

Description. Males. Cylindrical body, colourless, tapering slightly towards both extremities. Cuticle 0.8 Μm thick, with annuli beginning posterior to cephalic setae to near tail tip, situated 2–3 Μm apart, no lateral differentiation. Two subventral and two subdorsal rows of short (1 Μm long), sparse somatic setae extending from posterior edge of fovea amphidialis to level of cloaca. Six elongated, nucleated hypodermal glands surrounding pharynx slightly anterior to nerve ring ( Figure 4 A, E). Hypodermal glands not observed in main part of body. Lateral chords with honeycomb-like appearance and clusters of small, elongated inclusions always situated ventrally ( Figure 4 F). Three pairs of subventral setae and 2–3 pairs of subdorsal setae on tail. Terminal setae absent.

Labial region rounded, not set off. Inner labial sensillae not observed. Six minute outer labial sensillae and four cephalic setae, 1Μm long. Subcephalic setae absent. Fovea amphidialis an elongated loop, with cuticularised outline, 3.5 times longer than wide. Buccal cavity short, cylindrical, lightly cuticularised, separated from anterior extremity by narrow, 4 Μm long mouth opening surrounded by bulge of inner portion of lip region. 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 present, renette cell at level with intestine, ampulla and pore at level of pharyngeal bulb or slightly anterior. Pore opening surrounded by small but distinct cuticularised ring ( Figure 6 B). 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 4–6 Μm, length 6–10 Μm. Spicules paired, equal, short, arcuate. Weak capitulum visible in some specimens depending on viewing angle. Spicules evenly cuticularised along entire length, pointed distally. Velum absent. Gubernaculum without apophyses. Rectal gland surrounds spicules and gubernaculum. Two pairs of large, nucleated ejaculatory glands situated anteriorly to spicules ( Figure 4 H). Two small tubular pre-cloacal supplements, one pre-cloacal seta, 1–2 Μm long. Tail conico-cylidrical with slightly clavate tip. Caudal glands and spinneret not observed.

Females. Similar to males, but with slightly smaller fovea amphidialis and longer tail. Somatic setae present. Female reproductive system didelphic, amphidelphic with reflexed ovaries. Anterior ovary located to the right of intestine, posterior ovary to the left of intestine. Spermathecae not observed. Vulva located midbody. Vagina at right angle with body surface ( Figure 6 C). Pars proximalis vaginae surrounded by constrictor muscle.

Diagnosis and relationships. Mudwigglus macramphidum gen. et sp. n. is characterised by the long fovea amphidialis, short cylindrical buccal cavity, presence of six hypodermal gland surrounding anterior portion of pharynx, gubernaculum without apophyses, vagina at right angle to body surface, and conicocylindrical tail without terminal setae. M. macramphidum gen. et sp. n. can be differentiated from all other species of the genus based on the shape of the fovea amphidialis (3.5 vs <2.5 times longer than wide in other species), shape of buccal cavity (cylindrical vs funnel-shaped), gubernaculum without apophyses (present in other species), straight vagina (directed posteriorly in other species), and absence of terminal setae (present in other species).

Figures

FIGURE 4. Mudwigglus macramphidum gen. et sp. n. A: Male anterior region; B: male head surface view; C: male head, cross section view; D: female head, surface view; E: female anterior region; F: female lateral chord, left hand side view; G: female tail; H: male posterior region. Scale bar = 25 Μm.

FIGURE 5. Mudwigglus macramphidum gen. et sp. n. A: Entire male; B: entire female. Scale bar = 50 Μm.

FIGURE 6. Mudwigglus macramphidum gen. et sp. n. light micrographs. A: Male, anterior portion of pharynx, showing buccal cavity and hypodermal glands (bottom); B male, posterior portion of pharyx and anterior portion of intestine, showing pharyngeal bulb and ventral gland; C: vulva. Arrow points to cuticularised opening of secretory-excretory system. Scale bar: A and B = 20 Μm; C = 16 Μm.