Sabatieria bitumen

Sabatieria bitumen

(Figs 1–3, Table 1)

Material examined. Five males, four females (NIWA 865986), collected 6 April 2007, southwest Chatham Rise (1240 m water depth), 44.4864°S, 177.1407°E. Characteristics of surface sediment layer (0–5 mm): mostly silt/ clay (82.9%), with very fine sand (9.4%), and fine sand (7.7%); calcium carbonate content: 38.4%; total organic matter content: 1.9%; chloroplastic pigment concentration: 3501 ng /gDW sediment.

Description. Male Body cylindrical, tapering slightly towards anterior extremity. Cuticle with transverse rows of dots, lateral differentiation consisting of larger, irregularly-spaced dots. Two dorso- and two ventrolateral rows of short, sparse somatic setae. Head set-off by constriction immediately posterior to cephalic setae. Six inner labial papillae, six outer labial papillae, and four short cephalic setae. Anterior portion of buccal cavity cup-shaped, lightly cuticularised at base, posterior portion narrow. Fovea amphidialis spiral, 3.0–3.5 turns, located immediately posterior to cephalic setae. Marginal tubes arising from base of buccal cavity and extending to posterior end of pharynx. Pharynx gradually swelling towards posterior, not forming true bulb, cardia short, 5–10 µm long. Nerve ring near middle of pharynx. Secretory-excretory system present, cellular body of ventral gland near level of cardia, pore situated 0.5–1.0 cbd posterior to nerve ring. Intestine wall with numerous small, colourless granules, with differentiation of rounded cells containing more densely packed granules in anterior portion (Figs 2 B and 3C), and clusters of clear circular inclusions in posterior portion of intestine (Fig. 2 D).

Reproductive system diorchic with outstretched testes. Anterior testis to left of intestine and posterior testis to right of intestine. Mature sperm cells elongated, length 14–17 m and diameter 7– 9 m. Spicules paired, equal, arcuate, 1.4–1.6 abd long, without capitulum, distal hook and with central cuticularised projection (lamella) extending from proximal end over one quarter of spicule length. Velum present. Gubernaculum with pair of straight caudal apophyses with broad base. Rectal gland surrounds gubernacular apophyses and anterior portion of spicules. Three to four pairs of ejaculatory glands present anterior to spicules. Eight to ten small tubular pre-cloacal supplements, one pre-cloacal seta. Tail conical, gradually tapering, with rounded tip, several short caudal setae and three short terminal setae. Three caudal glands and spinneret present.

Female Similar to male, but with slightly smaller amphid, 3.0–3.25 turns. Reproductive system didelphic, opposed, outstretched, with anterior branch to the left of intestine and posterior branch to the right of intestine. Oval-shaped spermathecae present, containing numerous sperm cells. Vulva situated mid-body. Granular vaginal glands present, pars proximalis vaginae surrounded by constrictor muscle.

Discussion. The specimens examined here closely resemble the description of Botelho et al. (2007) based on specimens from the South Atlantic Ocean (750–1650 m water depth), although the Chatham Rise specimens possess slightly longer spicules (46–51 vs 40–46 m) and longer tails (88–97 vs 67–81 µm). Sabatieria bitumen was among the most common species in a study of the nematode fauna on the continental slope of New Zealand, representing 2.5% of identified specimens (Leduc et al. 2012). It was also recorded from the Gulf of Càdiz, Northeast Atlantic, in the vicinity of the Darwin mud volcano (~ 1100 m water depth; Pape et al. 2011).