Sabatieria pumila, Leduc, Daniel, 2013

Leduc, Daniel, 2013, Seven new species and one new species record of Sabatieria (Nematoda: Comesomatidae) from the continental slope of New Zealand, Zootaxa 3693 (1), pp. 1-35 : 26-28

Sabatieria pumila sp. n.

( Figs 16-18 , Table 4)

Material examined. Holotype male (NIWA 865999), collected 5 October 2001, Chatham Rise crest (350 m water depth), 43.4333°S, 178.5000°E. Characteristics of surface sediment layer (0–5 mm): mostly fine sand (35.7%), silt/ clay (33.0%), and very fine sand (23.5%); calcium carbonate content: 40.5%; total organic matter content: 4.5%; chloroplastic pigment concentration: 3359 ng /gDW sediment. Three male and three female paratypes (NIWA 866000), same data as holotype.

Etymology. The species name is derived from the latin pumilus (= dwarfish, little), and refers to the small size of this species relative to most other species of the genus.

Description. Male Body short, cylindrical, tapering slightly towards anterior extremity. Cuticle with transverse rows of dots, lateral differentiation consisting of transverse rows of larger dots. Two dorso- and two ventro-lateral rows of short, sparse somatic setae, some associated with inconspicuous, elongated hypodermal glands ( Fig. 18 A). Head slightly set-off by depression at level of fovea amphidialis. Six minute inner and outer labial papillae and four short cephalic setae. Anterior portion of buccal cavity small, cup-shaped, posterior portion narrow. Fovea amphidialis spiral, 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 widening from middle of region of pharynx towards posterior, not forming a true bulb, cardia short, 5 µm long. Nerve ring at about middle of pharynx length. Secretory-excretory system present, cellular body of ventral gland at level of intestine, pore situated 0.5–1.0 cbd posterior to nerve ring. Intestine wall with numerous small, colourless granules.

Reproductive system diorchic with outstretched testes. Anterior testis on left of intestine, posterior testis on right of intestine. Mature sperm cells elongated, nucleated, 5–6 µm diameter, 12–13 µm long. Spicules paired, equal, arcuate, 1.5–2.0 abd long, without capitulum, and with central cuticularised projection (lamella) extending from proximal end over one third to half of spicule length. Velum present. Distal end of spicules pointed, with ventral hook and with small central cuticularised projection ( Figs 16 C, E). Gubernaculum with pair of straight dorso-caudal apophyses. Rectal gland surrounds gubernacular apophyses and distal portion of spicules. Three pairs of ejaculatory glands present anterior to spicules. Eight or nine small tubular pre-cloacal supplements, one precloacal seta. Tail conico-cylindrical with slightly clavate tip. Several short caudal setae and three short terminal setae. Three caudal glands and spinneret present.

Female Similar to male, but with wider body and slightly smaller fovea amphidialis, 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 spermatheca present. Vulva situated mid-body. Vaginal glands not observed, pars proximalis vaginae surrounded by constrictor muscle.

Diagnosis and relationships. Sabatieria pumila sp. n. is characterised by a combination of having a relatively small body length (725–1009 µm), cuticle with lateral differentiation consisting of rows of larger dots, short cephalic setae (2–3 µm), fovea amphidialis with 3.5 turns, spicules with distal hook and short distal lamella, and 8– 9 precloacal supplements.

Sabatieria pumila sp. n. belongs to the pulchra group and resembles S. pisinna and S. propisinna due to its small body length and short cephalic setae. Sabatieria pumila sp. n. can be differentiated from S. propissina in the structure of the fovea amphidialis (3.5 vs 2.25 turns in S. propisinna ), length of the spicules (1.5–2.0 vs 1.3–1.4 abd), structure of the spicules (distal end with hook and short lamella vs no hook and no lamella), and structure of the gubernaculum (not surrounding spicules in S. pumila sp. n. vs surrounding spicules in S. propissina ). S. pumila sp. n. differs from S. pisinna in cuticle ornamentation (lateral differentiation present vs absent in S. pisinna sp. n.), length of spicules (1.5–2.0 vs 1.3 abd), structure of the spicules (distal end with hook and short lamella vs hook absent and lamella extending over half of spicule length), and presence of pre-cloacal supplements (vs absent). Muthumbi et al. (1997) described Sabatieria specimens from the Indian Ocean showing several similarities with S. pisinna , such as small body length, short cephalic setae, and absence of pre-cloacal supplements. Their specimens, however, were characterised by cuticle with lateral differentiation of larger dots (vs no differentiation in original description by Vitiello (1970)), and curved gubernaculum surrounding distal end of spicules (vs straight gubernaculum not surrounding spicules in original description). Muthumbi et al. (1997) argue that the lateral differentiation of the cuticle may have been overlooked in the original description of the species by Vitiello (1970), even though the latter author noted lateral differentiation in the cuticle of S. propissina (Vitiello, 1976) . The specimens described by Muthumbi et al. (1997) may, therefore, belong to a distinct species.

Figures

FIGURE 16. Sabatieria pumila sp. n. A: Male anterior region; B: female anterior region; C: male copulatory apparatus; D: female tail; E: male posterior region. Scale bar = 20 µm.

FIGURE 17. Sabatieria pumila sp. n. A: Entire male; B: female reproductive system. Scale bar = 50 µm.

FIGURE 18. Sabatieria pumila sp. n. Light micrographs. A: Male hypodermal glands, lateral view; B: male copulatory apparatus. Arrows show the position of the pre-cloacal supplements. Scale bar: A = 10 µm, B = 14 µm.