Sabatieria challengerensis, 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 : 5-11

Sabatieria challengerensis sp. n.

( Figs 4–5 , Table 1)

Material examined. Holotype male (NIWA 865987), collected 5 June 2007, western Challenger Plateau (532 m water depth), 40.8814°S, 170.8603°E. Characteristics of surface sediment layer (0–5 mm): mostly silt/clay (67.6%), with fine sand (15.1%) and very fine sand (11.4%); calcium carbonate content: 56.0%; total organic matter content: 2.1 %; chloroplastic pigment concentration: 1344 ng /gDW sediment. Three male and four female paratypes (NIWA 865988), same data as holotype.

Etymology. This species is named after Challenger Plateau, the type locality.

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 ventro-lateral rows of short, sparse somatic setae. Head set-off by depression at level of 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 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 at level of intestine, 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.

Reproductive system diorchic with outstretched testes. Anterior testis on left of intestine, posterior testis on right of intestine; one specimen with opposite arrangement. Mature sperm cells globular, nucleated. Spicules paired, equal, arcuate, 1.3–1.8 abd long, without capitulum, and with central cuticularised projection (lamella) extending from proximal end over one quarter to one third of spicule length. Gubernaculum with pair of straight caudal apophyses with narrow base. Rectal gland surrounds gubernacular apophyses. Two to three pairs of ejaculatory glands present anterior to spicules. Five to eight small tubular pre-cloacal supplements, one pre-cloacal seta. Tail short, with cylindrical or slightly tapering proximal portion and blunt, rounded distal portion, several short caudal setae and three short terminal setae. Three caudal glands and spinneret present.

Female Similar to males, but with slightly smaller amphid, 2.5–3.0 turns. Reproductive system didelphic, opposed, outstretched, with anterior branch to the left of intestine and posterior branch to the right of intestine.

Spermatheca not observed. Vulva situated slightly pre-median. Granular vaginal glands present, pars proximalis vaginae surrounded by constrictor muscle.

Diagnosis and relationships. Sabatieria challengerensis sp. n. is characterised by a combination of having cuticle with lateral differentiation consisting of larger, irregularly-spaced dots, short cephalic setae (2 m), large fovea amphidialis (73–85% cbd) with 3 turns, short arcuate spicules without a distal hook, 5–8 small tubular precloacal supplements, and a short tail (1.8–2.7 abd) with a cylindrical or slightly tapering proximal portion and a blunt, rounded distal portion.

Sabatieria challengerensis sp. n. belongs to the praedatrix group. Most Sabatieria species of this and other Sabatieria groups are characterised by conical (i.e., gradually tapering) or conico-cylindrical tails (i.e., with conical proximal portion and cylindrical distal portion). In contrast, S. challengerensis sp. n. is characterised by a tail similar in shape to S. subrotundicauda , i.e., with a cylindrical or only slightly tapering proximal portion and a blunt, rounded distal portion. Sabatieria challengerensis sp. n. can be differentiated from S. subrotundicauda by the structure of the spicules (distal hook absent vs present in S. subrotundicauda ), and structure of the female reproductive system (ovaries outstretched vs reflexed in S. subrotundicauda ).

Short conical tails superficially similar in shape to the tails of S. challengerensis sp. n. and S. subrotundicauda are present in S. dorylaimopsoides , S. conicauda , S. spiculata , S. paraspiculata , and S. bitumen . In addition to the difference in tail shape, S. challengerensis sp. n. can be differentiated from S. dorylaimopsoides by the presence of outstretched ovaries (reflexed in S. dorylaimopsoides ), from S. conicauda by the greater values of c (17–21 vs 14– 16), longer spicules (40–46 vs 36–37 µm, 1.2 vs 1.3–1.8 abd), and length of gubernacular apophyses (11–12 vs 16 µm), from S. spiculata by smaller body size (1060–1279 vs 1505–1860 µm), absence of dorsal tooth (present in S.

spiculata ), and fewer pre-clocal supplements (5–8 vs 10–14), from S. paraspiculata by greater values of a (33–42 vs 21) and position of the secretory-excretory pore (posterior to nerve ring vs at level of nerve ring in S. paraspiculata ), and from S. bitumen by the absence of a distal hook on the spicules (present in S. bitumen ).

Species Sabatieria bitumen Sabatieria challengerensis sp. n.

Males Females Males Females Holotype Paratypes Paratypes

n 5 4 3 4

L 1267–1415 1305–1537 1095 1060–1213 1250–1279

a 32–39 28–37 38 33–42 35–41

b 7 7–8 7 7 6–7

c 14–15 15–16 18 18–19 17–21

Head diam.* 13– 14 14–15 11 10–12 13–14

Mouth diam. 4 4 3 3–4 4–6

Length of cephalic setae 2 2 2 1–2 2

Amphid height 9–10 7–8 10 9–12 7–8

Amphid width 9–11 8–9 11 11 8–9

Amphid width/cbd (%) 61–77 47–56 73 73–85 50–60

Amphid from anterior end 7–8 7–9 6 4–5 6–7

Nerve ring from anterior end 85–105 96–113 88 80–95 92–105

Nerve ring cbd 28–31 31–32 26 25–29 28–33

Excretory pore from anterior end 109–133 112–143 109 88–114 109–130

Pharynx length 177–194 176–218 166 150–181 177–197

Pharynx cbd 32–35 34–39 27 27–32 31–37

Pharyngeal bulb diam. 21–24 24–27 19 19–21 22–26

Max. body diam. 34–39 35–50 29 29–35 31–37

Spicule length 46–51 - 40 40–46 -

Gubernacular apophyses length 14–16 - 11 11–12 -

Anal body diam. 31–35 30–36 26 24–34 28–34

Tail length 88–95 88–97 60 58–68 60–75

Tail length/abd 2.6–3.1 2.5–3.0 2.3 1.9–2.7 1.8–2.6

V - 671–763 - - 594–632

% V - 50 –51 - - 47–49

Vulval body diam. - 33–48 - - 30–35

*at level of cephalic setae.

Figures

FIGURE 4. Sabatieria challengerensis sp. n. A: Male anterior region; B: lateral surface view of female head; C: lateral surface view of male head; D: female tail; E: male posterior region. Scale bar: A, D, and E = 40 µm; B and C = 20 µm.

FIGURE 5. Sabatieria challengerensis sp. n. A: Entire male; B: female reproductive system. Scale bar = 60 µm.