Paramphimonhystrella barbula, Leduc, Daniel, 2014

Leduc, Daniel, 2014, Four new Paramphimonhystrella species (Nematoda: Xyalidae) from the continental slope of New Zealand, Zootaxa 3814 (4), pp. 478-494 : 484-488

Paramphimonhystrella barbula n. sp.

( Figs 5 and 6 , Table 1)

Type specimens. Holotype male ( NIWA 89974), collected on 15 April 2010 ( NIWA cruise TAN1004, station 4), open slope habitat on southern Hikurangi Margin (175.6642ºE, 41.6837ºS); water depth: 1046 m. One paratype male ( NNCNZ 3165), same data as holotype. Two paratype males ( NIWA 89975), collected on 21 April 2010 ( NIWA cruise TAN1004, station 72), open slope habitat on southern Hikurangi Margin (176.1958ºE, 41.3657ºS); water depth: 985 m. One paratype male ( NNCNZ 3166), collected on 22 April 2010 ( NIWA cruise TAN1004, station 76), open slope habitat on southern Hikurangi Margin (175.6500ºE, 41.6833ºS); water depth: 1282 m. One paratype female ( NIWA 89976), collected on 5 October 2001 ( NIWA cruise TAN0116, station U2582), Chatham Rise crest (178.5000ºE, 43.4333ºS); water depth: 350 m; silt/clay content: 37.5%; CaCO3 content: 61.6%.

Etymology. The species name is the diminutive of the latin word barba (= beard) and refers to the relatively short sub-cephalic setae in this species.

Species P. glossalga n. sp. P. barbula n. sp.

Males Females Males Female Holotype Paratype Paratypes Holotype Paratypes Paratype n 1 3 4 1 L 1402 1376 1012-1309 991 958-1086 1117 Description. Males. Body cylindrical, tapering slightly towards anterior extremity. Cuticle ~0.6–0.8 µm thick, with fine striations ~1 µm apart beginning immediately anterior to amphids ( Figure 5 A). Somatic setae short and sparse, irregularly arranged. Head tapering anteriorly or with depression just anterior to amphids. Inner labial sensillae not observed; six outer labial setae, 2–3 µm long, situated immediately anterior to four cephalic setae of same length. Two rings of sub-cephalic setae; anterior ring consists of ten 3–6 µm long setae at level of amphids dorsally and ventrally and slightly posterior to amphids laterally; second ring consists of ten setae of same length situated 0.5–1.0 cbd posterior to first ring of sub-cephalic setae ( Figure 5 A–E). Amphids large, with oval or ovoid outline, lightly cuticularised. Buccal cavity 9–11 µm deep, 1–2 µm wide, with cylindrical anterior portion and funnel-shaped posterior portion, lightly cuticularised; posterior portion surrounded by pharyngeal tissue. Pharynx muscular, widening posteriorly but not forming true bulb. Cardia elongated, with posterior end surrounded by intestine tissue and a pair of gland-like cells dorsally and ventrally ( Figure 5 D, E). Nerve situated at middle of pharynx. Secretory-excretory system not observed.

Male reproductive system diorchic with outstretched testes; in some specimens only the anterior or posterior testis is visible. Both testes (when observed) situated to the right of intestine. Mature sperm cells small and rodshaped, ~1×6 µm ( Figure 5 H). Spicules slender, 2.7–3.6 abd long, lightly cuticularised, with blunt proximal end and pointed distal end ( Figure 5 G); gubernaculum present, thin, parallel to spicules, with fine lateral crurae. Precloacal supplements absent. Tail conico-cylindrical, with one pair of sub-ventral and one pair of sub-dorsal setae ~2 cbd posterior to cloaca and single dorsal seta on cylindrical portion. Two terminal setae, 7–10 µm long. Three caudal gland; one gland conspicuously larger than other two and giving tail a swollen appearance ( Figure 5 G and 6A).

Species P. scutula n. sp. P. echinocauda n. sp.

Males Females Males Holotype Paratype Paratypes Holotype Female. Similar to males, but with slightly smaller amphids. Reproductive system monodelphic with outstretched anterior branch to the left of intestine; postvulvar sac present, consisting of numerous clear cells; sperm cells observed in uterus but not postvulvar sac ( Figure 6 B). Mature egg 118×19 µm. Vulva situated mid-body. Granular vaginal glands not observed; pars proximalis vaginae surrounded by constrictor muscle.

Diagnosis. Paramphimonhystrella barbula n. sp. is characterised by narrow buccal cavity with funnel shaped posterior portion, oval-shaped amphids, two rings of ten sub-cephalic setae, conico-cylindrical tail with swollen appearance due to conspicuously enlarged caudal gland, and males with long slender spicules and small gubernaculum parallel to the spicules.

Differential diagnosis. Paramphimonhystrella barbula n. sp. is similar to P. elegans in the shape of the buccal cavity, size and shape of the amphids, number and arrangement of sub-cephalic setae, and shape of the tail. It differs from the latter in body size (991–1117 µm in P. barbula n. sp. vs 1286–1916 µm in P. elegans ), length of cephalic setae (2–3 vs 4–6 µm), length of the spicules (2.7–3.6 vs 0.7–1.0 abd), and presence of gubernaculum (vs absent).

Figures

FIGURE 5. Paramphimonhystrella barbula A: Lateral surface view of male head; B: lateral view of male head; C: lateral view of female head; D: male anterior body region; E: female anterior body region; F: female posterior body region; G: male posterior body region; H: sperm. Scale bar: A – C, F – H = 20 µm; D and E = 27 µm.

FIGURE 6. Paramphimonhystrella barbula A: Entire male; B: entire female. Scale bar = 50 µm.