Paramphimonhystrella glossalga, 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 : 480

Paramphimonhystrella glossalga n. sp.

( Figs 1–4 , Table 1)

Type specimens. Holotype male ( NIWA 89971), collected on 17 April 2007 ( NIWA cruise TAN0705, station 172), Chatham Rise crest (178.6175ºW, 43.5195ºS); water depth: 424 m; silt/clay content: 44.9%; CaCO3 content: 60.9%. One paratype male ( NNCNZ 3160), collected on 20 April 2010 ( NIWA cruise TAN1004, station 58), canyon habitat on southern Hikurangi Margin (175.8977ºE, 41.4080ºS); water depth: 670 m. One paratype female ( NNCNZ 3161), 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 female ( NIWA 89972), collected on 16 April 2010 ( NIWA cruise TAN1004, station 12), canyon habitat on southern Hikurangi Margin (175.7250ºE, 41.5508ºS); water depth: 1350 m. One paratype female ( NIWA 89973), 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

Etymology. The species name is derived from the greek word glossalgos (= very talkative), and refers to the large buccal cavity and double set of lips found in this species.

Description. Males. Body cylindrical, tapering slightly towards anterior extremity. Cuticle ~2.5 µm thick, with annulations beginning at anterior edge of amphid, 1.8–2 µm apart, interspersed with fine striations (the latter not visible under light microscopy) ( Figure 4 A). Somatic setae sparse, 12–18 µm long, arranged irregularly along body. Head tapering anteriorly or with depression just anterior to amphids. Two rings of six lips are present; lips in outermost ring slightly longer (6 µm) than lips in innermost ring (4 µm) ( Figure 4 B). Six setose, jointed inner labial sensillae, 2–3 µm long, situated slightly posterior to base of outer lips and only slightly anterior to six jointed outer labial setae, 4 µm long; six jointed cephalic setae, 7–8 µm long, situated at same level or slightly posterior to outer labial setae. Two rings of sub-cephalic setae; anterior ring consists of sixteen 4–9 µm long setae at level of amphids dorsally and ventrally and slightly posterior to amphids laterally; second ring consists of twelve setae, 13–24 µm long, situated 1–2 cbd posterior to first ring of sub-cephalic setae ( Figure 1 A–E). Amphid large, with round or cryptocircular outline, strongly cuticularised ( Figure 3 A). Buccal cavity large, 28–32 µm deep, with ~7 µm wide cylindrical anterior portion and funnel-shaped posterior portion, strongly cuticularised; posterior portion surrounded by pharyngeal tissue. Pharynx muscular, widening posteriorly but not forming true bulb. Cardia small but distinct, surrounded by intestine tissue. Nerve situated at 55% of pharynx length from anterior. Secretory-excretory system not observed.

Male reproductive system diorchic with outstretched testes. Both testes situated to the right of intestine. Mature sperm cells oval-shaped, ~8×6–7 µm, nucleated. Spicules joined distally, 1.0–1.1 abd long, heavily cuticularised, slightly bent, widest in middle portion, with rounded proximal end and pointed distal end ( Figure 1 G, 2A); lamella present, no gubernaculum. Pre-cloacal supplements absent. Tail conico-cylindrical, with a few scarce irregularly arranged setae. One sub-terminal seta, 18–20 µm long and two terminal setae, 20–25 µm long ( Figure 1 F, H). Three caudal gland; one gland conspicuously larger than other two.

Females. Similar to males, but with smaller head diameter, slightly shorter cephalic setae, and smaller amphids. Reproductive system monodelphic with anterior branch outstretched, to the left of intestine; postvulvar sac long, separated from uterus by muscular sphincter ( Figure 2 C), apparently divided into three compartments and with numerous sperm cells ( Figure 2 B). Mature egg 66–73×22–29 µm. Vulva situated mid-body. Granular vaginal glands present; distinctive hammer-shaped cuticularised piece situated ventrally and immediately posterior to vagina, 17 µm long and 3 µm wide in narrow portion, flanked on either side by vaginal glands ( Figure 2 C, 3C).

Diagnosis. Paramphimonhystrella glossalga n. sp. is characterised by two rings of six lips, large buccal cavity with cylindrical anterior portion and funnel-shaped posterior portion, large and heavily cuticularised amphids, two rings of twelve and sixteen sub-cephalic setae, tail with one sub-terminal seta and two terminal setae, males with short heavily cuticularised spicules joined distally, females with large postvulvar sac and hammer-shaped cuticularised piece immediately posterior to vagina.

Differential diagnosis. Paramphimonhystrella glossalga n. sp. resembles P. s i n i c a in the size and shape of the buccal cavity and amphids, but differs most markedly from the latter in the number of sub-cephalic setae (two rings of 12–16 setae in P. glossalga n. sp. vs two rings of ten setae in P. s i n i c a), shape of the spicules (heavily cuticularised and thickest in middle portion vs slender), number of terminal setae (two vs three), and presence of conspicuous hammershaped cuticularised piece immediately posterior to vagina (absent in P. s i n i c a). The latter trait is only found in one other species of the genus, viz., P. scutula n. sp. P. glossalga n. sp. differs most markedly from P. s cu t ul a n. sp. in the size and number of head sensillae, size and shape of the buccal cavity, number of sub-cephalic setae, and shape of the spicules.

Figures

FIGURE 1. Paramphimonhystrella glossalga A: Lateral surface view of male head; B: lateral view of male head; C: lateral view of female head; D: female anterior body region; E: male anterior body region; F: male posterior body region; G spicule; H: female posterior body region. Scale bar: A, B, and C = 30 µm; D, E, F, and H = 48 µm; G = 15 µm.

FIGURE 2. Paramphimonmhystrella glossalga A: entire male; B: female reproductive system; C: close-up of female vulva showing hammer-shaped cuticularised piece. Scale bar: A and B = 100 µm; C = 30 µm.

FIGURE 3. Paramphimonmhystrella glossalga Light micrographs. A: Lateral view of male head, showing lips, buccal cavity, and cuticularised outline of amphid; B: ventral view of female head showing lips, buccal cavity, and ingested material; C: lefthand side view of vulva, showing hammer-shaped cuticularised piece; D: gut content of male, showing single-celled eukaryotic organism. Arrow shows position of vulva opening. Scale bar = 10 µm.

FIGURE 4. P aramphimonhystrella glossalga Scanning electron micrographs. A: Lateral view of male head; B: close-up view of male lips. Scale bar: A = 10 µm; B = 5 µm.