Diplopeltula cuspidiboja, Leduc, Daniel, 2017

Leduc, Daniel, 2017, Four new nematode species (Araeolaimida: Comesomatidae, Diplopeltidae) from the New Zealand continental slope, Zootaxa 4237 (2), pp. 244-264 : 260-263

Diplopeltula cuspidiboja sp. n.

( Figs. 10–12 , Table 2 )

Diagnosis. Diplopeltula cuspidiboja sp. n. is characterised by 1150–2080 µm body length, a striated cuticle, the presence of amphideal plates, a dorsally oriented mouth opening, cup-shaped buccal cavity with pointed ring giving appearance of small teeth, arcuate spicules and gubernaculum with strongly cuticularised apophyses, vulva located at three quarters of body length from anterior, and short conical tail.

Etymology. The species name is derived from the Latin cuspidis (= pointed end) and boja (= collar), and refers to the pointed ring projecting into the buccal cavity of this species.

Holotype. Male (NIWA 115456), collected 20 February 2011 (voyage TAN1103, station 69), crest of Chatham Rise (350 m water depth), 43.331° S, 178.288° E, mean grain size: 55–59 µm, %silt/clay particles: 43–45%.

Paratype. Female (NIWA 115457), collected 17 April 2010 (voyage TAN1004, station 17), Hikurangi Margin (1514 m water depth), 41.6288 °S, 175.8682 °E, mean grain size 9.0 µm, % silt/clay particles: 97.8%.

Description. Male. Colourless cylindrical body tapering slightly towards anterior and posterior ends, with rounded anterior and posterior extremities and conical tail. Cuticle with light transverse striations and sparse somatic setae restricted to anteriormost and posteriormost body regions, 1–2 µm long. Six minute inner labial papilla present on lip region; six outer labial papilla in a separate circle and four cephalic setae situated further posteriorly, 0.3 cbd long. Loop-shaped amphideal fovea and aperture, situated on cuticularised amphideal plate immediately posterior to cephalic setae. Mouth opening oriented dorsally; buccal cavity cup-shaped, lightly cuticularised, with pointed ring giving appearance of small teeth in optical cross-section. Cylindrical pharynx partially surrounding buccal cavity and widening posteriorly without forming a true bulb; pharyngeal tubes not observed. Nerve ring at about 40% of pharynx length from anterior. Secretory-excretory system present, excretory pore slightly posterior to nerve ring; small ampulla and renette cell located immediately anterior to posterior swelling of pharynx. Cardia 5 µm long, partially surrounded by intestine. Reproductive system diorchic with anterior outstretched testis located to the left of intestine and posterior outstretched testis to the right of intestine. Mature sperm cells indistinct. Spicules paired, equal, arcuate, 1.8 cloacal body diameters long, with weakly defined capitulum and short central cuticularised projection (lamella) at proximal end. Gubernaculum surrounding distal ends of spicules, with pair of strongly cuticularised apophyses directed dorso-caudally. Rectal and ejaculatory glands not observed. Tubular precloacal supplements and precloacal seta not observed. Tail short, conical, with rounded distal tip sometimes with sparse lateroventral setae. Three caudal glands with three separate outlets.

Female. Similar to males, but with longer and wider body, and pharynx with well-defined posterior bulb and pharyngeal gland visible. Reproductive system didelphic, with anterior outstretched ovary to the left of intestine and posterior outstretched ovary to the right of intestine. Mature eggs not observed. Spermatheca present in both genital branches, both with numerous sperm. Vulva located at three quarters of body length from anterior. Vaginal glands not observed, proximal portion of vagina uterina surrounded by constrictor muscle.

Differential diagnosis. Diplopeltula cuspidiboja sp. n. resembles other species of the genus with a dorsally oriented mouth opening, namely D. bathmanni , D. belgica , D. dulcis , D. incisa , D. longiloba , D. ostrita , D. striolata and D. tenuis . It is most similar to D. incisa in the body dimensions, presence of amphideal plates, shape and size of the copulatory apparatus, and short conical tail. The new species can be differentiated from D. incisa by the presence of a pointed and lightly cuticularised ring projecting into the buccal cavity (versus unarmed buccal cavity in D. incisa ), and the position of the vulva located further posteriorly (74% versus 62–64% of body length from anterior extremity in D. incisa ).

In the original description of D. incisa by Southern (1914), the buccal cavity is almost terminal and only slightly displaced dorsally in the drawings (although this is not noted in the description), the buccal cavity is cylindrical and without teeth, the amphideal plate is characterised by notches laterally and anteriorly, and the vulva is described as being some distance behind the middle of the body. Subsequent descriptions of the species show some variation in these traits, such as the absence of notches in the amphideal plate ( Vitiello 1972, Warwick 1998), a larger, ovoid buccal cavity ( Gerlach 1950, Warwick 1998), and a mouth situated far dorsally resulting in a displacement of the cephalic setae ( Vitiello 1972). The descriptions of Gerlach (1950), Vitiello (1972), and Warwick (1998), however, all show the vulva to be at 62–64% of body length from the anterior extremity, and none show any buccal cavity armature.

Figures

FIGURE 10. Diplopeltula cuspidiboja sp. n. A: Anterior body region of male; B: anterior body region of female; C: male cephalic region; D: female posterior body region; E: male posterior body region. Scale bar: A = 40 µm; B = 55 µm; C & E = 28 µm; D = 58 µm.

FIGURE 11. Diplopeltula cuspidiboja sp. n. A = Entire male; B: female reproductive system. Scale bar: A = 100 µm; B = 85 µm.

FIGURE 12. Diplopeltula cuspidiboja sp. n. Light micrographs of male. A: Lateral surface view of cephalic region showing amphideal fovea and cephalic setae; B: optical cross-section of cephalic region showing buccal cavity with pointed ring structure. Scale bar = 15 µm.