Southerniella parasimplex Leduc, 2017, sp. n.

Southerniella parasimplex sp. n.

(Figs. 7–9, Table 2)

Diagnosis. Southerniella parasimplex sp. n. is characterised by 840–1130 µm body length, cephalic setae 0.3 cbd long, amphids 0.5–0.6 cbd wide and situated immediately posterior to the cephalic setae, buccal cavity ~12 µm deep, secretory-excretory system with three renette cells, presence of progaster consisting of densely granulated cells, conicocylindrical tail, female with two outstretched ovaries and single anterior spermathecum, and male with outstretched anterior testis and reflexed posterior testis directed anteriorly, and gubernaculum surrounding spicules distally and with apophyses directed dorsally.

Etymology. The species name refers to the similarity between the new species and Southerniella simplex. Holotype. Male (NIWA 115454), collected 15 April 2010 (voyage TAN1004, station 4), Hikurangi Margin (1046 m water depth), 41.6837 °S, 175.6642 °E, mean grain size: 12 µm, %silt/clay particles: 94.7%.

Paratype. Female (NIWA 115455), same data as holotype.

Description. Males. Colourless cylindrical body tapering slightly towards anterior end, with rounded anterior extremity and conicocylindrical tail. Cuticle with faint transverse striations; no somatic setae observed. Walls of numerous epidermal cells visible throughout length of body; content of epidermal cells transparent. Cephalic region narrow and set off from rest of body. Inner and outer labial sensilla not observed; four cephalic setae, 0.3 cbd long. Subcephalic setae absent. Circular amphideal fovea and aperture, situated immediately posterior to cephalic setae. Buccal cavity cylindrical, narrow, ~12 µm deep, weakly cuticularised, surrounded by pharyngeal tissue. Cylindrical pharynx with anteriormost portion (corpus) thinner than the rest of pharynx, and with slight posterior bulb; pharyngeal tubes present but difficult to observe. Nerve ring at ~60% of pharynx length from anterior. Secretory-excretory system with three renette cells situated immediately posterior to pharynx; pore not observed. Anteriormost portion of intestine differentiated as enlarged, densely granulated cells surrounding cardia (progaster). Reproductive system diorchic with anterior outstretched testis located to the left of intestine and anteriorly oriented and reflexed posterior testis situated ventrally relative to intestine. Mature sperm cells globular, 5 × 7 µm, with oval nuclei. Spicules paired, equal, strongly bent, almost L-shaped, 1.2 cloacal body diameters long, without capitulum. Gubernaculum surrounding distal ends of spicules, with pair of apophyses directed dorsally and parallel with proximal end of spicules. Four rectal glands present; two glands situated laterally and slightly anteriorly to spicules, one gland situated dorsally relative to spicules, and one gland immediately posterior to spicules. Three pairs of ejaculatory glands also present further anteriorly. Precloacal supplements and precloacal seta not observed. Tail conicocylindrical, with short cylindrical terminal portion. Three caudal glands and spinneret present.

Species Diplopeltula cuspidiboja sp. n. Southerniella parasimplex sp. n. Female. Similar to male, but with walls of epidermal cells not as conspicuous, slightly smaller amphid, pharyngeal tubes conspicuous in anterior half of pharynx, and slightly shorter tail. Reproductive system didelphic, with anterior outstretched ovary to the left of intestine and posterior outstretched ovary to the right of intestine. Single anterior spermathecum present with several sperm cells. Vulva located slightly posterior to mid-body. A single posterior granular vaginal gland present, proximal portion of vagina uterina surrounded by constrictor muscle.

Differential diagnosis. Southerniella parasimplex sp. n. is most similar to S. simplex in having relatively large amphids located immediately or almost immediately posterior to the cephalic setae, as well as a relatively short buccal cavity. Southerniella parasimplex sp. n. can be differentiated from S. simplex by the orientation of the gubernacular apophyses (dorsally-directed and parallel to spicules in S. parasimplex sp. n. versus dorso-caudally directed and perpendicular to spicules in S. simplex), and the shape of the tail (conicocylindrical in S. parasimplex sp. n. versus conical in S. simplex). The new species is also similar to S. conicauda in having a relatively short buccal cavity but can be differentiated from the latter by the presence of a gubernaculum (absent in S. conicauda) and the shape of the tail (conicocylindrical in S. parasimplex sp. n. versus usually conical and sometimes conicocylindrical in S. conicauda).

Remarks. The progaster in Southerniella conicauda, Intasia amblynema and Intasia lympha usually comprises four enlarged and non-granular cells. Progaster cells in Southerniella parasimplex sp. n. have an unusual granulated appearance, and their number could not be determined with certainty. Jensen (1991) noted the presence of a progaster in other genera of the Order Araeolaimida, namely Cylindrolaimus de Man, 1880 (Diplopeltidae) and Bodonema Jensen, 1991 (Bodonematidae), as well as in some Monhysteridae.