Aegialoalaimus magnus, Leduc, 2023

Leduc, Daniel, 2023, New nematode species and genera (Nematoda: Chromadorea) from cold seeps on Hikurangi Margin, New Zealand, European Journal of Taxonomy 856, pp. 1-45 : 29-34

Aegialoalaimus magnus sp. nov.

urn:lsid:zoobank.org:act:4D4BD1F6-70E8-4E2B-BF6C-530389C772AA

Figs 13–15 , Table 6

Diagnosis

Aegialoalaimus magnus sp. nov. is characterized by body length 2.8–3.3 mm, papilliform cephalic sensilla, amphids with strongly cuticularized outline and central region with pitted appearance, radiating, cuticularized processes surrounding junction of pharyngostome and cheilostome, secretory-excretory pore located at or near level of nerve ring and ventral gland well posterior to cardia, spicules 1.4–1.6 cloacal body diameters long, well-developed gubernacular apophyses, 11–12 inconspicuous precloacal supplements, and conical tail 2.8–3.5 cloacal or anal body diameters long.

Differential diagnosis

The new species differs from all other species of the genus in the longer body (2.8–3.3 vs <2.0 mm in all other species), gubernaculum with conspicuous apophyses (vs apophyses absent in all other species) and greater number of precloacal supplements (11–12 vs 0–8 in all other species).

Etymology

The species name is derived from the Latin ʻ magnus ʼ meaning ʻlargeʼ, ʻgreatʼ and refers to the relatively large size of the species.

Material examined

Holotype NEW ZEALAND • ♂; Hikurangi Margin , Mungaroa cold seep site; 41.9376° S, 175.3110° E; 2075 m water depth; collected on 7 Jul. 2019; sandy mud sediment (97% silt/clay, mean particle size 19 µm), voyage TAN1904, station 18; NIWA154918 .

Paratypes NEW ZEALAND • 2 ♀ ♀; same collection data as for holotype; NIWA 154920 • 1 ♂; Glendhu cold seep site; 41.7695° S, 176.0882° E; 1993 m depth; collected 10 Jul. 2019; sandy mud sediment (88% silt/clay, mean particle size 27 µm), voyage TAN1904, station 40; NIWA 154919 .

Type habitat and locality

New Zealand continental slope, Hikurangi Margin, Mungaroa and Glendhu cold seeps.

Description

Male

Body colourless, cylindrical along most of its length, tapering slightly towards both extremities. Cuticle with fine transverse striations without lateral differentiation. Body pores and epidermal glands absent. A few sparse, short somatic papillae, 1 µm long, present in anterior pharyngeal region. Cephalic region slightly rounded; lip region poorly developed, continuous with body contour, lips fused. Inner labial papillae not observed; six short outer labial papillae, <1 µm long, located slightly anterior to four slightly longer cephalic papillae, 1–1.5 µm long. Subcephalic setae absent. Amphideal fovea circular with strongly cuticularized outline and central region with pitted appearance, situated well posterior to cephalic sensilla, 0.6–0.7 cbd from anterior end. Ocelli absent. Oral opening termina. Cheilostome is a narrow tube 7–8 µm long; pharyngostome 4–6 µm wide, indistinguishable from the cuticularised lumen of the pharynx. Six short and cuticularized radiating processes surrounding junction of pharyngostome and cheilostome, S-shaped. Pharynx divided into two sections: anterior tubular part and posterior (basal) bulb. Tubular part of the pharynx is 163–196 µm long, 4–8 µm wide, with irregular contour, surrounded by thin sheath of non-muscular tissue. Posterior bulb muscular, oval-shaped, surrounded by six elongated glands with ducts extending anteriorly, each comprised of multiple nucleated cells. Pharyngeal glands sometimes visible. Nerve ring located at 59–67% of pharynx length from anterior. Secretoryexcretory system present; pore located at or immediately posterior to level of nerve ring, ampulla small, renette cell located 1.5–2.5 cbd posterior to pharyngeal bulb. Cardia ca 15–18 µm long, partially surrounded by intestine.

Reproductive system diorchic with with two anteriorly-directed testes both located ventrally or to the left of intestine; anterior testis outstretched, posterior testis reflexed. Sperm cells globular, 13–17 × 9–13 µm, of similar shape and dimensions in both testes. Spicules paired, equal, strongly cuticularized, arcuate and 1.4–1.6 cloacal body diameters long; tapered distal end swollen proximal end (capitulum). Gubernaculum dorso-caudal apophyses slightly bent distally. Ejaculatory and rectal glands not observed. Eleven to twelve inconspicuous tubular precloacal supplements located 15–48 µm apart. Tail conical, with rounded tip, 2.8–3.3 cloacal body diameters long, without somatic setae. Three caudal glands and spinneret present.

Female

Similar to males, but with excretory pore located at or slightly anterior to level of nerve ring. Reproductive system didelphic with two opposed and reflexed ovaries both located ventrally or to the left of intestine; spermatheca absent. Vulva situated at mid-body. Proximal portion of vagina surrounded by constrictor muscle, small vaginal glands present. Uterus wall not cuticularized.

Figures

Fig. 13. Aegialoalaimus magnus sp. nov. A–B, D. Paratype (NIWA154920). C, E–F. Holotype (NIWA 154918). A–B. Female anterior body region. C. Male cephalic region. D. Female posterior body region. E. Male copulatory apparatus. F. Male posterior body region. Scale bar: A–B = 100 µm; C = 60 µm; D–E = 50 µm; F = 125 µm.

Fig. 14. Aegialoalaimus magnus sp. nov.A. Entire male, holotype (NIWA154918).B. Female reproductive system, paratype (NIWA154920). Scale bar: A = 300 µm; B = 175 µm.

Fig. 15. Aegialoalaimus magnus sp. nov. Light micrographs.A–D. Paratype (NIWA154920).E–F. Holotype (NIWA154918). A. Anterior portion of female showing amphid. B. Anterior portion of female showing cephalic sensilla and buccal cavity. C. Anterior portion of female showing buccal cavity. D. Junction of pharynx and intestine. E. Anterior body portion of male. F. Posterior body portion of male. Scale bar: A–D = 20 µm; E = 44 µm; F = 50 µm.