Stegelleta tuarua Yeates, 1967

Boström, Sven & Holovachov, Oleksandr, 2014, Descriptions of species of Stegelleta Thorne, 1938 (Nematoda, Rhabditida, Cephalobidae) from California, New Zealand and Senegal, and a revision of the genus, European Journal of Taxonomy 87, pp. 1-19 : 16-17

Stegelleta tuarua Yeates, 1967

Fig. 4E–G , Table 2

Stegelleta tuarua Yeates, 1967: 536–538 , fig. 5.

Diagnosis

Stegelleta tuarua is characterised by a 635 µm long body in females and 563–739 µm in males; cuticle divided by regular longitudinal striations into 40–44 rows of blocks at midbody; lateral field with five incisures extending almost to tail terminus in females and in males; three pairs of asymmetrical lips, pairs of lips separated by U-shaped primary axils without guarding processes, secondary axils demarcated by a shallow incisure, each lip asymmetrically rectangular with a smooth margin and one tine; three labial probolae, bifurcated at about 1/5 of their length; pharyngeal corpus 4.2–5.4 times isthmus length; nerve ring and excretory pore at level of isthmus and deirids at level of bulb; vulva and spermatheca undescribed, postuterine sac about 1 vulval body diameter long; spicules 21–25 µm long.

Material examined

NEW ZEALAND: 2 ♂♂, SMNH 135945–135946, 18 May 2008, North Island, Wanganui, Castlecliff beach, partly stabilized coastal sand dunes with Ammophila arenaria , 50 cm deep, legit G. Yeates.

Description

Adult

Body slightly arcuate ventrad when killed by heat. Cuticle annulated, annuli 2.4 µm wide at midbody and 3.0– 3.4 µm wide in pharyngeal region. Cuticle tessellated: longitudinal striae giving it a tiled appearance, tiles are not equal in size and are not arranged in straight rows, approximately 40–44 rows of blocks at midbody. Lateral field with five incisures occupying about 20% of body diameter, extending almost to tail terminus in females. Lip region slightly offset, carrying 6 + 4 papillae and two round amphids. Three pairs of asymmetrical lips, one dorsal and two ventrolateral. Pairs of lips separated by U-shaped primary axils without guarding processes. Each pair with a shallow incisure demarcating a secondary axil. Each lip asymmetrically rectangular with a smooth margin and one acute tine extending along the primary axil. Three labial probolae, 7.0– 8.5 µm high, bifurcated at about 1/5 of their length. Stoma somewhat longer than lip region diameter. Stomatal parts not clearly discernible. Cheilorhabdia bacilliform in lateromedian view; metastegostom with a dorsal denticle. Pharynx cephaloboid. Pharyngeal corpus cylindrical; isthmus narrow, not clearly demarcated from corpus; bulb oval, with valves. Nerve ring and excretory pore at level of isthmus and deirids at level of bulb.

Male

Reproductive system monorchic, dextral in position; testis reflexed ventrad anteriorly. Spicules paired and symmetrical, curved ventrad; with oval manubrium and subcylindrical, gradually narrowing shaft. Gubernaculum wedge-shaped, cornua crurum present. Tail strongly arcuate ventrad, conoid with rounded terminus. The two outer lateral lines extend posterior to the subdorsal papilla close to tail terminus, transforming into a cuticular ridge that reaches tail terminus. Genital papillae arranged as follows: two pairs subventral precloacal (at 36 µm and at 74 µm anterior to cloaca), one pair subventral adcloacal, a single midventral papilla on anterior cloacal lip; two pairs (one ventrosublateral and one lateral) at midtail; three pairs (one lateral, one subventral and one dorsosublateral) closer to tail terminus. Phasmids located at about two-fifths to half of tail length.

Female

Not found in our study.

Remarks

The specimens described here agree well in main morphological and morphometric features with the original description by Yeates (1967) of the males of S. tuarua from New Zealand.

Figures

Fig. 4. A–D. Stegelleta ophioglossa Andrássy, 1967. A. Pharyngeal region. B. Anterior end, surface view. C. Female gonad. D. Female tail. E–G. Stegelleta tuarua Yeates, 1967. E. Pharyngeal region. F. Anterior end, surface view. G. Male tail. Scale bar = 20 µm.