Neodiplopeltula bathmanni ( Jensen, 1991 ) Holovachov & Boström, 2018

Holovachov, Oleksandr & Boström, Sven, 2018, Neodiplopeltula gen. nov. from the west coast of Sweden and reappraisal of the genus Diplopeltula Gerlach, 1950 (Nematoda, Diplopeltidae), European Journal of Taxonomy 458, pp. 1-34 : 24-29

Neodiplopeltula bathmanni ( Jensen, 1991) gen. et comb. nov.

Figs 11–13 ; Table 5

Diagnosis (based on combined data)

Neodiplopeltula bathmanni gen. et comb. nov. is characterised by a 0.85–2.08 mm long body; refractive plates underlying cephalic cuticle around amphids present, not joined, 19–29 µm long and 12–16.5 µm wide; cephalic sensilla 2–3.5 µm long; amphidial fovea 20–32 µm long and 4–7 µm wide; oral opening 6–16 µm from anterior end, at level with or posterior to cephalic setae bases; secretory-excretory pore located opposite to posterior part of pharynx; tail 1.5–2.2 anal body diameters long; vagina with epiptygmata; spicules 52–66 µm long.

Material examined

SWEDEN: 1 ♀, 4 ♂♂, Skagerrak, 58°19′15.6″–20.9″ N, 10°29′33.5″–34.0″ E, soft bottom at a deep of 352–374 m, 10 Sep. 2012, “Inventering Bratten” leg. (SMNH-169274 and SMNH-169284); 1 ♀, Skagerrak, 58°22′17.8″–19.4″ N, 10°23′50.8″–24′03.2″ E, soft bottom at a deep of 351–387 m, 10 Sep. 2012, “Inventering Bratten” leg. (SMNH-169275); 1 ♀, 1 ♂, Skagerrak, 58°34′21.3″–16.6″ N, 10°38′11.2″–29.4″ E, soft bottom at a deep of 139–153 m, 12 Sep. 2012, “Inventering Bratten” leg. (SMNH-169277).

Description

Adult

Body cylindrical, posteriorly tapering in tail region, straight or weakly ventrally curved upon fixation. Cuticle finely transversely striated along entire body, except for visually smooth labial region and terminal part of tail (striation can be observed under LM but very fine and shallow and cannot be measured with confidence); longitudinal striation not observed. Somatic sensilla visible along pharyngeal region (cervical setae, see below) and on tail. Labial region bluntly rounded, lips fused. Refractive plates underlying cephalic cuticle around amphids present (periamphideal), extending from level of anteriormost edge of amphid posteriorly some distance behind the posteriormost edge of amphid; refractive plates are elongated ovoid in shape (plate edges not incised), not connected with each other on ventral and on dorsal sides. Inner labial sensilla indistinct. Outer labial sensilla papilliform, located on anterior surface of lips. Cephalic sensilla setiform, bases of dorsosublateral setae located at level with or anterior to oral opening. Cervical sensilla absent; small papilliform somatic sensilla visible posterior to amphid and refractive plate. Amphids similar in shape and size between sexes: amphidial fovea inverted U-shape branches unequal in length with either dorsal or ventral branch 1.0–2.0 µm longer than opposite branch. Oral opening shifted towards dorsal side of body. Stoma subcylindrical: cheilostom broad; gymnostom barrel-shaped, with weakly cuticularised walls; stegostom short conoid, its lining uniform with lining of pharynx. Pharyngeal tubes absent. Pharynx subcylindrical, muscular, with evenly distributed myofilaments, gradually expanding towards posterior end; not subdivided in distinct sections; pharyngeal lumen uniform in thickness along entire pharynx length; valves absent. Secretory-excretory system present; secretory-excretory pore located along ventral body line opposite to 4/5 th of pharynx; secretory-excretory duct very short, leading from pore to ampulla; renette cell small, its body adjacent and ventral to posterior part of pharynx. Tail conoid with bluntly rounded terminus. Caudal glands opening via three separate subterminal openings, spinneret absent.

Female

Reproductive system didelphic, amphidelphic, ovary branches outstretched and symmetrical, on opposite sides of intestine. Anterior genital tube 97–242 µm long, situated to either right (n = 2) or left (n = 1) of intestine; posterior genital tube 103–245 µm long situated to either left (n = 2) or right (n = 1) of intestine. Vulva transverse slit, located posterior to midbody. Vagina straight, with developed sphincter muscle surrounding proximal part and distinct epiptygmata in distal part; pars refringens vaginae absent. Sacklike spermatheca present, filled with oval spermatozoa in fertilized specimens. Rectum short.

Male

Reproductive system diorchic, testes opposed; anterior testis outstretched and posterior testis reflexed (cannot be measured). Spicules paired and symmetrical, strongly curved, with ovoid manubrium and fusiform shaft. Gubernaculum plate-like, with pair of strong closely set caudal apophyses variable in shape ( Fig. 13 C–E). Caudal setae present, several ventrosublateral pairs arranged in rows along entire tail length, one dorsosublateral pair located close to tail terminus (not always visible).

Remarks

No morphological or morphometric differences can be found between the recent specimens and the original description of this species ( Jensen 1991).

Figures

Fig. 11. Neodiplopeltula bathmanni (Jensen, 1991) gen. et comb. nov. (♂ SMNH-169274 and ♀ SMNH-169277). A. Female anterior end, surface view. B. Female pharyngeal region, optical median section. C. Male tail. D. Male anterior end, surface view. E. Anterior part of female reproductive system. F. Female tail. Scale bar = 20 µm.

Fig. 12. Neodiplopeltula bathmanni (Jensen, 1991) gen. et comb. nov. (♂ SMNH-169274 and ♀ SMNH- 169277). A. ♂, entire specimen. B. ♀, entire specimen. C. Anterior testis. D. Posterior testis. Scale bars: A–B = 100 µm: C–D = 50 µm.

Fig. 13. Neodiplopeltula bathmanni (Jensen, 1991) gen. et comb. nov. (SMNH-169274 and SMNH- 169277). A. Male anterior end, lateral view. B. Female anterior end, lateral view. C–E. Variability in the shape of gubernaculum apophyses in different specimens (arrows). Scale bars = 10 µm.