Rhadinema timmi Vitiello 1971, comb. n.
Creators: name: Holovachov, Oleksandr
name: Boström, Sven
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Nematoda
Adenophorea
Araeolaimida
Leptolaimidae
Rhadinema
Rhadinema timmi

description: Rhadinema timmi (Vitiello, 1971) comb. n.
(Figs 1–3, 4 A–E, 5 A & C; Tables 1 & 2)
Material examined. 31 males and 25 females (slides # 128858-128862, 133259-133266) deposited in the general invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.
Habitat and locality. Mud from 30–39 m deep, Gullmarn Fjord near Fiskebäckskil, Sweden (N 58° 15' 13'', E 11° 27' 31''), 21 August 2010, legit M. Clément (eight males and four females); muddy sediment from 53 m deep, Skagerrak, off the coast of Sweden (N 58° 20' 06'', E 11° 09' 24''), 0 9 August 2011, legit O. Holovachov (one female); muddy sand 8–15 m deep, Gullmarn Fjord near Fiskebäckskil, Sweden (N 58° 15' 09'', E 11° 27' 54''), 11 August 2011, legit O. Holovachov (11 males and 14 females); soft mud from 44 m deep, Gullmarn Fjord near Fiskebäckskil, Sweden (N 58° 15' 37'', E 11° 27' 43''), 11 August 2011, legit O. Holovachov (one male); soft bottom 352–374 m deep, Skagerrak, Sweden (N 58° 19' 15.6'' –20.9'', E 10° 29' 33.5'' –34.0''), 10 September 2012, legit "Inventering Bratten" expedition (4 females and 2 males); soft bottom 221–260 m deep, Skagerrak, Sweden (N 58° 28' 28.0'' –31.1'', E 10° 33' 19.1'' –23.80''), 11 September 2012, legit "Inventering Bratten" expedition (2 females and 4 males); soft bottom 232–240 m deep, Skagerrak, Sweden (N 58° 27' 36.7'' –43.3'', E 10° 32' 52.0'' –59.4''), 12 September 2012, legit "Inventering Bratten" expedition (5 males).
Description. Adult. Body cylindrical over most of its length, tapering anteriorly in pharyngeal region and posteriorly on tail; straight or curved ventrad upon fixation, more strongly curved ventrad in posterior part in males. Maximum body diameter at vulva in female; male body more cylindrical, with cloacal body diameter the same or somewhat bigger than the diameter at midbody. Cuticle thin and weakly annulated; annuli poorly discernible under the light microscope, without ornamentation. Lateral field absent. Prominent body pores present, arranged in sublateral rows in close pairs on each body side; usually 6–7 body pores are present along each side of pharyngeal region; several body pores scattered over rest of the body. Anteriormost body pore located at level of stoma, just posterior to amphid. Labial region rounded, continuous with body contour, lips fused. Inner labial sensilla indistinct. Outer labial sensilla indistinct under the light microscope, small pore-like as seen under SEM; located on the anterior surface of lips. Cephalic sensilla setiform, equal to 0.3–0.6 of labial region diameter. Subcephalic and cervical sensilla, and ocelli absent. Amphidial fovea round, located at level of middle of stoma. One male specimen with two amphidial foveae on one body side (Fig. 4 D) and normal structure on the other side (Fig. 4 C). Nerve ring surrounding pharynx at level of anterior part of isthmus. Hemizonid not seen. Secretoryexcretory system present, excretory pore located just posterior to nerve ring, renette cell obscure. Buccal cavity uniformly tubular: cheilostom short, with six weakly cuticularised longitudinal rugae; gymnostom short, sclerotized, with bar-shaped rhabdia; stegostom long, tubular, with uniformly thickened lumen. Pharynx muscular, cylindrical anteriorly, with weak basal expansion; basal bulb and valvular apparatus absent. Anterior cylindrical part of pharynx subdivided by breaks in muscular pharyngeal tissue into cylindrical procorpus, cylindrical metacorpus and narrow isthmus. Pharyngeal glands and their orifices indistinct. Cardia short, cylindrical, its posterior part embedded in intestine. Tail almost similar in shape in both sexes (shorter and more curved ventrad in male), elongate-conoid, with subcylindrical distal portion. Three caudal glands present, their nuclei are incaudal. Spinneret functional.
Male. Reproductive system diorchic; both testes outstretched. Spicules paired, symmetrical, with arcuate cylindrical calamus and ovoid manubrium; velum present, broad. Gubernaculum plate-like, with long caudal apophysis and short caudal projection located closer to the ventral body side. Accessory apparatus composed of one midventral precloacal papilliform sensillum located anterior to cloaca, at mid-distance between cloaca and posteriormost tubular supplement; 10–11 evenly spaced midventral tubular supplements extending for 300–353 µm from cloaca towards anterior end; alveolar supplements absent. Tubular supplements straight, complex in shape, with blunt tips. Posteriormost tubular supplement 42–45 µm anterior to cloaca, anterior to spicules. Precloacal subventral sensilla absent. Caudal setiform sensilla present, 6–8 pairs arranged as follows: 3–5 subventral pairs along the anterior to middle part of tail, one subdorsal, one subventral and another one subdorsal pair towards tail tip. One pair of subventral papilliform sensilla located at about anterior one-third of tail, posterior to the first or second (anteriormost) pair of caudal setiform sensilla.
Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 197–307 µm long (equal to 12.1–18.2% of total body length), located on right-hand side of intestine (n=6), posterior genital branch 183–335 µm long (equal to 11.5–20.2% of total body length), located on left-hand side of intestine (n=6). Oviduct a narrow tube. Spermathecae as separate structures indistinct. Uterus a wide and long tube. Vagina straight, 0.3–0.5 times vulval body diameters long; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae absent. Vulva midventral, a transverse slit with small wrinkled lips as seen under SEM. Epiptygmata absent. Two small subventral sensillae are seen under SEM, one on each side of the vulva (Fig. 2 F), however, they are indistinct under the light microscope. Rectum 1.1–1.5 anal body diameters long; surrounded by gland-like cells at intestine-rectum junction.
Diagnosis (supplemented with literature data). Rhadinema timmi is particularly characterised by the 1.3–1.8 mm long body; rounded labial region weakly offset from body contour; cephalic setae 2–4 µm long; amphid located 12–19 µm from anterior end; first body pore located 22–30 µm from anterior end; lateral field absent; stoma tubular: cheilostom with six weakly cuticularised longitudinal rugae, gymnostom with sclerotized barshaped rhabdia, stegostom long, tubular; female without supplements, vagina without pars refringens, vulva midventral; male with 10–11 tubular and without alveolar supplements; spicules arcuate and 21–30 µm long.
Remarks. Current specimens agree well with the type specimens of R. timmi in general morphology, body size, measurements, shape of anterior end and amphids, number and shape of supplements, shape of spicules and gubernaculum. The only differences are a slightly longer and plumper body in females (L= 1534–1759 µm vs. L= 1438–1595 µm in type specimens; a=55.1–70.4 vs. a= 71.9–88.6 in type specimens), somewhat longer tail in both males (135–148 µm vs. 120–130 µm in type specimens) and females (149–162 µm vs. 145–151 µm in type specimens), somewhat longer stoma (31–36 µm vs. 27 µm in type specimens) and slightly longer spicules (23.5– 30.0 µm vs. 21.0–23.0 µm long in type specimens). Vitiello (1971) did not describe longitudinal rugae in the cheilostom in his specimens, but they are rather obvious in his drawings (Vitiello, 1971: Fig. 5 a–b). Unfortunately, the original description of this species is not complete enough to allow any further comparisons.
Systematic position. This species fits within the diagnosis of the genus Rhadinema and of the family Rhadinematidae Lorenzen, 1981 but does not fit within the diagnosis of the genus Leptolaimus de Man, 1876 and of the family Leptolaimidae Örley, 1880 based on the following features: cheilostom with six longitudinal rugae (vs. without rugae in Leptolaimus), lateral field absent (vs. present in Leptolaimus), precloacal sensilla located middistance between the posteriormost supplement and cloacal opening (vs. on the anterior cloacal lip in Leptolaimus); precloacal subventral setiform sensilla absent (vs. present in Leptolaimus).
R. timmi can be easily distinguished from the type and only other known species of the genus Rhadinema, R. flexile (Figs 4 F–H, 5 B & D) in a number of morphological and morphometric characters (Cobb, 1920; Lorenzen, 1972; Holovachov & Boström, 2004; Holovachov, 2006): narrower labial region (5.0–8.0 µm vs. 10.0–13.0 µm in R. flexile), smaller stoma (vs. stoma bigger and more spacious in R. flexile, see Fig. 4 F), absence of sublateral sensilla around the vulval region in females (vs. present in R. flexile, see Fig. 4 H), more anterior position of vulva (V=47–50% vs. V=59% in R. flexile), less arcuate spicules, different shape of gubernaculum (caudal apophyses cup-shaped in R. flexile), and longer tail (c'=6.9–10.8 vs. c'= 5.1–7.2 in R. flexile).
description: Published as part of Holovachov, Oleksandr & Boström, Sven, 2014, Swedish Plectida (Nematoda). Part 5. Rhadinema timmi (Vitiello, 1971) comb. n., pp. 477-486 in Zootaxa 3779 (4) on pages 478-483, DOI: 10.11646/zootaxa.3779.4.6, http://zenodo.org/record/230518