Deontolaimus longicauda

Holovachov, Oleksandr & Boström, Sven, 2015, Swedish Plectida (Nematoda). Part 10. The genus Deontolaimus de Man, 1880, Zootaxa 4034 (1), pp. 1-44 : 13-15

Deontolaimus longicauda (de Man, 1922) comb. n.

( Fig. 6 ; Table 3 )

Material examined. One male and three females (slides # 145496–145497) deposited in the general invertebrate collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Habitat and locality. Sand and shells from 15–22 m deep, Bonden island in Skagerrak off the west coast of Sweden (N 58 12' 37'', E 11 18' 53''), 0 9 August 2011, legit O. Holovachov (one male and three females).

Description. Adult. Body slender, cylindrical over most of its length, tapering anteriorly in anterior half of pharyngeal region and posteriorly on tail; strongly ventrally curved upon fixation, especially so in posterior part. Cuticle annulated; annules without ornamentation. Lateral field present, single cuticular ridge demarcated by two lines extending from anterior part of intestine to posterior part of intestine. Crystalloids absent. Body pores and epidermal glands absent. Somatic sensilla present, equally distributed along entire body; anterior-most somatic sensilla are located 1–11 annules posterior to amphid. Labial region rounded, continuous with body contour; lips fused. Annulation along anterior-most part of body very weak; anterior-most annule appearing posterior to amphid and cephalic sensilla bases. One circle of labial sensilla visible on the anterior surface of labial region, they are small papilliform. Cephalic sensilla setiform, equal to 0.5–0.6 labial region diameter in length, their bases are located short distance posterior to amphid. Subcephalic and cervical sensilla absent. Amphidial fovea ventrallyunispiral, making one turn, located anterior to cephalic sensilla bases. Ocelli absent. Nerve ring surrounding pharynx anterior to its middle. Hemizonid not seen. Secretory-excretory system present; renette cell located on lefthand side of body along anterior part of intestine; it extends anteriorly along ventral side of pharynx and forms excretory ampulla just posterior to nerve ring level. Excretory canal weakly cuticularised, extends from excretory ampulla for a short distance and opens to exterior on ventral side, just posterior to nerve ring. Oral opening terminal. Buccal cavity uniformly tubular: cheilostom barrel-shaped; stegostom tubular, with large dorsal onchiostyle. Onchiostyle with bluntly rounded and strongly sclerotized tip and subcylindrical body. Pharynx muscular in its anterior part and partly glandular in its posterior part, more so in its dorsal sector, cylindrical anteriorly, expanding posteriorly; not subdivided into sections; without bulbs; valvular apparatus absent. Dorsal pharyngeal gland orifice opens at base of onchiostyle; orifices of subventral pharyngeal glands indistinct. Cardia short, embedded in intestine. Tail similar in shape in both sexes (shorter and more curved ventrad in male) elongate-conoid to subcylindrical, ventrally curved. Three caudal glands present, their nuclei are incaudal. Spinneret large conoid, functional.

Male. Reproductive system diorchic, both testes outstretched. Spicules paired, symmetrical, with arcuate subcylindrical shaft and small manubrium; manubrium is ventrally inclined. Gubernaculum present, plate-like, with paired dorsal apophysis. Alveolar supplements present along most of the body, extending from anterior body end to posterior part of intestine, ending several body diameters anterior to cloaca, they are very small and located at the bottom of a narrow ventral groove, difficult to count. Tubular supplements absent. Midventral precloacal sensilla absent. Two postcloacal sensilla present, located subventrally at level of posterior third of tail; sclerotized lamina absent. Tail with three pairs of papilliform sensilla: first (counting from cloaca) subventral pair located less than one body diameter posterior to cloacal opening, second subventral pair located at posterior two-thirds of tail length, and third sublateral pair located at posterior one-fifth of tail length.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 93–103 µm long (equal to 7.0–7.9% of total body length), located on right-hand side of intestine (n = 3), posterior genital branch 65–128 µm long (equal to 5.5–8.6% of total body length), located on left-hand side of intestine (n = 3). Oviduct short. Spermathecae filled with sperm. Uterus voluminous. Vagina straight, 0.3–0.4 times vulval body diameter long. Epiptygmata, pars refringens vaginae and sensitive structures around vulva absent. Rectum 1.0–1.1 anal body diameters long.

Diagnosis. Deontolaimus longicauda is characterized by having body 1.0– 1.5 mm long; anterior-most somatic sensilla located short distance posterior to amphid; cephalic sensilla equal to 0.5–0.6 labial region diameter in length; amphidial fovea ventrally-unispiral with one turn, located short distance anterior to cephalic sensilla bases; excretory pore located just posterior to nerve ring level; onchiostyle with bluntly rounded and strongly sclerotized tip and subcylindrical body; male with alveolar supplements extending from anterior end to several body diameters anterior to cloaca, tubular supplements absent; spicules 30 µm long; didelphic female reproductive system.

Remarks. Recent specimens agree well with the original description (de Man 1922) and subsequent redescriptions ( De Coninck & Schuurmans Stekhoven 1933; Platt & Warwick 1988) in general body measurements, shape, size and location of amphid, length of cephalic setae, and shape of onchiostyle. The only difference is the shorter tail in our male, however, the specimen is not flat on the slide and cannot be measured with full confidence.

V(%) or T(%)?? 49.3? 48–51? 48.4–50.1 Body diameter? 14 19 15–22 21 24–30 Pharynx length? 273 237?? 189 194–242 Tail length? 80 90?? 64 74–111 Anal or cloacal body diam.? 16 15?? 17 16–18

Figures

FIGURE 6. Deontolaimus longicauda (de Man, 1922) comb. n. male (C – D, G – H) and female (A – B, E – F). A & C: Anterior end, surface view; B & D: Anterior end, median section; E: Female reproductive system; F: Female tail; G: Male posterior region; H: Pharyngeal region, median section. Scale bar: A – H = 20 µm.

Tables

TABLE 3. Morphometrics of Deontolaimus longicauda (de Man, 1922) comb. n. based on literature data and specimens from the Swedish coast (all measurements are in µm, except for the ratios a, b, c, c', V, T, NR, EP).

	de Man, 1922	De Coninck & Sch. Stekhoven, 1933	Platt & Warwick, 1988	Recent specimens
Body length a	1 ♀ 1116 52	1 ♂ 1 ♀ 1400 1430 87.4 72.7	?♂♂?♀♀ 1200–1500 64–79	1 ♂ 3 ♀♀ 1059 1183–1483 51.1 46.0–54.5
b c c'	6.2 11.6 6	6.8 6 17.9 17.7 5 6	???? 6 7	5.6 5.5–6.4 16.5 11.9–16.0 3.8 4.6–6.5