Deontolaimus catalinae, Holovachov, Oleksandr & Boström, Sven, 2015

Holovachov, Oleksandr & Boström, Sven, 2015, Swedish Plectida (Nematoda). Part 10. The genus Deontolaimus de Man, 1880, Zootaxa 4034 (1), pp. 1-44 : 16-19

Deontolaimus catalinae sp. n.

( Figs 7–8 ; Table 4 )

Type material examined. Holotype male (slide # Type-8771), and ten male and eight female paratypes (slides # Type-8771—Type-8775) deposited in the invertebrate type collection of the Department of Zoology, Swedish Museum of Natural History, Stockholm, Sweden.

Type locality. 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.

Description. Adult. Body slender, cylindrical over most of its length, tapering anteriorly in anterior half of pharyngeal region and posteriorly on tail; weakly ventrally curved upon fixation, especially so in posterior part. Cuticle annulated; annules without ornamentation. Lateral field present, single cuticular ridge weakly demarcated by two lines extending from intestinal region to posterior part of tail. Crystalloids absent. Body pores and epidermal glands absent. Somatic sensilla present, equally distributed along entire body; anterior-most somatic sensilla are located short distance posterior to amphid, near onchiostyle base. Labial region truncate conoid, continuous with body contour; lips fused. There is a narrow slit-like structure on the dorsal side from the oral opening, which function and homology is unclear. Annulation along anterior-most part of body very weak; anterior-most annule appearing posterior to amphid and cephalic sensilla bases. Inner labial sensilla small papilliform, distinct, located on the anterior surface of labial region. Outer labial sensilla small pore-like, located on the outer surface of labial region. Cephalic sensilla setiform, equal to 0.2 labial region diameter in length, their bases are located at level with posterior margin of amphid. Subcephalic and cervical sensilla absent. Amphidial aperture circular, fovea ventrally-unispiral, making one turn, located in front of cephalic sensilla bases. Ocelli absent. Nerve ring surrounding pharynx just anterior to its middle. Hemizonid not seen. Secretory-excretory system present; renette cell located on left-hand side of body along anterior part of intestine; it extends anteriorly along ventral side of pharynx, excretory ampulla indistinct. Excretory canal weakly cuticularised, extends from renette cell for a short distance and opens to exterior on ventral side of anterior body end, short distance posterior to onchiostyle base, anterior to anterior-most alveolum in males. Oral opening terminal. Buccal cavity uniformly tubular: cheilostom barrel-shaped; stegostom tubular, with large dorsal onchiostyle. Onchiostyle with bluntly rounded tip and subcylindrical body. Pharynx muscular in its anterior part and glandular in its posterior part, 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 (more curved ventrad in male) elongate-conoid, ventrally curved. Three caudal glands present, their nuclei are incaudal. Spinneret short, thornlike, unsclerotized, 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 anterior half of body, extending from anterior body end to about middle of body, they are very small slit-like. Tubular supplements absent. Midventral precloacal sensilla absent. Two postcloacal sensilla present, located subventrally at level of posterior one-third of tail length; sclerotized lamina absent. Tail with two pairs of papilliform sensilla: first (counting from cloaca) subventral pair located short distance posterior to cloacal opening, second subventral pair located at posterior one third of tail length.

Female. Reproductive system didelphic, amphidelphic; ovary branches reflexed antidromously. Anterior genital branch 128–248 µm long (equal to 8.2–15.3% of total body length), located on right-hand side of intestine (n = 5), posterior genital branch 155–272 µm long (equal to 10.0–16.8% of total body length), located on left-hand side of intestine (n = 5). Oviduct short. Spermathecae filled with sperm. Uterus voluminous. Vagina straight, 0.2– 0.4 times vulval body diameter long. Epiptygmata, pars refringens vaginae and sensitive structures around vulva absent. Rectum 0.9–1.1 anal body diameters long.

Diagnosis. Deontolaimus catalinae sp. n. is characterized by having body 1.3–1.7 mm long; anterior-most somatic sensilla located short distance posterior to amphid; cephalic sensilla equal to 0.2 labial region diameter in length; amphidial fovea ventrally-unispiral with one turn, located in front of cephalic sensilla bases; excretory pore located short distance posterior to onchiostyle base; onchiostyle with bluntly rounded tip and subcylindrical body; male with alveolar supplements extending from anterior end to middle of body, tubular supplements absent; spicules 36–40 µm long; didelphic female reproductive system.

Remarks. Our specimens are similar to Camacolaimus barbatus described by Pastor de Ward (1984) from Argentina in body measurements, shape of anterior body end, shape of spicules, gubernaculum and spinneret, and presence of fine slit-like supplements in male (C. Pastor, in litt. 3 June 2015). It differs in having shorter cephalic setae (1.5 µm in Swedish specimens vs 4 µm in specimens from Argentina) and shorter spicules (36–40 µm in Swedish specimens vs 45–50 µm in specimens from Argentina).

The new species closely resembles Deontolaimus parvus ( Timm, 1961) comb. n. in having the excretory pore located close to anterior body end. No other species of Deontolaimus is known to share this feature with D.

catalinae sp. n. These two species, however, can be easily separated from each other based on the following characters: body size (1.28–1.66 mm in D. catalinae sp. n. vs 0.73–0.75 mm in D. parvus ) and position of excretory pore (9–17 µm from cephalic setae bases in D. catalinae sp. n. vs at level with cephalic sensilla bases in D. parvus ).

Figures

FIGURE 7. Deontolaimus catalinae sp. n. holotype male (D – E, G – H) and paratype female (A – C, F). A: Female reproductive system. B & D: Anterior end, surface view; C & E: Anterior end, median section; F: Female tail; G: Pharyngeal region, median section; H: Male posterior region. Scale bar: A – H = 20 µm.

FIGURE 8. Deontolaimus catalinae sp. n., male (A – E, G – H) and female (F, I). A – B: Anterior end, right ventro-sublateral view (arrow points at excretory pore); C: Anterior end, left lateral view; D: Cloacal opening, subventral view; E: Anterior end, semi en face view; F: Vulva; G: Male tail, right sublateral view; H: Alveolar supplement; I: Female tail, left lateral view. Scale bars: A – F, H = 2 µm, G, I = 10 µm.