Paradicelis bursata, Ivanova, Elena S. & Hope, Duane, 2009

Ivanova, Elena S. & Hope, Duane, 2009, A new genus and three new species of Drilonematidae (Rhabditida, Drilonematoidea) from earthworms, Zootaxa 2293, pp. 53-67 : 58-59

Paradicelis bursata gen. n., sp. n.

( Fig 3 )

Measurements: Holotype male: L = 6920 µm; D = 170 µm; anal diameter = 80 µm; Ph = 230 µm; nerve ring = 350 µm; excretory pore = 307 µm; tail = 220 µm; Sp (arc) = 136 µm; Sp (chord) = 118 µm; Gub = 65 µm; a = 40.7; b = 30.1; c = 31.5.

Paratype male (fragment, anterior end): Ph = 212 µm; nerve ring = 347 µm; excretory pore = 267 µm.

Male: Body long, cylindrical, barely tapering toward anterior end, with short conical tail. Cuticle finely striated. Lateral chords faint, about 5 µm wide at anterior, 20 µm wide at mid-body. Head bluntly rounded, bearing four papilliform cephalic sensilla. Mouth aperture terminal. Stoma short, infundibular, about 4–5 µm long and 6–7 µm in diameter. Amphids pore-like but bundle of amphidial sensilla prominent. Pharynx cylindroid, musculature well-developed, anterior diameter about 26–28 µm, expanded near base to 40–41 µm. Three large nuclei of pharyngeal glands at basal portion of pharynx. Nerve ring surrounding constriction of intestine about two pharynx lengths from anterior body end. Excretory pore 3 µm in diameter, situated anterior to nerve ring. Excretory duct 35–45 µm long, 1 µm in diameter, with expanded walls; excretory cell large. Cardia comprised of two cells, 12–15 µm long. Intestine well-developed, thick-walled. Testis very long, reflexed about two pharyngeal lengths from anterior body end (505–512 µm); distal flexure 303–320 µm long; testis looped between flexure and vas deferens. Va s de f eren s long, with thick glandular cells. Ejaculatory duct thin, muscular. Spermatids in ejaculatory duct spherical, about 7–9 µm in diameter. Tail coiled ventrally, conical with blunt tip, bearing small symmetrically situated caudal fimbriate organs slightly posterior from mid-tail. Irregular bursa present from before cloacal aperture to near tip of tail. Four pairs of long, whip-like caudal sensilla, subventral, extending to edge of bursa; three equally-spaced precloacal pairs and another pair mid-way between anus and caudal organ. Two equal spicules, each curved with proximal half expanded to 17 µm and with short rounded capitulum 17 µm long and 12 µm in diameter; each capitulum with proximally deflected fringe. Distal half of each spicule nearly cylindrical, 5 µm in diameter, with rounded tip. Gubernaculum about half spicule length, thick, 11 µm in diameter, heavily sclerotized, with distal spade-like process 5 µm long. Caudal organs 150 µm posterior from cloacal aperture, circular, slightly raised, with aperture 5 µm in diameter, with convex radially striated rim 11 µm in diameter. Copulatory muscles prominent.

Female: Not found.

Type material: Holotype male USNM 1117739 deposited in the Smithsonian Institution’s National Museum of Natural History. Fragment of male (anterior end) is in the first author’s collection.

Type host and locality: Coelomic cavity of Pheretima longicauliculata Gates 1931 USNM 27569, collected in Doi Sutep, Thailand, September 1936, leg. Gates.

Etymology: The specific epithet is derived from the Latin word bursa, a feature present in the new species.

Diagnosis and relationships. Paradicelis gen. n. is characterized within Dicelinae by having a cylindroid pharynx slightly expanded near the base, nerve ring situated around the intestine, excretory pore situated in front of the nerve ring, irregular bursa, whip-like copulatory sensilla, and small fimbriate organs near mid-tail. Paradicelis gen. n. seems closely related to Dicelis and Adieronema . It resembles these genera in having similar general body proportions, pore-like amphids, muscular cylindroid pharynx, nerve ring situated around intestine, and similarly-shaped caudal organs. Whereas bursa and whip-like copulatory sensilla have not been encountered within either genus, these features are characteristic for several species in another subfamily of Drilonematidae , the Iponematinae ( Iponema laotense Spiridonov , Filiponema philippinense Timm & Maggenti, F. b u r m e n s e Timm, F. sarmathicus Spiridonov et al. , Plutellonema clitellatum Timm & Maggenti , Tonoscolecinema setosum Timm ). In these species, however, these features are always accompanied by large circular or elliptical amphids, clavate pharynx and the nerve ring situated around the pharyngeal isthmus ( Timm & Maggenti 1966; Timm 1967; Spiridonov et al. 1989; Spiridonov 1994a). The structure of the bursa is similar in all drilonematids, including members of the other family, Homungellidae ( Timm 1966a; Spiridonov 1994b).

From Dicelis , the new genus can also be distinguished by the excretory pore being situated in front of the nerve ring (as opposed to behind it for all other Dicelis species known, and this position remains unchanged in juveniles and adults). Although no females were found, the character of having bursa supported by whip-like sensilla is specific at the generic level in Drilonematidae .

Figures

FIGURE 3. Paradicelis bursata gen. n., sp. n. male. A: entire view; B: head; C: pharyngeal region; D: excretory pore; E: posterior region of body; F: tail; G: spicule and gubernaculum. All in lateral position. (Scale bars in µm.)