Egtitus neocyatholaimus ( Kreis, 1936 ) Thorne, 1967

Andrássy, István, 2012, On the “ Paractinolaimus ” genus group (Nematoda: Actinolaimidae), with description of five new and two rare species of Egtitus Thorne, 1967, Journal of Natural History 46 (7 - 8), pp. 453-494 : 466-469

Egtitus neocyatholaimus ( Kreis, 1936) Thorne, 1967

( Figures 4A–E and 5A, B )

Present female: L = 2.63 mm; a = 51; b = 4.7; c = 11; ć = 8.0; V = 46%. Present males (n = 2): L = 2.38–2.54 mm; a = 46–50; b = 4.0–4.3; c = 86–92; ć = 0.8–0.9. Female after Kreis (1936): L = 2.19 mm; a = 32; b = 4.7; c = 9.4; ć = 8; V = 42%.

General characters of the present specimens

Body in female nearly straight, in male ventrally curved on its posterior end, strongly tapered towards anterior end, 48–55 µm wide at mid-region. Cuticle smooth, 2.5–3.0 µm thick on most of body. Lip region small, 15–16 µm wide, separated by a slight depression. Body at posterior end of pharynx 3.2–3.3 times as wide as lip region. Amphids caliciform with apertures about half as wide as corresponding head diameter.

Labial and dental chambers separated, the former 9–10 µm, the latter 6–7 µm broad. Dental walls weakly ribbed, without denticles. Onchia simple. Odontostyle 22–24 µm long, 1.3–1.5 times longer than labial width and 2 µm thick, thicker than cuticle (1.5 µm) at same level; the aperture occupying one-third of its length. Guiding ring thin, 7 µm wide, 15 µm from anterior body end. Pharynx tripartite, 548–630 µm long, enlarged at 52–54% of its length. Medial part relatively short, 68–75 µm, 12–13% of pharyngeal length. Pharyngeal nuclei obscure. D = 55–57% (12–14% of total body length), AS uncertain, PS 1 = 68–71%, PS 2 = 70–73%. Glandularium 233–280 µm long. Cardia conical. Intestinal lumen roomy.

Female

Amphidelphic with moderately long genital branches; anterior branch 6.4 body diameters long or occupying 13% of body length, posterior branch 7.4 body diameters long or occupying 15% of body length. Vulva longitudinal with sclerotized inner pieces, vagina 26 µm, half as long as corresponding body width. No uterine eggs. Distance between posterior end of pharynx and vulva somewhat longer (1.1 times) than pharynx. Rectum 1.7, pre-rectum 3.0 times the anal body width long. Vulva– anus distance equal to five tail lengths. Tail conoid then filiform, 238 µm long or 9% of entire length of body, hair-like and straight on its tip.

Male

Diorchic with well-developed testes. Spermatozoa fusiform. Spicula 54–58 µm long in curvature, much longer than tail. Ventromedial supplements 12 or 13, small but clearly discernible, at intervals of 9–12 µm, the posteriormost well before the spicula. Pre-rectum beginning within the range of supplements. Tail 26–34 µm long or only 1.0–1.2% of total body length, conoid-rounded.

Remarks

Among the representatives of Egtitus there are five that possess a comparatively long tail, 8 to 11 anal body diameters long, namely E. kazirangus , E. neocyatholaimus , E. neoelaboratus , E. nudus and E. proximus . The tail of the remaining species is shorter, three to six anal body diameters. The present specimens, one female, three female-like juveniles and (with the exception of the sexual characters) also the two males, agree very closely with the original description of E. neocyatholaimus . Kreis (1936) described this species under the name Actinolaimus neocyatholaimus Kreis, 1936 from Madras, India, on the basis of a single female. To date it has not been rediscovered. The similarity between the present female and that of Kreis is easily seen if the morphometric data are compared: the first values refer to the present female, the second (in parentheses) to the female described by Kreis: L = 2.6 (2.2), b = 4.7 (4.7), c = 11.0 (9.4), ć = 8.0 (8.0), V = 46 (42), labial diameter 16 (17) µm, body diameter at pharyngeal terminus / labial diameter 3.3 (3.4), odontostyle length 24 (24) µm, pharynx enlarged at 53 (52)%, tail length 238 (233) µm. Unfortunately, male characters cannot be compared.

If we compare the present species with the four other long-tailed species, we find that it differs from E. kazirangus and E. neoelaboratus by the narrower lip region (15–16 versus 20–22 µm) and the greater number of supplements (12–13 versus 7–8); from E. nudus by the odontostyle longer than lip region width (1.3–1.5 versus 1.0 times), and from E. proximus by the longer body (2.6 versus 1.6–2.0 mm), odontostyle longer than lip region width (versus equally long), and the higher number of supplements (12–13 versus 9–10).

On the basis of these findings we may suppose that the present species is very likely conspecific with E. neocyatholaimus . The only difference seen in the size of the body (2.4–2.6 versus 2.2 mm) can be considered an intraspecific variation.

Habitat and locality

Fallen leaves and detritus from a rain forest, c. 1000 m above sea level, Baiyer River Sanctuary , Western Highlands Province, Papua New Guinea; collected in September 1969 by J. Balogh .

This is the first report of E. neocyatholaimus since its original description.

Figures

Figure 4. Egtitus neocyatholaimus (Kreis, 1936) Thorne, 1967. (A) Anterior end; (B) medial part of pharynx; (C) cardial region; (D) vulval region; (E) female tail. Scale bars 20 µm.

Figure 5. Egtitus neocyatholaimus (Kreis, 1936) Thorne, 1967. (A, B) Posterior end of male. Scale bar 20 µm.