Odilia similis, Smales, 2009

Smales, L. R., 2009, Helminths Of Melomys Rufescens And Melomys Spp. (Muridae: Hydromyinae) From Papua New Guinea With The Descriptions Of A New Genus And Five New Species In The Heligmonellidae (Nematoda: Trichostrongyloidea), Raffles Bulletin of Zoology 57 (1), pp. 5-15 : 11

Odilia similis , new species

( Figs. 29–38 )

Material examined. – Holotype male and allotype female: BBM- NG-53130, from the small intestine of Melomys rufescens ( Muridae : Hydromyinae ), type host, Kalolo, Morobe Province, Papua New Guinea, coll. O. R. & J. W. Wilkes, 28 Aug.1966

Paratypes: 1 male, 2 females, SAM AHC 34782; collecting data as above .

Voucher specimens: 2 males, 3 females, BBM-NG-54020 & 20 males, 18 females, BBM-NG- 53691, from the small intestine of Melomys rufescens , 10 km west of Bulolo , 7°12'S 146°39'E, Morobe Province, coll. A. C. Zeigler, 7 Aug.1967 ; 3 males, 2 females, AM W31470, from the small intestine of Melomys rufescens, Munimun Village, Aguan , 9°53'S 149°23'E Sanduan Province, coll. P. German, 8 Aug.1992 .

Prevalence. – Four of 25 M. rufescens and one of 10 Melomys spp.

Etymology. – The species name indicates that whilst having a unique set of characters there are no singular morphological features to highlight.

Description. – Small coiled worms; prominent cephalic vesicle present; buccal capsule vestigial. Mouth opening triangular with rudimentary lips; labial and cephalic papillae not observed. Oesophagus claviform. Nerve ring surrounds oesophagus in middle third, deirids and excretory pore at about same level, posterior to nerve ring. Synlophe of longitudinal cuticular ridges extends from the posterior margin of the cephalic vesicle to just anterior to the bursa or vulva; 35–37 ridges in anterior, 35 in midbody of male. Axis of orientation from ventral right to dorsal left sides, inclined about 60° from sagittal axis. Ridges 1–16 increasing slightly in size; ridges 1’–10’ increasing in size, ridges 11’–21’ smaller. Posterior region of body with 28–30 ridges reduced in size; 20 ridges dorsal side, 8–10 ridges ventral side.

Male (holotype and 9 paratypes): Length 2.1–3.2 (2.5) mm, maximum width 67–100 (84). Cephalic vesicle 39.5–49.5 (43) long, 23–29.5 (27) wide. Oesophagus 320–520 (390) long; nerve ring 130, excretory pore 180, deirids 180 from cephalic end. Bursa slightly asymmetrical, right lobe larger, rays of right lobe more robust; without dorsal median dorsal notch. Dorsal ray symmetrical, divided at about half its length, each branch dividing again at distal tip; terminal divisions, rays 9, 10 symmetrical; rays 8 arising at same level proximally to division of dorsal ray, right ray 8 slightly more robust than left. Rays 4, 5, 6 with common stem, reaching margin of bursa, rays 6 curving anteriorly, rays 4, 5 curving posteriorly. Rays 2, 3 with common stem, diverging distally, curving posteriorly, reaching margins of bursa. Genital cone short, lightly sclerotized, with papillae 0 and 7. Spicules equal, filiform, tips simple, sharply curved, 340-450 (390) long. Gubernaculum 37–41 (39) long.

Female (allotype and 9 paratypes): Length 2.4–3.4 (2.8) mm, maximum width 66–87 (81). Cephalic vesicle 36–52 (43) long, 23–33 (28) wide. Oesophagus 250–520 (370) long; nerve ring 200, excretory pore 250, deirids 250 from cephalic end. Vulva opens 66–72.5 (71) from tail tip. Monodelphic; ovejector with sphincter 40, 40, and vestibule 40, 50, about same length, infundibulum 30, 40, and vagina, 25, 30, shorter. Tail blunt, conical, tip rounded, 16.5–24 (19) long. Eggs thin- shelled, ellipsoidal, in utero 53–63 (57) by 32–33 (32.8).

Remarks. – Although the fixation of this material, in situ in the intestine of the host, was not ideal it was sufficient to allow adequate examination of the specimens. Odilia similis , new species, has every morphological character of the genus Odilia ( Mawson, 1961) (see Durette-Desset, 1983). Following the key to the species of Odilia of Smales (2005b), O. similis , new species, with 35 ridges in the midbody of the male, falls between the group of species with up to 35 ridges, O. maxomyos Hasegawa et al. 1999 , and O. praeputialis Gibbons & Spratt, 1995 , and the group with more than 35 ridges in the midbody, O. polyrhabdote ( Mawson, 1961) and O. uromyos ( Mawson, 1961) . Odilia similis , new species, further differs from each of these species in having a spicule to body length ratio of 1: 6.5, simple pointed spicule tips and a female tail blunt, conical, neither twisted nor with a praepuce ( Smales, 2005b).

Figures

Figs. 29–38. Odilia similis, new species, from Melomys rufescens and Melomys spp. from Papau New Guinea: 29, female anterior end, lateral view; 30, male cross section, anterior body; 31, bursa, right lateral view; 32, male cross section, midbody; 33, spicule tips; 34, dorsal ray; 35, female posterior end, lateral view; 36, male cross section, posterior body; 37, gubernaculum, lateral view; 38, genital cone, lateral view. Figs. 39–43. Odilia species from Melomys rufescens and Melomys sp. from Papau New Guinea: 39, male cross section, anterior body; 40, dorsal ray; 41, bursa, left lateral view; 42, male cross section, midbody; 43, spicule tips. Scale bars: 29 = 100 μm; 30–34, 37–43 = 25 μm; 35 = 200 μm; 36 = 10 μm.