Pogonomicola rugala, Smales, L. R., 2013

Smales, L. R., 2013, Nematodes from the caecum and colon of Pogonomys (Muridae: Anisomyini) from Papua New Guinea with the descriptions of a new genus of Oxyuridae (Nematoda: Oxyurida) and a new species of Trichuridae (Nematoda: Enoplida), Zootaxa 3599 (6), pp. 577-587 : 580-582

Pogonomicola rugala sp. nov.

( Figs 1–10 )

Type host. Pogonomys loriae Thomas.

Site in host. Caecum, colon.

Material examined. Holotype male, allotype female from Pogonomys loriae Doma Peaks, 2400 m elevation, Southern Highlands Province, Papua New Guinea, coll A.B. Mirza and Bin Yuo 13. iv. 1978, BBM NG 105735C; paratypes 10 mature females, 2 juvenile females, same data, BBM NG 105735C.

Other material examined. I female from P. l o r i a e, Munimum Village (9° 53´S 149° 23´E), Milne Bay Province AM W. 42813; 3 females from P. sylvestris Mount Kaindi , Morobe Province BBM NG 51131A, NG 53491C.

Etymology. The species name refers to the folded form of the cervical alae.

Description. General: Small nematodes, typical oxyurid shape, cuticle with transverse striations. Cephalic plate oval, cephalic papillae and amphids at edge of cephalic plate. Mouth opening surrounded by 3 lips without visible posterior edge. Oesophagus with distinct isthmus and terminal bulb. Nerve ring surrounding anterior oesophagus, excretory pore posterior to oesophagus. Cervical alae with up to 5 longitudinal folds anteriorly, contracting to single pair small bifid alae towards base of oesophagus; lateral alae absent.

Male: (holotype) Body length 2.1 mm, width 75. Oesophagus length 140; oesophageal bulb 40 long by 37.5 wide. Nerve ring 45 from anterior end, excretory pore not seen. Mamelon, without thick muscular body wall, 470 from posterior end, 35 long. Spicule 50, gubernaculum 25 long, unornamented; accessory piece not seen. Cloacal papillae; 2 pairs small pre cloacal, 1 pair large post cloacal. Tail conical, without spike, 75 long.

Female: (measurements of 10 specimens) Body length 3.8–4.9 (4.3) mm, width 182–315 (242). Oesophagus 300–382 (336). Nerve ring not seen; excretory pore 440–850 (576) from anterior end. Tail tapered, conical tip, 380–516 (468) long. Eggs oval, asymmetrical, with small lateral operculum, embryonated in utero, 135–142 (139.3) by 35–43 (41.1).

Remarks. The tribe is characterized by the symmetry of the buccal opening and lips, the arrangement of the genital papillae in a square, the lack of accessory cloacal papillae, the elongated form of the gubernaculum, the accessory piece split in two, the rugose areas of the mamelons with transverse grooves and the morphology of the egg, with a lateral operculum and length equal to or more than 2.5 times the width ( Hugot 1988). The new genus can be assigned to the Syphaciini on the basis of these shared characteristics. Pogonomicola n. g. can be differentiated from each of the other five congenerics by the form of the cervical alae, with numerous folds and the single, weakly defined mamelon. Pogonomicola can be further differentiated from Syphabulea in having neither three mamelons, nor the posteriorly extended vaginal cuticle, nor eggs with a large operculum; from Syphacia in having neither two or three mamelons nor a male tail with a long tip; from Syphatineria in having neither two mamelons nor cephalic papillae widely spaced; from Sypharista in having neither sexual dimorphism of the cephalic structures nor a different arrangement of the cephalic papillae ( Hugot 1988). Pogonomicola can be further differentiated from Lorentzicola by the morphology of the cephalic structures, the form of the oesophagus and the number of mamelons ( Smales 2010).

This is the third syphaciin genus to be recorded from New Guinean rodents; Syphacia is a cosmopolitan genus while Lorentzicola and Pogonomicola have been found only in New Guinea.

The hosts of Pogonomicola rugala , Pogonomys loriae and P. sylvestris , are old endemic species with origins from about 5.5 million years ago ( Rowe et al. 2008) and have altitudinal distributions that may overlap between 1000 and 2000 m ( Musser & Carleton 2005). Infection of these hosts by Pogonomicola rugala is congruent with Hugot’s (1990) suggestion that the Syphaciini are a monophyletic group in which speciation events are associated with isolation in host groups. The unique morphological features of P. r u g a l a, including multifolded cervical alae and a single, weakly developed mamelon, may therefore have evolved during a long association with its hosts.

Figures

FIGURES 1 – 10. Pogonomicola rugala n. gen., n. sp. 1. Adult male, lateral view, arrow indicating weakly defined mamelon; 2. Cervical end, female, showing longitudinally folded cervical alae; 3. Cephalic plate, female; 4. Anterior end, female; 5. Cervical ala, female, transverse section at level of base of oesophagus; 6. Cervical alae, transverse sections, female 1, showing variable nature of folding; 7. Vulva, lateral view; 8. Cervical alae, transverse sections, female 2, showing variable nature of folding; 9. Egg; 10. Posterior end, female. Scale bars: 1, 2, 10, 100 µm; 3, 5, 8, 9, 25 µm; 4, 200 µm; 6, 7, 50 µm.