Macroponema obendorfi Beveridge, 2020

Sukee, Tanapan, Jabbar, Abdul & Beveridge, Ian, 2020, Revision of MaCroponema Mawson, 1978 (Nematoda: Strongylida) from macropodid marsupials with the description of two new species, Parasites & Vectors (298) 13 (1), pp. 1-21 : 14-17

Macroponema obendorfi Beveridge n. sp.

Syn. Macroponema cf. comani of Tan et al. (2012)

Type-host: Osphranter robustus woodwardi (Thomas) (Marsupialia: Macropodidae ).

Additional host: Osphranter antilopinus (Gould) (Marsupialia: Macropodidae ).

Type-locality: Mount Smith (13°31 ′ S, 131°7 ′ E), Northern Territory, Australia .

Type-material: Holotype ♂ ( SAM AHC 48936 ); allotype ♀ ( SAM AHC 48937 ); 16 paratypes: 7♂♂ and 9 ♀♀ ( SAM AHC 48938 ).

Additional material examined: From O. robustus woodwardi : Northern Territory: 1♂, 4♀♀, Katherine ( SAM AHC 32700 , 48883 ) ; 2 ♂♂, 4 ♀♀, Newry Station via Timber Creek ( SAM AHC 44339 ) . From O. antilopinus : Northern Territory: 1♂, 1♀, Katherine ( SAM AHC 32710 ) ; Western Australia: 5 ♀♀, Napier Downs Station via Derby ( SAM AHC 48884 ) ; 2 ♀♀, Camp Creek , Mitchell Plateau ( SAM AHC 6162 ) .

Representative DNA sequences: Molecular voucher from O. robustus (Newry Stn via Timber Creek; SAM 46097 ) : GenBank : HE775532 ( ITS 1 , 5.8 S and ITS 2 ) .

Etymology: Named after Dr D. L. Obendorf, who helped collect much of the original material upon which the description of M. beveridgei and the genus was based.

Description

General. Robust, whitish nematodes; cephalic collar absent; mouth dorso-ventrally elongate; elevation on each side of mouth opening bears lateral amphid and 2 dome-shaped sub-median papillae; papillae with 2 short, anteriorly-directed setae; buccal capsule elongate, dorso-ventrally elongate, poorly sclerotised, with partially sclerotised annulus in anterior half; buccal capsule supported externally by strong radial musculature in posterior half; non-sclerotised annulus at junction of buccal capsule with oesophagus; oesophagus elongate; corpus widening posterior to nerve-ring; posterior half of corpus with c.12–14 sets of bead-like sclerotised projections in lining, one arising from each sector of oesophagus; isthmus narrow, elongate; bulb elongate; intestinal cells enlarged at anterior extremity, surrounding posterior extremity of oesophageal bulb. Nerve-ring in anterior oesophageal region; excretory pore at level of oesophageal bulb or anterior to it; deirids at level of buccal capsule.

Male [Measurements of 10 specimens; Figs. 46–52.] Total length 8.3–11.1 (10.3); maximum width 0.42–0.63 (0.50); buccal capsule 0.09–0.13 (0.12) long, 0.04–0.07 (0.06) wide; oesophagus 2.45–2.72 (2.52); nerve-ring from anterior extremity 0.45–0.63 (0.58); excretory pore from anterior extremity 1.98–2.45 (2.28); deirid from anterior extremity 0.08–0.14 (0.11). Bursal lobes poorly separated; lateral lobes slightly longer than ventral and dorsal lobes; no indentation in dorsal lobe; ventro-ventral and ventro-lateral rays apposed, reaching margin of bursa; externo-lateral ray divergent from lateral trunk, not reaching margin of bursa; medio-lateral and postero-lateral rays apposed in distal half, fused in proximal half, reaching margin of bursa; externo-dorsal ray arising from lateral trunk, slender, not reaching margin of bursa; dorsal ray slender at origin, divides at mid-length; branches arcuate, internal branchlets reaching margin of bursa; external branchlets very short, arise soon after principal bifurcation, terminate in elevations on internal surface of bursa. Spicules elongate, alate; alae with numerous, fine, transverse striations; anterior extremity irregularly knobbed; distal extremity blunt tipped; alae terminate abruptly anterior to spicule tip, lose striations prior to termination; spicule length 1.43–1.80 (1.66); gubernaculum absent; central cordate and paired lateral thickenings of spicule sheaths present. Ventral lip of genital cone large, conical, bearing papilla 0; dorsal lip with paired bifid appendages.

Female [Measurements of 10 specimens; Figs. 53, 54.] Total length 11.3–13.8 (13.1); maximum width 0.69–0.80 (0.74); buccal capsule 0.10–0.15 (0.12) long, 0.05–0.07 (0.06) wide; oesophagus 2.60–3.36 (2.94); nerve-ring from anterior extremity 0.62–0.73 (0.67); excretory pore from anterior extremity 2.15–3.30 (2.72); deirid from anterior extremity 0.08–0.17 (013). Tail short, conical, straight, 0.35–0.48 (0.42) long; vulva 0.90–1.41 (1.02) from tip of tail; vagina short, 0.45–0.73 (0.65) long, slightly sinuous; eggs not seen.

Remarks

This species was initially identified as M. cf. comani by Tan et al. [ 4] based on molecular differences and a difference in host distribution with M. comani restricted to Ma. giganteus and M. cf. comani occurring in O. r. woodwardi . The metrical morphological data included in that study [ 4] indicated no obvious differences between the populations of M. comani distinguishable using molecular methods. In the present morphological study, a few features were identified to separate M. comani occurring in Ma. giganteus from the closely related species, here identified as M. obendorfi n. sp. occurring in O. robustus . The simplest feature to observe is the number of groups of bead-like sclerotised projections in the oesophagus which range from 12 to 14 in M. obendorfi n. sp. compared with 20 in M. comani . There are slight differences in the mean spicule length (1.66 mm in M. obendorfi n. sp. vs 1.81 mm in M. comani ) but there is considerable overlap. The two species also share the unusual feature of having the medio-lateral and postero-lateral rays fused in the proximal region and apposed only in their distal regions, in contradistinction to the two rays being apposed along their entire lengths in the remaining species. The two species appear to be very similar morphologically with no additional differences noted apart from the numbers of groups of sclerotised beads lining the oesophagus and the anomalous host and geographical distribution ( Fig. 55 ).

Figures

Fig. 55 Distribution of Macroponema obendorfi n. sp.in Osphranter robustus and O. antilopinus in northern Australia.Closed circles represent localities at which the parasite has been collected from O. robustus; open circles indicate locations at which common wallaroos have been examined but the nematode has not been found; closed squares represent localities at which the parasite has been collected from O.antilopinus; open squares indicate locations at which antilopine wallaroos have been examined but the nematode has not been found