Austrostrongylus chandleri Mawson, 1973

Durette-Desset, M. C. & Beveridge, I., 2012, Redescriptions and descriptions of new species of Austrostrongylus Chandler, 1924 (Nematoda: Trichostrongylina), from Australian marsupials with a comparative study of features of the synlophe, Zootaxa 3512, pp. 1-41 : 9-13

Austrostrongylus chandleri Mawson, 1973

( Figs. 4–6)

Type material: holotype ♂, allotype ♀, Logan Village , Qld, coll. M.J.Mackerras ( SAM 41516) ; paratypes, 1 ♂, 1 ♀ ( SAM 5460 ) ; 25 ♂♂, 17 ♀♀, same collection data, not formerly designated as paratypes ( SAM 5463 ) .

Type host: Macropus rufogriseus (Desmarest) .

Other hosts: M. fuliginosus (Desmarest) , M. giganteus Shaw , Wallabia bicolor (Desmarest) .

Site in host: small intestine.

Material examined: From Macropus rufogriseus : Queensland: types; 3 ♂♂, Warwick ( SAM 45712) ; 8 ♂♂ Emuvale ( SAM 45713) ; 22 ♂♂, Logan Village ( SAM 6877 , 45714 ) ; Victoria: 28 ♂♂, Laharum ( MNHN 585 MQ, SAM 45718) , 2 ♂♂, Wartook ( SAM 45719) ( SAM 45465) ; 6 ♂♂, Brimpaen ( SAM 45720) ; 1 ♂, Casterton ( SAM 45711) ; 2 ♂, Portland ( SAM 45607) ; South Australia: 3 ♂♂, Joanna ( SAM 45710) ; Tasmania: 2 ♂♂, Waterhouse ( SAM 45709) ; 1 ♂, Sassafrass ( SAM 45748) .

From Macropus giganteus : Tasmania: 4 ♂♂, Maria Is. ( SAM 45751) ; Victoria: 4 ♂♂, Wartook ( SAM 45465) ; 1 ♂, Brimpaen ( SAM 45897) .

From Macropus fuliginosus : Victoria: 3 ♂♂, Brimpaen ( SAM 45898) .

From Wallabia bicolor : Queensland: 5 ♂♂, Logan Village ( SAM 5464 , 6734 ) ; New South Wales: 2 ♂♂, Nowra ( SAM 45743) ; Victoria: 1♂, Portland ( SAM 46274) .

Redescription: (based on specimens from Macropus rufogriseus )

Anterior part of body: ( Fig. 4 A–C) labial papillae not seen; excretory pore and deirids slightly anterior to oesophago-intestinal junction.

Male: (measurements of 5 specimens) length 5.27–6.22 (5.76) mm; maximum width 98–130 (115); length of cephalic vesicle 76–92 (86); length of oesophagus 326–380 (352); nerve ring, deirids and excretory pore 239–293 (259), 337–380 (352) and 293–391 (339) from anterior end respectively. Spicules 421–474 (444) long, calomus 105–152 (136), lamina 216–322 (290); gubernaculum 38–50 (41) long. Bursa slightly dissymmetrical with right lobe slightly larger than left lobe, ( Fig. 4M); pattern of rays of 1– 4 type in both lobes with right ray 3 diverging more proximally than ray 6 and right ray 3 diverging slightly more distally; rays 4 thickest; rays 8 arising from common trunk with rays 2–6; rays 9 (externo-dorsal branches) recurved arising in anterior third of dorsal ray, then dorsal ray dividing into 2 branches near its extremity, each branch terminating in 2 tiny, digitiform branchlets, internal (phasmid) and external (rays 10) sometimes dissimilar in length. Genital cone prominent; papillae 7 paired on small, conical projections ( Fig. 4F, G). Spicules simple with almost imperceptible differentiation between calomus and lamina ( Fig. 4E), yellow in colour; tips bifid enclosed in rounded terminal ala ( Fig. 4D). Gubernaculum poorly sclerotised, sub-triangular in median view ( Fig. 4H).

Female: (measurements of single specimen) length 5.6 mm; maximum width 142; length of cephalic vesicle 74; length of oesophagus 421; nerve ring and excretory pore 263 and 342 from anterior end respectively. Vulva 2.14 mm from posterior end; vagina vera 80 long, ( Fig. 4L); vestibule 132 long, anterior and posterior sphincter 53 long, anterior and posterior infundibulum 100 long; eggs 79 long, 42 wide; tail 95 long with attenuated extremity 18 long ( Fig. 4J).

Synlophe: In male, oesophageal and median third of body studied in 1 male 6.0 mm long, distal third in 1 male 6.1 mm long. Entire body studied in 1 female 5.6 mm long.

In both sexes, cuticular ridges arising between posterior margin of cephalic vesicle and excretory pore and disappearing in distal third of body except ridge 5’ which disappears in male about 400 µm anterior to mid-body region ( Fig. 5F), and in female 450 µm posterior to mid-body (Fig, 6H). In female, distal quarter lacks ridges (about 400 µm anterior to vulva).

At oesophago-intestinal junction, peduncle of right float well developed, particularly in female ( Figs. 5E, 6F). At mid-body, peduncle reduced in both sexes ( Figs. 5F, 6G). Floats of similar size at level of oesophago-intestinal junction, then right float less well developed than left float. In male, size of right float increasing up to level of oesophago-intestinal junction, then decreasing and disappearing 600 µm anterior to bursa (800 µm anterior to caudal extremity) ( Fig. 5L). In female, size of right float increasing to proximal third of body then decreasing to about 900 µm anterior to vulva ( Fig. 6L) where it disappears. In male, left float increasing in size up to its disappearance just anterior to bursa ( Fig. 5N). In female, left float increasing in size to oesophago-intestinal junction, then remains more or less constant to level of vulva. Left float disappearing between vulva and anus.

Number of ridges: at oesophago-intestinal junction: 8 (2 dorsal, 6 ventral) in both sexes ( Figs. 5E, 6F); at midbody in male: 7 (2 dorsal, 5 ventral) ( Fig. 5F); at mid-body in female: 8 ( Fig. 6G) (2 dorsal, 6 ventral). At midbody, single axis of orientation inclined at 70° to sagittal axis in male, 80° in female ( Figs. 5F, 6G).

Sequence of origin of ridges: from posterior margin of cephalic vesicle to excretory pore: in male, ridges 3’, 4’, 5’, 2 ( Fig. 5A), then 2’, 6’ ( Fig. 5B), then 1’ ( Fig. 5C), then 1 ( Fig. 5D). In female, ridges 3’, 4’, 5’ ( Fig. 6A), then 2 ( Fig.6B), then 2’ ( Fig. 6C), then 1’, 6’ ( Fig. 6D), then 1 ( Fig. 6E).

Sequence of disappearance of ridges: ridge 5’ in male, 400 µm anterior to mid-body ( Fig. 5F), in female, 450 µm posterior to mid-body ( Fig. 6H), then in male, at end of median third of body, ridge 1 ( Fig. 5G), then between 1.4 mm anterior to bursa (1.6 mm anterior to caudal extremity) and 600 µm anterior to bursa, ridge 1’ ( Fig. 5H), then 2, ( Fig. 5I), then 4’ ( Fig. 5J), then 2’ ( Fig. 5K), then 6’ ( Fig. 5L), then 3’ ( Fig. 5M). In female, between 1.4 mm anterior to vulva (2.2 mm anterior to caudal extremity) and 600 µm anterior to vulva: ridges 1’ ( Fig. 6I), then 1, 4’ ( Fig. 6J), then 2 ( Fig. 6K), then 6’ ( Fig. 6L), then 3’ ( Fig. 6M), then 2’ ( Fig. 6N).

Position of left ridge 1’: arises in dorsal position ( Figs. 5C, 6D) then migrates ventrally; situated in front of left lateral cord at mid-body in male ( Fig. 5F) and at level of oesophago-intestinal junction in female ( Fig. 6F); same position is maintained until its disappearance.

Remarks. The general features of this species were well described by Mawson (1973) and it is readily recognisable by its slender yellow spicules and enlarged spicule tips.

The number of ridges in the synlophe reaches its maximum of 8 (2 dorsal, 6 ventral) in both sexes at the level of the excretory pore ( Figs. 5D, 6E) and at mid-body it has 7 ridges (2 dorsal, 5 ventral) in the male ( Fig. 5F) and 8 (2 dorsal, 6 ventral) in the female. Ridges disappear in the posterior quarter of the body. In the male, ridges terminate 600 µm anterior to the bursa, at which level, the right float has disappeared but the left float is still well developed ( Fig. 5M). In the female, ridges are absent 600 µm anterior to the vulva at which level, the right float has disappeared and the left float is poorly developed ( Fig. 6N). As the females of A. chandleri could only be identified definitively based on the features of the synlophe, only a single specimen was available for measurement.

The current collections substantially expand the known geographical range of the parasite to Victoria, New South Wales, South Australia and Tasmania, as well as adding M. giganteus as a new, if incidental, host. An additional collection from W. bicolor from Nowra, NSW confirms Mawson's observation (1973) that although primarily a parasite of M. rufogriseus , A. chandleri can also infect W. bicolor where the two host species co-occur. Aussavy et al. (2011) reported a prevalence of 46% of A. chandleri in M. rufogriseus in Victoria, with 10–11% prevalence in sympatric M. fuliginosus and M. giganteus . However, they did not find the species in the 10 W. bicolor they examined.