Austrostrongylus victoriensis Cassone, 1983

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 : 28-32

Austrostrongylus victoriensis Cassone, 1983

( Figs. 16–18)

Type material: holotype ♂, Healesville , Victoria, 2.vi.1975, coll. I. Beveridge, SAM V1319 , allotype ♀, same data, SAM V 1320 ; paratypes, same data SAM V1321, MNHN 809 CA .

Type host: Wallabia bicolor (Desmarest) .

Site in host: small intestine.

Material examined: From Wallabia bicolor : Victoria: types; 1 ♂, Dixon's Creek ( SAM 22935) ; 7 ♂♂, 7 ♀♀, Phillip Island ( SAM 24596) ; 6 ♂♂, 2 ♀♀, Kamarooka ( SAM 31084) ; 7 ♂♂, 1 ♀, Lakes Entrance ( SAM 27327) ; 10 ♂♂, 10 ♀♀, Brisbane Ranges ( SAM 18761, 19252 ) ; 31 ♂♂, Traralgon Creek ( SAM 23153) ; 21 ♂♂, 10 ♀♀, Buangor ( SAM 6687 , 33975 ) ; 131 ♂♂, Healesville ( SAM 10114, 32038 , 32041 , 33995 ) ; 73 ♂♂, 27 ♀♀, Dartmouth ( SAM 9516 , 9531 , 12125 , 13711 ) ; 1 ♂, 1 ♀, Bacchus Marsh ( SAM 10019) ; 4 ♀♀, Bellbird Creek ( SAM 9700 ) ; 3 ♀♀, Marlo Plains ( SAM 9695 ) ; 1 ♂, 2 ♀♀, Bend of Islands ( SAM 9257 ) ; 1 ♂, 6 ♀♀, Leongatha ( SAM 8005 ) ; 5 ♂♂, 5 ♀♀, Sunday Island ( SAM 17598) ; 5 ♂♂, Mitta Mitta ( SAM 12095) ; 5 ♂♂, 5 ♀♀, Marysville ( SAM 11577) ; 10 ♂♂, Teesdale ( SAM 10754) ; 2 ♂♂, Hopper's Crossing ( SAM 34650) ; 8 ♂♂, Werribee ( SAM 34672) ; 10 ♂♂, 13 ♀♀, Portland ( SAM 46273) ; New South Wales: 2 ♂♂, Nowra ( SAM 45744) ; 2 ♂♂, Milson Island ( SAM 45754) .

Redescription: Anterior part of body: ( Fig. 16A–C) labial papillae not seen; excretory pore and deirids just anterior to oesophago-intestinal junction.

Male: (measurements of 5 specimens) length 5.98–7.01 (6.28) mm; maximum width 110–170 (150); length of cephalic vesicle 70–80 (75); length of oesophagus 310–370 (340); deirids, nerve ring and excretory pore 310–370 (340), 175–240 (208) and 290–360 (330) from anterior end respectively. Spicules 230–310 (270) long, calomus 85–105 (95), lamina 200–250 (225); gubernaculum 40–65 (52) long. Bursa symmetrical; bursal pattern of type 1–4 in both lobes with right ray 3 diverging at same level as right ray 6 and left ray 3 proximally to left ray 6; right ray 2 much thicker than left; right ray 4 more robust than left ray; rays 8 arising from common trunk of rays 2–6; dorsal ray very short; rays 9 arising asymetrically on dorsal ray, right ray 9 arising first; then dorsal ray branching in distal quarter with 2 branchlets, each branchlet branching in distal quarter with elongate, digitiform external pair (rays 10) and usually with short internal pair (phasmid) ( Fig. 16F). Genital cone prominent; tip thickened and opaque but not heavily sclerotised; papillae 7 paired on tiny, conical projections Figs. 16G, H). Spicules, dark brown in colour, short; tips sharply pointed ( Fig. 16D). Gubernaculum well sclerotised, quadrangular in median view ( Fig. 16I, J).

Female: (measurements of 5 specimens) length 6.83–7.56 (7.04) mm; maximum width 110–150 (130); length of cephalic vesicle 80 (80); length of oesophagus 320–390 (360); deirids, nerve ring and excretory pore 300–330 (320), 175–230 (205) and 270–320 (300) from anterior end respectively. Vulva 280–360 (330) from posterior end; ( Fig. 16E); measurements from single female: vagina vera 40 long, vestibule 80 long, anterior sphincter 30 long, posterior sphincter 25 long, anterior infundibulum 78 long, posterior infundibulum 125 long; 2–8 (6) eggs in anterior uterus, 1–4 (2) in posterior uterus; eggs 70–75 (73) long, 40–55 (47) wide; tail 60–90 (77) long, conical with attenuated extremity ( Fig. 16E); phasmids not visible.

Synlophe : Entire body studied in 1 male, 3 mm long. Oesophageal region of body and median third studied in 1 female 3.7 mm long, distal third in 1 female 4.6 mm long ( SAM 10114) .

In both sexes, ridges arising between posterior margin of cephalic vesicle and 50 µm posterior to oesophagointestinal junction. In male, ridges disappearing in distal third of body except ridge 5’ which disappears at end of median third of body. In female, ridges disappearing in distal third of body.

Right float with well-developed peduncle at mid-body ( Figs. 17F, 18F). Floats of similar size at oesophagointestinal junction and at mid-body in male. Size of right float increasing to mid-body, remaining constant to about 800 µm anterior to bursa, then decreasing in size and disappearing about 500 µm anterior to bursa ( Fig. 17K). Size of left float increasing to about 500 µm anterior to bursa, then decreasing in size and disappearing at about 40 µm anterior to bursa ( Fig. 17L). In female, size of right float increasing along two-thirds of body then decreasing to 100 µm anterior to vulva ( Fig. 18M); size of left float increasing to mid-body then decreasing to 40 µm anterior to vulva ( Fig. 18N).

Number of ridges: in both sexes 7 (1 dorsal, 6 ventral) at oesophago-intestinal junction ( Figs. 17D, 18D) and 8 (2 dorsal, 6 ventral) at mid-body ( Fig. 17F, 18F). At mid-body, single axis of orientation inclined at 75° to sagittal axis in male, at 60° in female.

Sequence of origin of ridges: in both sexes, from posterior margin of cephalic vesicle to 50 µm posterior to oesophago-intestinal junction; in male, ridges 2’ 3’, 4’, 5’ 2 ( Fig. 17A), then 6’ ( Fig. 17B), then 1’ ( Fig. 17C), then 1 ( Fig. 17E). In female, ridges 2’, 3’, 4’ ( Fig. 18B), then 5’, 2 ( Fig. 18C), then 1’, 6’ ( Fig. 18D), then 1 ( Fig. 18E).

Sequence of disappearance of ridges: in male, ridge 5’ at end of median third ( Fig. 17G) then between 850 µm and 40 µm anterior to bursa (950 µm to 140 µm anterior to caudal extremity) ridges 4’, 1 ( Fig. 17H), then 1’ ( Fig. 18I), then 6’, 2 ( Fig. 17J), then 2’, 3’ ( Fig. 17L). In female, between 400 µm anterior to vulva (700 µm anterior to caudal extremity) and 140 µm anterior to vulva, ridges 4’, 5’ ( Fig. 18G), then 1 ( Fig. 18H), then 1’ ( Fig. 18I), then 2’ ( Fig. 18J), then 6’, 2 ( Fig. 18K), then 3’( Fig. 18L).

Position of left ridge 1’: arising slightly dorsally ( Figs. 17C, 18D) then migrating ventrally; situated opposite lateral cord at mid-body ( Figs. 17F, 18F) then slightly ventral to cord in posterior part of body ( Figs. 17H, 18H).

Remarks. An excellent description of this species was provided by Cassone (1983). However, the description of the synlophe was based on a single transverse section of each sex and as a consequence contains insufficient detail for comparison with other species. A fuller description of the synlophe is provided here.

The number of ridges in the synlophe reaches its maximum of 8 (2 dorsal, 6 ventral) just posterior to oesophago-intestinal junction in both sexes; at the oesophago-intestinal junction, there are 7 ridges (1 dorsal, 6 ventral) in both sexes ( Figs. 17D, 18D); at mid-body there are 8 ridges (2 dorsal, 6 ventral) in both sexes ( Figs. 17F, 18F).

Ridges disappear in the distal third of the body in the male and in the distal quarter in the female, except ridge 5’ which disappears at the end of the median third of the body in the male. In the male, ridges terminate anterior to the bursa, at which level, the both floats have disappeared ( Fig. 17L). In the female, ridges are absent anterior to the vulva at which level, the both floats are absent ( Fig. 18N).

Cassone (1983) reported the species from a single locality in Victoria, but Beveridge et al. (1985) found it to be relatively widely distributed in W. bicolor in Victoria. Current records extend its geographical range northwards as far as Milson Island in the Hawkesbury estuary, just north of Sydney, while the parasite appears to be absent in W. bicolor in Queensland ( Beveridge et al., 1998). Aussavy et al. (2011) reported the species in 60% of 10 W. bicolor examined in the Grampian Ranges of Victoria, but failed to recover the species from sympatric hosts ( M. fuliginosus , M. giganteus , M. rufogriseus ) suggesting a relatively high degree of host specificity.