Austrostrongylus mawsonae, Durette-Desset & Beveridge, 2012

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 : 18-23

Austrostrongylus mawsonae sp. nov.

( Figs. 10–12)

Types: holotype ♂, SAM 45752 ; allotype ♀, SAM 45753 ; paratypes, 15 ♂♂, 6 ♀♀ SAM 33993 , 45758.

Type locality: Healesville , Victoria, Australia .

Date of collection: 3.ii.1999.

Type host: Wallabia bicolor (Desmarest) .

Site in host: small intestine.

Etymology: this species is named after P.M. Mawson in appreciation of her earlier work on the genus.

Material examined: From Wallabia bicolor : Victoria: types; 1 ♂, 1 ♀, Leongatha ( SAM 45755) ; 1 ♂, 1 ♀, Kamarooka ( SAM 45656) ; 1 ♂, 1 ♀, Beaufort ( SAM 45466) ; 8 ♂♂, 8 ♀♀, Dixon's Creek ( SAM 45757) ; 2 ♂♂, Portland ( SAM 46275) .

Description: Anterior part of body: ( Fig. 10 A–D) labial papillae not seen; excretory pore and deirids anterior to oesophago-intestinal junction.

Male: (measurements of holotype) length 3.40 mm; maximum width 100; length of cephalic vesicle 69; length of oesophagus 284; excretory pore 390 from anterior end. Spicules 577 long, calomus 77, lamina 500; gubernaculum 54 long; (measurements of 5 specimens, paratypes) length 2.91–3.73 (3.36) mm; maximum width 63–92 (79); length of cephalic vesicle 53–77 (86); length of oesophagus 255–295 (284); nerve ring, deirids and excretory pore 117, 230 (n=1) and 210–300 (255) from anterior end respectively. Spicules 570–663 (616) long, calomus 96–115 (108), lamina 496–572 (544); gubernaculum 42–46 (44) long. Bursa markedly dissymmetrical, right lobe much larger than left lobe; bursal pattern of type 1-3- 1 in left lobe, of type 3-1- 1 in right lobe with ray 6 arising first on common trunk of rays 2–6; rays 2–4 diverging at same level ( Fig. 10K); right ray 4 greatly enlarged, much broader; rays 8 arising from base of dorsal ray; Right ray 9 originating first at mid-length ( Fig. 10J) then dorsal ray dividing in distal quarter, terminating in left ray 9 and a pair of digitiform branchlets, rays 10 ( Fig. 10K). Genital cone prominent, papillae 7 paired on small, conical projections ( Fig. 10L). Spicules needle-like, ( Fig. 10F), pale yellow in colour, with distal ends characteristically recurved in lateral views; tips not enclosed in rounded terminal enlargement ( Fig. 10 G, H). Gubernaculum poorly sclerotised ( Fig. 10 I), scarcely visible in median view.

Female: (measurements of allotype) length 4.33 mm; maximum width 108; length of cephalic vesicle 85; length of oesophagus 346; excretory pore 369 from anterior end. Vulva 533 from posterior end; tail 85 long, attenuated extremity 21 long; egg 77 x 38; (measurements of 5 specimens, paratypes) length 3.29–5.17 (4.59) mm; maximum width 74–138 (103); length of cephalic vesicle 68–85 (76); length of oesophagus 316–400 (353); deirid and excretory pore 438 (n=1) and 263–369 (304) from anterior end respectively. Vulva 392–474 (432) from posterior end ( Fig. 10M); measurements from single female: vagina vera 130 long, vestibule 95 long; anterior and posterior sphincters 35 and 33 long, anterior infundibulum 90 long, posterior infundibulum 115 long; 5–8 (6) eggs in anterior uterus, 4–5 (4.5) in posterior uterus; eggs 68–74 (66) long, 32–37 (35) wide; tail 77–98 (85) long, attenuated extremity 11 long ( Fig. 10E).

Synlophe: Studied in 1 male 3.2 mm long and 1 female 4 mm long (paratypes SAM 33993). In both sexes, ridges arising between posterior margin of cephalic vesicle and level of excretory pore; ridges disappearing in distal quarter of body in male, in distal third in female. Ridge 5’ entirely absent .

Right float with small peduncle at mid-body region ( Figs. 11F, 12G). In male and female, peduncle with prominent constriction at beginning of distal quarter of body in male ( Figs. 11G, H, I), at median third in female ( Figs. 12G, H). Floats of similar size at level of oesophago-intestinal junction and at mid-body, then right float less well developed. In male, size of right float increasing to mid-body then decreasing to about 200 µm anterior to bursa where it disappears ( Fig. 11K); size of left float increasing in size to 300 µm anterior to bursa ( Fig. 11J) then decreasing to 50 µm anterior to bursa ( Fig. 11L). In female, size of right float increasing up to mid-body then decreasing from distal quarter and disappearing between vulva and tail ( Fig.12 K); shape of right float varies along body; size of left float increasing to mid-body then decreasing to tail.

Number of ridges: in both sexes, 6 (2 dorsal, 4 ventral) ( Figs. 11E, 12D) at oesophago-intestinal junction and 7 at mid-body (2 dorsal, 5 ventral) ( Figs. 11F, 12G); at mid-body, single axis of orientation inclined at 70° to sagittal axis in male, 60° in female ( Figs. 11F, 12G).

Sequence of origin of ridges: from posterior of cephalic vesicle to level of excretory pore: in male, ridges 2’, 3’, 4’ ( Fig. 11A), then 6’, 1 ( Fig. 11B), then 1’, 2 ( Fig. 11C); in female, ridges 2’, 3’, 4’, 1 ( Fig 12A), then 6’ ( Fig. 12B), then 2 ( Fig. 12C), then 1’ ( Fig. 12D).

Sequence of disappearance of ridges: in male, from 650 µm to 50 µm anterior to bursa (750 µm anterior to caudal extremity): ridge 4’ ( Fig. 11G), then 1’ ( Fig. 11H), then 1 ( Fig. 11I), then 2’, 2 ( Fig.11J), then 3’ ( Fig. 11K); in female, from 1.5mm to 100 µm anterior to vulva, ridges 1’, 4’ ( Fig. 12H), then 1 ( Fig. 12I), then 2’, 3’,6’, 2 ( Fig. 12K).

Position of left ridge 1’: arising slightly dorsal to frontal axis; at mid-body, situated in front of left lateral field in both sexes, migrating slightly ventrally in male; in same position until disappearance in female.

Remarks. This species is most similar to A. aggregatus in having long, needle-like spicules and in having an elongate vagina vera. It is readily distinguishable however in the characteristics of the bursa which is highly dissymmetrical and with a grossly enlarged ray 4 on the right hand side of the bursa while the bursa of A. aggregatus is sub-symmetrical. The two species are also distinguishable by subtle differences in the spicule tips. Those of A. mawsonae are characteristically recurved ventrally at the tip and are truncated rather than ending in a slight terminal enlargement as in A. aggregatus . The new species is also distinguished from A. aggregatus in having four terminal branches to the dorsal ray rather than the six seen in A. aggregatus .

The number of ridges in the synlophe reaches its maximum of 7 (2 dorsal, 5 ventral), in the male, posterior to the oesophago-intestinal junction ( Fig. 11E) and just before this junction in the female ( Fig. 12D); at the oesophago-intestinal junction, there are 6 ridges (2 dorsal, 4 ventral) in both sexes ( Figs. 11D, 12E); at mid-body there are 7 ridges (2 dorsal, 5 ventral) in both sexes ( Figs. 11F, 12G). Ridge 5’ is entirely absent.

Ridges disappear in the posterior third of the body. In the male, ridges terminate 50 µm anterior to the bursa, at which level, the both floats have disappeared ( Fig. 11L). In the female, ridges are absent anterior to the vulva ( Figs. 12K) at which level, the right float is absent and the left float is present ( Fig. 12K). The left float disappears between the vulva and the anus.

Ridge 4’ disappears between the level of the excretory pore and 200 µm posterior to the oesophago-intestinal junction in male and between the level of the oesophago-intestinal junction and 300 µm posterior to this junction in the female. However, the synlophe was studied in one male and one female only and more specimens need to be examined to ensure that this character is specific. Differences in the synlophe of females of A. aggregatus and A. mawsonae have been discussed above.

This species was found only in Wallabia bicolor in Victoria and was usually greatly outnumbered by A. victoriensis such that it could easily be overlooked in heavy infections. Even at the type locality, Healesville, the species was only recovered from two of the 12 wallabies examined from that locality. Current records suggest that this species parasitises W. bicolor in the southern part of the host’s range (Victoria), while A. aggregatus occurs in the more northern part of its range (New South Wales and Queensland).