Austrostrongylus aggregatus Johnston & Mawson, 1940

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 : 4-5

Austrostrongylus aggregatus Johnston & Mawson, 1940

( Figs. 1–3)

Type material: holotype ♂, allotype ♀, Milson Island , New South Wales, coll. J.B. Cleland, Dec. 1909, SAM 42890–1 ; paratypes, 6 ♂♂, 6 ♀♀ (examined from hundreds in vial) ( SAM 1818 ) .

Type host: Wallabia bicolor (Desmarest) .

Site in host: small intestine.

Material examined: From Wallabia bicolor : New South Wales: types; 3 ♂♂, Nowra ( SAM 45759) ; Queensland: 1 ♂, 1 ♀, Charters Towers ( SAM 32947) ; 10 ♀♀, Logan Village ( SAM 5461 ) .

Redescription. Anterior part of body: ( Fig. 1A–D) interno-labial papillae not seen; excretory pore and deirids slightly anterior to oesophago-intestinal junction.

Male: (measurements of 5 specimens) length 3.53–4.40 (3.91) mm; maximum width 108–138 (118); length of cephalic vesicle 69–77 (72); length of oesophagus 308–346 (329); nerve ring, deirids and excretory pore 169, 308 and 315 (n=1) from anterior end respectively. Spicules 646–967 (800) long, calomus 108–123 (118), lamina 538–723 (625); gubernaculum 54–62 (58) long. Bursa sub-symmetrical; pattern of rays of 1– 4 type in both lobes with rays 3 diverging first from common trunk of rays 3–6; rays 4–6 diverging at same level ( Fig. 1N); rays 8 arising from base of dorsal ray; dorsal ray dividing in distal quarter in two branches, each branch terminating in 3 digitiform branchlets, phasmids shorter than remaining lateral pairs of branchlets; external branchlet (rays 9) of similar length to internal branchlet (rays 10) ( Fig. 1O). Genital cone prominent, papillae 7 paired on small, conical projections ( Fig. 1 J, K). Spicules needle-like, straight, simple ( Fig. 1E), pale yellow in colour; tips bifid, enlarged in lateral view, curved laterally in median views, enclosed in small rounded terminal ala ( Fig. 1F, G). Gubernaculum poorly sclerotised, slender, elongate in lateral view ( Fig. 1I), oval in median view ( Fig. 1H).

Female: (measurements of 5 specimens) length 3.67–4.73 (4.31) mm; maximum width 100–154 (132); length of cephalic vesicle 62–85 (73); length of oesophagus 285–354 (323); nerve ring and excretory pore 192 and 276–269 (273) from anterior end respectively. Vulva 432–615 (492) from posterior end; vagina vera long, directed anteriorly ( Fig. 1M); measurements from single female: vagina vera 346 long, vestibule 100 long; anterior and posterior sphincters 50 and 42 long, anterior infundibulum 117 long, posterior infundibulum 133 long; 4–7 (6) eggs in anterior uterus, 4–7 (5) in posterior uterus; eggs 73–77 (74) long, 31–46 (39) wide; tail 81–100 (89) long with attenuated extremity 15–23 (20) long ( Fig. 1L).

Synlophe: Studied in paratypes ( SAM 1818 ). Oesophageal region of body studied in 1 ♂ 4.0 mm long and 1 ♀ 4.6 mm long. Median and distal thirds of body studied in 1 ♂ 4.1 mm long and 1 ♀ 4. 5 mm long .

In both sexes, ridges arising between posterior margin of cephalic vesicle and level of excretory pore, except ridge 1 which appears just posterior to oesophago-intestinal junction ( Figs. 2E, 3E); ridges disappearing in distal sixth of body in male and from end of third quarter of body onwards in female, except ridge 5’ which disappears at beginning of second quarter in both sexes.

At mid-body, right float prominently pedunculate ( Figs. 2F, 3F). Floats of similar size at level of oesophagointestinal junction, then right float less well developed posteriorly. In male, size of right float increasing up to midbody then decreasing regularly down to about 150 µm anterior to caudal bursa where it disappears ( Fig. 2K). Size of left float increasing up to distal five sixths of body ( Fig. 2H) then decreasing down to caudal bursa. In female, size of right float increasing to mid-body then decreasing and disappearing between vulva and tail ( Fig. 3K). Size of left float increasing up to mid-body ( Fig. 3F) then decreasing to tail but not disappearing ( Fig. 3L).

Number and orientation of cuticular ridges at oesophago-intestinal junction: 7 (1 dorsal, 6 ventral) ( Figs. 2D, 3D); posterior to oesophago-intestinal junction 8 ridges (2 dorsal, 6 ventral) ( Figs. 2E, 3E); at mid-body 7 (2 dorsal, 5 ventral) ( Figs. 2F, 3F) due to loss of ridge 5’. At mid-body, single axis of orientation inclined at 65 to sagittal axis in both sexes ( Figs. 2F, 3F).

Sequence of origin of ridges: from posterior margin of cephalic vesicle to about 40 µm posterior to oesophagointestinal junction: in male, ridges 2’, 3’, 4’, 2 ( Fig. 2A) then 1’, 5’ ( Fig. 2B), then 6’ ( Fig. 2C), then 1 ( Fig. 2E); in female, ridges 2’, 3’, 4’, 2 ( Fig. 3A), then 1’, 5’ ( Fig. 3B), then 6’ ( Fig. 3C), then 1 ( Fig. 3E).

Sequence of disappearance of ridges: in both sexes, ridge 5’ at beginning of second quarter of body; then, in male from 550 to 100 µm anterior to caudal bursa (from 650 to 200 µm from caudal extremity), ridges, 4’, 1 ( Fig. 2G), then 2’ ( Fig. 2H), then 1’, 3’, 6’ ( Fig. 2I), then 2 ( Fig. 2J); in female, from 800 µm anterior to vulva to 500 µ m posterior to vulva (1.3 mm to 350 µm anterior to caudal extremity), ridge 1 ( Fig. 3G), then 4’ ( Fig. 3H), then 1’, 2’, 6’ ( Fig. 3I), then 3’, 2 ( Fig. 3J).

Position of left ridge 1’: in male, ridge 1’ arising in dorsal position, situated in front of left lateral field at midbody, then migrating slightly ventrally; in female, in same position until ridge disappears.

Remarks. This species, first described by Johnston & Mawson (1940a) was redescribed by Mawson (1973) from the same host, W. bicolor . Although readily recognisable from the earlier descriptions, there is little detail of the synlophe, a deficiency which is addressed in the present re-description.

The type specimens, although abundant (>100), are dark brown in colour and were difficult to examine. Nonetheless, it was possible to base the redescription almost exclusively on type specimens. The only features illustrated from additional specimens were the spicules as their full extent was not clearly visible in the types.

An additional collection ( SAM 2654 ) labelled as A. aggregatus with the locality recorded simply as "southern Queensland " consisted of five females and pieces of nematodes. The specimens are dark brown in colour, obscuring internal details and it was not possible to confirm the identity of this collection .

The additional collections listed here extend the known range of the species to north Queensland (Charters Towers) and to the south coast of New South Wales (Nowra).

The number of ridges in the synlophe reaches its maximum of 8 (2 dorsal, 6 ventral) in both sexes just posterior to the level of the oesophago-intestinal junction ( Figs. 2E, 3E) and at mid-body has 7 ridges (2 dorsal, 5 ventral) in both sexes ( Figs. 2F, 3F). In the male, ridges terminate 150 µm anterior to the bursa, at which level, the right float has disappeared. In the female, ridges are present anterior and posterior to the vulva and the floats are well developed anterior to the vulva. In the female of A. mawsonae n. sp., the maximum number of ridges is 7 (2 dorsal, 5 ventral) just posterior to the oesophago-intestinal junction due to the absence of ridge 5’ ( Fig. 12F)(see below).