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IXODES TASMANI Neumann (possum tick, opossum tick)
Ixodes tasmani Neumann, 1899, pp. 144-5, fig. 20. Rainbow, 1906, p. 167. Nuttall and Warburton, 1911, pp. 244-5, figs. 239, 240. Nuttall, 1916, pp. 321-4, fig. 20. Ferguson, 1925, p. 28. Fielding, 1926, p. 41, fig. 11. Taylor and Murray, 1946, pp. 54-6, figs. 54, 55. Seddon, 1951, p. 143.
Ixodes (Endopalpiger) tasmani tasmani Schulze, 1935, p. 38.
Ixodes (Endopalpiger) tasmani victoriae Schulze, 1935, pp. 31. 38, fig. 35. Arthur. 1951 p. 163
Male
Fig. 15, a-h
Diagnosis
A small oval tick, with a well-defined, marginal body fold. article 1 of palpi enlarged, and extending towards base of mouthparts; hypostome dentition 2/2, scutum oval, punctations numerous, many relatively coarse and confluent: anal and adanal plates anteriorly and laterally straight, widest towards posterior margin of bodfemale coxae unarmed, and with membranous outgrowths on posterior margin.
Description
Body.-Oval, 2.5-3.0 mm by 1.6-1. 7 mm, narrowly rounded posteriorly, widest about mid-body region; marginal body fold well developed, extending from near a level with coxa IV, widening laterally and narrowing again posteriorlfemale hairs relatively few, small, and scattered.
Capitulum.-Short, about 0.36 mm in length; basis dorsally 0.32-0.35 mm wide, conspicuously punctate, posterior margin straight, posterolateral margins straight and divergent anteriorlfemale palpi wide apart, article 1 enlarged, rectangular dorsally, triangular ventrally, extending inwardly towards base of mouthparts, articles 2 and 3 indistinctly separated, 0.3 mm in length and twice as long as broad, narrower at base, otherwise of about equal width throughout the length.
Fig. 15.-I. tasmani, male: a, body (dorsal view); b, body (ventral view); c, hypostome; d, spiracular plate; e, capitulum (dorsal view); f, capitulum (ventral view); g, tarsus IV; h, tarsus I.
Hypostome 0.19 mm in length, somewhat spatulate, dentition with 2 rows of 4/4 small teeth distally, then 7 rows of 2/2 large teeth, with a few rows of 2/2 tiny, shallow, crowded, ridge-like teeth basally.
Scutum.-Elongate oval, 2.3-3.0 mm by 1.4-1.6 mm, convex, narrowly rounded posteriorly and widest in region between coxae III and IV; no lateral grooves or carinae; punctations very numerous, finer medianly, otherwise relatively coarse with some confluency, particularly anteriorlfemale cervical grooves somewhat shallow and punctate anteriorly, extending posteriorly as shallow divergent depressions; emargination moderate; scapulae bluntly pointed.
Genital aperture.-In second intercoxal space.
Ventral plates.-Pregenital plate hexagonal, broader than long; median plate, 1.0 by 0.6 mm, widest posteriorlfemale anal plate 0.7 by 0.3 mm, anterior margin straight, lateral margins straight and a little divergent; adanal plates 0.8 by 0.3 mm, slightly wider posteriorly than anteriorly, the external margins slightly curved convergentlfemale all plates with numerous punctations.
Spiracular plate.-Oval, 0.0.026 by 0.020 mm, the longer axis directed anteriorly.
Legs.-Slender, coxae contiguous, or almost so, increasing in size posteriorly, unarmed, with membranous outgrowths on posterior margins; tarsi tapering a little abruptlfemale tarsus 1 about 0.42-0.50 mm in length, tarsus I V about. 0.46-0.52 mm in length.
Fig. 16.-I. tasmani, female: a, capitulum (dorsal view); b, capitulum (ventral view); c, tarsus I; d, tarsus IV; e, scutum; f, anal grooves; g, spiracular plate; h, hypostome.
Female
Fig. 16, a-h
Diagnosis
A rather large tick on engorgement; the capitulum short, palpi broad, article 1 of palpi much enlarged and ensheathing base of mouthparts, porose areas oval, of moderate size, convergent anteriorlfemale hypostome spatulate, dentition variable but mainly 3/3; scutum a little wider than long and widest behind the middle, with numerous relatively coarse punctations; coxae unarmed, and with membranous outgrowths on posterior margin.
Description
Body.-Unfed specimens 2.4-2.6 mm by 1.4-1.6 mm, flat, oval, and widest .just anterior to spiracular plates; engorged specimens 8.0-11.8 mm by 5.0-5.6 mm, broadly ovoid; marginal groove in unfed specimens deep and complete, disappearing on engorgement; posterolateral and median grooves well defined: hairs small, scattered, sometimes almost lacking.
Capitulum.-Short, 0.48-0.66 min in length; basis dorsally 0.38-0.51 mm wide, posterior margin straight or slightly convex, posterolateral margins straight, a little divergent anteriorly, no cornua, but sometimes posterolateral angles somewhat swollen; porose areas well defined, moderate in size, usually oval, convergent anteriorly, the interval relatively narrow and forming a mild depression; basis ventrally with posterior margin a little convex, no auriculae; palpi short and broad, their bases widely separated, article 1 greatly enlarged, extending inwardly and anteriorly to ensheathe base of mouthparts, rectangular dorsally, ventrally triangular, and strongly salient laterally to be visible dorsally, the posterior margin extending to a point towards the mid-line over the anterior prolongation of coxa I ; articles 2 and 3 0.40-0.45 mm in length, narrow at base and broadening rapidly to a width of about one-third the length, sometimes finely granulated, apex rounded.
Hypostome short, 0.22-0.24 mm in length, spatulate, the apex broadly rounded; dentition with the teeth rather crowded, arrangement somewhat variable with 5-7 rows of 4/4 followed by 8-5 rows of 3/3, basally the teeth minute and sometimes 2/2; one specimen had 1 row of 4/4, 9 rows of 3/3 relatively large teeth on one side, and 8 rows of 4/4 and 2 rows of 3/3 relatively large teeth on the other.
Scutum.-Wider than long, 1.2-1.6 mm by 1.3-1.7 mm, and widest a little posterior to mid-length; convex; no lateral carinae; anterolateral margins straight or slightly sinuous, posterolateral margins mildly convex or slightly sinuous, the posterior angle very broad and rounded; punctations numerous, finer medianly and anteriorly, somewhat denser, coarser, and frequently confluent laterally, but sometimes relatively coarse throughout; cervical grooves well defined and convergent anteriorly, extending posteriorly as shallow divergent depressions, and usually attaining the posterolateral margins; emargination relatively deep; scapulae bluntly pointed.
Genital aperture.-In unfed specimens at level of coxa III but, as engorgement proceeds, moving towards second intercoxal space.
Genital grooves.-Well defined, divergent but curving convergently towards the posterior margin of the body.
Anal grooves.-Broadly convex anteriorly, then subparallel or curving gently convergently posteriorly to become divergent towards the posterior body margin.
Spiracular plate.-Small, ovoid, the longer axis transverse, 0.28-0.35 mm by 0.34-0.42 mm, the macula anterior to centre.
Legs.-Length moderate; coxae unarmed, flat, the posterior margins with membranous outgrowths; tarsi slender with relatively weak subterminal humps, tarsus I about 0.50-0.55 mm long, tarsus IV about 0.53-0.58 mm long.
Nymph
Fig. 17, a-g
Diagnosis
Scutum, palpi, and legs similar to those of female; hypostome dentition 2/2.
Description
Body.-Oval, 1.7-2.8 mm by 1.0-2.0 mm, with sparse, scattered, pale hairs.
Fig. 17.-I. tasmani, nymph: a, capitulum (dorsal view); b, capitulum (ventral view); c, spiracular plate; d, hypostome; e, scutum; J, tarsus I; g, tarsus IV.
Capitulum.-Length about 0.26 mm ; basis about 0.24 mm wide, sometimes a few punctations dorsally, the posterior and posterolateral margins straight, the latter a little divergent anteriorlfemale palpi with article 1 somewhat as in female, articles 2 and 3 about 0.17 mm long, broadening medianly, article 3 rounded apically, as broad as article 2, but not as long.
Hypostome rounded apically, about. 0.17 mm long, dentition 2/2 of about 8 teeth, the basal rows fine and delicate.
Scutum.-Broader than long, 0.53 by 0.76 mm; punctations, cervical grooves, emargination, and scapulae as in female.
Anal grooves.-Subparallel posteriorly in unfed specimens, but curving gently convergently in engorged specimens.
Spiracular plate.-Oval, the longer axis transverse, about 0.08 by 0.14 min.
Legs.-As in female.
Larva
Fig. 18, a -f
Diagnosis
Scutum wider than long, the cervical grooves attaining the posterolateral margin; article 1 of palpi enlarged, extending inwards to base of mouthparts and ventrally with posterior margin as in female and nymph, articles 2 and 3 very broad, dentition 2/2; coxae unarmed.
Description
Body.-Unfed larva 0.67 by 0.57 min, partly engorged larva, 1.0 by 0.7 mm, oval, with some minute hairs.
Fig. 18.-I. tasmani, larva: a, capitulum (dorsal view); b, capitulum (ventral view); c. hypostome; d, scutum; e, tarsus I; f, tarsus IV.
Capitulum.-Length about 0.14 mm; basis shape dorsally as in nymph, about 0.15 mm wide; palpal article I enlarged, dorsally extending inwardly to base of mouthparts, the ventral, lateral salience rounded and not as pronounced as in female and nymph, articles 2 and 3 short and broad converging towards apex of mouthparts, 0.08 mm long, widest medianly, the external marlin angulated, article 3 not as long as article 2.
Hypostome rounded apically. abotit 0.08 mm long, dentition 2/2 of about 8 teeth.
Scutum.-Wider than long, 0.21-0.28 mm by 0.34-0.36 mm, and widest about mid-length, glossy, finely granulated; cervical grooves as in female and nymph.
Anal grooves.-Subparallel posteriorly.
Legs.-Coxae unarmed, tarsi 0.13 mm in length, tapering gradually.
Hosts and Distribution
I. tasmani was originally described by Neumann (1899) from females from unknown hosts from Tasmania and St. Piere I., Bass Strait. Nuttall (1916) added Trichosurus vulpecula, Queensland, and Dasyurops maculatus, Schoinobates volans, and Phascolarctos cinereus, Victoria. Ferguson (1925) recorded the species from a "possum", Eidsvold, Qld., and Seddon (1951) mentioned it as occurring on dogs in Tasmania.
Material examined.-QUEENSLAND: Isoodon obesulus, Brisbane, 29.viii.1953, 2 females, 5 nymphs; 1. obesulus, Brisbane, 2.x.1958, 2 males (bred from nymph); larvae bred from female from "bandicoot", Brisbane, October 1958; Hydromys chrysogaster, Brisbane, 23.vii.1959, 11 nymphs, 1 larva; Melomys cervinipes, Springbrook, 15.vi.1959, 3 larvae; Conilurus albiceps, Mt. Tamborine, 31.v.1951, 2 females Phascolarctos cinereus, Wellington Point, 1.ii.1903, 1 female; Trichosurus vulpecula, Ipswich, 1 female, 1 nymph T. vulpecula, Yalungar, July, 1915, 5 females; T. vulpecula, Ipswich, August 1910, 3 females; T. vulpecula, Brisbane, 3 females; Petaurus sp., Mt. Nebo, 23.xi.1956, 1 female; "possum", Gayndah, 1 female; "possum", Murphy's Creek, 12.ix.1950, 1 female; "possum", Emerald, 1 female; "possum", Harrisville, 9.xii.1910, 2 females; "possum", Bundaberg, 3.vii.1906, 1 female; "possum", Roma, 26.ix. 1917, 1 female; Felis catus, Brisbane, 12.ix.1950, 2 females; F. catus, Brisbane, 7.ix.1951, 2 females; Canis familiaris, Brisbane, 8.x.1952, 2 females; Equus caballus, Maryborough, 2.viii.1930, 1 female; F. catus, Brisbane, 1 female; Rattus assimilis, Mt. Glorious, 2 nymphs; R. norvegicus, Mt. Glorious, 2 larvae; "rabbit-rat", Tamborine, July 1948, 2 nymphs; "rat", Brisbane, 7.ix.1950, 2 nymphs, 2 larvae; Uromys sp., Ravenshoe, January 1951, 1 nymph man, Boyne Valley, November 1915, 1 nymph man, Brisbane, 29.iii.1957, 1 female. NEW SOUTH WALES: Pseudocheirus laniginosus, Lismore, 2.ix.1928, 1 female; P. cinereus, Tweed R., August 1902, 1 female; T. vulpecula, Canberra district, 11.v.1957, 8 females, 5 nymphs, 2 larvae; T. vulpecula, Canberra district, 28.x.1958, 1 male, 4 nymphs; T. vulpecula, Yass, 24.i.1934, 2 females, 1 nymph; Antechinus flavipes, 5 larvae; "wombat", Cooma, October 1951, 1 female; C. familiaris, Laura, 1 female; C. familiaris, Towae, 13.iii.1924, 1 female; A. flavipes, 1 male; Woodenbong, 1 female; Bethrungra Hills, 5.x.1938, 1 female; "possum", The Brook, 26.vi.1930, 1female; Moree, 8.iv.1949, 1 female. VICTORIA: F. catus, Markwood, 11.x.1955, 1 female; F. catus, Carrajung, 6.iii.1959, 1 female; P. cinereus, Sassafras, 1 female; "marsupial rat", Tooborac, 6.vii.1928, 1 female, 1 nymph Cape Otway, 24.xi.1949, 1 female Oryctolagus cuniculus, Western District, November 1958, 1 female; man, Gippsland district, 7.iii.1959, 1 female. SOUTH AUSTRALIA: Pseudocheirus sp., Adelaide, 1 female; Protemnodon sp., 1 female; "possum", Bordertown, October 1904, 1 female. WESTERN AUSTRALIA: Hydromys fuliginosus, Swan R., Perth, 4 females. TASMANIA: 2.xii.1928, 1 female Prince Arthur Range, January 1949, 1 female; Sarcophilus harrisii, Hobart, l0.ii.1950, 1 female; "tiger cat", Arthur R., 13.v.1951, 1 female "wombat", Gretna, 24.iii.1960, 3 females.
Comments
The females showed some degree of variation, particularly in the dentition, in the shape of palpal article 1 ventrally, in the shape and punctation of the scutum, and in the shape of the porose areas. The variations in the dentition have already been discussed. Odd specimens have been seen with the scutum somewhat approaching that of I. fecialis in shape and as figured by Neumann (1899), and with the scutal punctations irregularly distributed. The ventral posterior margin of palpal article 1 usually conformed to the figure accompanying the description by the author, but occasional specimens were seen with a much more pronounced notch in this margin. The porose areas were usually oval, but some specimens showed some variation from this shape, which in one female was triangular with a very narrow interval. The variations in the appearance of palpal article 1 ventrally and in the shape and punctation of the scutum and in the sculpturing of the palpi prompted Schulze (1935) to describe two subspecies, namely I. tasmani tasmani and I. tasmani victoriae, but in the present author's opinion, the erection of these subspecies is not warranted.
The description of the male by Nuttall (1916) is very brief and inadequate and was taken from a mounted specimen. The description given in this revision is based on two males bred from nymphs collected from I. obesulus and a male taken on A. flavipes.
Reference
Roberts FHS (1960): A systematic study of the Australian species of the genus Ixodes (Acarina: Ixodidae). Australian Journal of Zoology 8:392-485.
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