Ixodes barkeri, Barker, 2019

Barker, Dayana, 2019, Ixodes barkeri n. sp. (Acari: Ixodidae) from the short-beaked echidna, Tachyglossus aculeatus, with a revised key to the male Ixodes of Australia, and list of the subgenera and species of Ixodes known to occur in Australia, Zootaxa 4658 (2), pp. 331-342: 332-337

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Ixodes barkeri

new species

Ixodes barkeri   new species

Material examined. Holotype: male; Peeramon Scrub, Atherton Tableland, Far North Queensland (- 17.32° S, 145.62° E); 750 m altitude; collector, G. B. Monteith ( QM # MS 109845 View Materials ); Barker and Barker reference number B4994; 9 December 1999; collected from vegetation. Deposited in the Queensland Museum ( QM), Brisbane GoogleMaps   . Paratype: male; Far North Queensland (precise latitude and longitude not known but probably in the vicinity of the Atherton Tableland); collector I. Beveridge (reference 10R)); Australian National Insect Collection ( ANIC 48- 005261 View Materials ); Barker and Barker reference number B3421; 15 May 2013; collected from a road-killed short-beaked echidna, T. aculeatus     .

Description: Male. Body: ( Figs 1–4 View FIGURES 1–2 View FIGURES 3-4 ) length 2.20 mm (2.55 mm), width 1.23 mm (1.57 mm) (at level of spiracles). Narrow-oval body-profile (sensu Barker & Walker, 2014 p. 7). Setae short, pale and sparse.

Capitulum: ( Figs 5, 6, 8 View FIGURES 5-9 ) hypostome posterior width 0.36 mm (0.39 mm), dentition 3+3, with a few short setae. Palps short, broad, rounded apically. Palp article 1 wider than long, with a distinctive horn-like projection 0.16 mm long (0.17 mm) ventrally ( Fig. 6, 8 View FIGURES 5-9 ). Palp articles 2 and 3 fused. Carinae absent. Cornua well-developed and bluntly pointed. Scapulae blunt. Porose areas with pits.

Conscutum: ( Figs 2 View FIGURES 1–2 , 4 View FIGURES 3-4 ) length 2.15 mm long (2.50 mm), 1.37 mm wide (1.57 mm), with a few very short fine, pale setae. Lateral grooves deep at periphery of scutum. Punctations large and dense. Cervical grooves short and shallow anteriorly.

Genital aperture: ( Fig. 3 View FIGURES 3-4 ) on a level between coxa II and III.

Spiracular plate: ( Figs 3 View FIGURES 3-4 , 7 View FIGURES 5-9 ) circular shaped (sensu Barker & Walker, 2014 p. 17).

Ventral plates: ( Fig. 3 View FIGURES 3-4 ) jugular plate absent. Pre-genital plate hexagonal, wider than long, length 0.14 mm (0.15 mm), width 0.25 mm (0.28 mm). Median plate hexagonal, longer than wide, length 1.10 mm (1.12 mm), width 0.74 mm (0.90 mm) with dense punctations uniformly distributed. Accessory plate extending from coxa III to IV, with length 0.37 mm (0.40 mm) and width 0.15 mm (0.15 mm). Adanal plates rectangular, length 0.64 mm (0.66 mm), width 0.33 mm (0.35 mm), with punctations uniformly distributed. Anal plate rounded anteriorly, twice as long as wide, length 0.64 mm (0.67 mm), width 0.33 mm (0.37 mm) and open at posterior. All plates evenly punctate with a few short and fine setae.

Legs: ( Figs 1–4 View FIGURES 1–2 View FIGURES 3-4 ) coxae with smooth surfaces without syncoxae, but with faint ridges. Coxae without internal spur. Coxae with external spurs acutely pointed; spurs on coxae I, II and III similar in size; spur on coxa IV about 1/3 rd size of spurs on coxae I, II and III. Ventral surface: trochanters I, II and III with a distinct pointed spur; trochanter I spur about half the size of spurs on trochanters II and III. Trochanter IV with small blunt spur/protuberance. Dorsal surface: trochanter I spur well-developed; trochanter II spur pointed, about half the size of trochanter I spur; trochanter III spur blunt, about half the size of trochanter II spur; trochanter IV protuberance/spur minute. Tarsi I and II steeply stepped, tarsi III and IV gradually stepped. Dorsal humps on tarsi small: tarsus I and II abruptly humped, tarsus III not abruptly humped, tarsus IV not humped (tarsal dorsal humps in the sense of sensu Barker & Walker, 2014 p.18).

Etymology. It is a great pleasure for me to name this species for my husband, Stephen C. Barker, for his contribution to tick systematics, and for passing his passion for ticks, lice and other ectoparasites to me.

Differential diagnosis. Ixodes barkeri   is unlike all the other 21 species of Australian Ixodes   for which males are known, due to the presence of a large ventral horn-like projection on the ventral surface of palp article 1. Ixodes barkeri   is, however, similar to I. zaglossi   of Papua New Guinea, with which it shares this horn-like projection; however, the horn-like projection on palp article 1 of I. zaglossi   ( Fig. 9 View FIGURES 5-9 ) is much shorter and broader than the long, thin, pointed horn-like projection of I. barkeri   ( Fig. 6, 8 View FIGURES 5-9 ). Ixodes barkeri   can also be distinguished from I. zaglossi   by the presence of armed coxae in I. barkeri   : the coxae of I. zaglossi   are unarmed ( Kohls, 1960). Moreover, I. barkeri   does not have syncoxae whereas I. zaglossi   does. The males of two described species of Ixodes   from Papua New Guinea are not known: Ixodes luxuriosus Schulze, 1932   and Ixodes steini Schulze, 1932   . Ixodes barkeri   cannot be either of these species since I. luxuriosus   and I. steini   have coxae that are not armed and syncoxae whereas I. barkeri   has coxae that are armed but no syncoxae ( Schulze, 1935). The male is unknown for five species of Australian Ixodes   . Ixodes barkeri   is unlikely to be the male of any of these because: (i) Ixodes woyliei Ash et al., 2017   has only been found on the woylie, Bettongia penicillata   , and the southern brown bandicoot, Isoodon obesulus fusciventer   , in south-west Western Australia ( Ash et al., 2017); (ii) Ixodes heathi Kwak et al., 2018   has only been found on the mountain pygmy possum, Burramys parvus   , in the Victorian Alps ( Kwak et al., 2018); (iii) Ixodes hydromyidis Swan, 1931   has only been found on the water rat, Hydromys chrysogaster   , the bush rat, Rattus fuscipes   , and the black rat, Rattus rattus   in south-west Western Australia ( Roberts, 1970); (iv) Ixodes ornithorhynchi Lucas, 1846   has only been found on the platypus, Ornithorhynchus anatinus ( Roberts, 1970)   ; and (v) Ixodes vestitus Neumann, 1908   has only been found on the numbat, Myrmecobius fasciatus   , in south-west WA ( Roberts, 1970), and a snake, recorded as the eastern brown snake Pseudonaja textilis (Nuttall & Warburton, 1911)   but now likely to be considered another species of Pseudonaja   .

Remarks. Only one of the two specimens of I. barkeri   was from a short-beaked echidna. However, I speculate that the short-beaked echidna is the host species of I. barkeri   , and moreover that this species of tick might be restricted to Far North Queensland. My reasoning is two-fold. Firstly, ticks have been collected from short-beaked echidna reasonably extensively and intensively in Australia, especially in eastern Australia, although less so in Far North Queensland ( Fig. 10 View FIGURE 10 ). If I. barkeri   was not at least somewhat host-specific and/or was geographically widespread, then I would have expected to find more specimens of I. barkeri   in museum collections. Also, I do not expect I. barkeri   to be present in Papua New Guinea because no Ixodes   species were reported by Hoogstraal (1982) from the short-beaked echidna, T. aculeatus   , in Papua New Guinea, but this is certainly possible. Secondly, the possible sister-species of I. barkeri   is I. zaglossi   , a species of tick that has been found only on the long-beaked echidna, Zaglossus bruijnii   , albeit in Papua New Guinea not Far North Queensland. Zaglossus bruijnii   is found in rainforests ( Flannery, 1995 p. 71); one of my two specimens was found in a rainforest, the Peeramon Scrub, Atherton Tableland, Far North Queensland. Perhaps I. barkeri   shares with I. zaglossi   a most-recent-common-ancestor ( MRCA) that once inhabited the rainforests of the Sahul, the combined land masses of Australia, Papua New Guinea and neighbouring islands.

Brief overview of Australian Ixodes   . Australian species of Ixodes   are largely known from their morphology alone, but the taxonomy of Roberts (1970) remains robust; the one in-depth study of the genetics of closely related species of Ixodes   of Australia ( Song et al., 2011) confirmed the value of morphology as a basis for conceiving species of Australian Ixodes   . Taxonomic works by authors after Roberts (1970) have continued the high standard of Roberts and thus Australian species of Ixodes   are readily identified from morphology alone e.g. Heath & Palma (2017). Most species are easily placed in a subgenus, but some, including I. barkeri   cannot be easily placed in a subgenus.


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