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

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 ); Barker and Barker reference number B4994; 9 December 1999; collected from vegetation. Deposited in the Queensland Museum ( QM), Brisbane . 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 ); 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 ) 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 ) 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 ). Palp articles 2 and 3 fused. Carinae absent. Cornua well-developed and bluntly pointed. Scapulae blunt. Porose areas with pits.

Conscutum: ( Figs 2 , 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 ) on a level between coxa II and III.

Spiracular plate: ( Figs 3 , 7 ) circular shaped (sensu Barker & Walker, 2014 p. 17).

Ventral plates: ( Fig. 3 ) 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 ) 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 ) is much shorter and broader than the long, thin, pointed horn-like projection of I. barkeri ( Fig. 6, 8 ). 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 ). 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.

Figures

FIGURE 10. Geographic distribution of ticks from short-beaked echidnas, Tachyglossus aculeatus. Records of Ixodes barkeri are in red, other species of ticks (Bothriocroton concolor, B. tachyglossi, Amblyomma australiense, A. echidnae and A. moyi) are in blue. (Google Maps).

FIGURES 1–2. Ixodes barkeri, male, holotype. 1. Ventral habitus; 2. Dorsal habitus. Scale bar 1.0 mm. Two of the legs of this specimen had broken off the body of the tick so images of the legs from the other side of the tick were pasted onto this image.

FIGURES 3-4. Ixodes barkeri, male, holotype. 3. Ventral habitus; 4. Dorsal habitus. Scale bar 1.0 mm.

FIGURES 5-9. Ixodes spp., males. 5. Ixodes barkeri, capitulum, dorsal view; 6. Ixodes barkeri, capitulum, ventral view; 7. Ixodes barkeri, spiracular plate; 8. Ixodes barkeri, capitulum, ventral view; 9. Ixodes zaglossi, capitulum, ventral view. Arrows indicate the horn-like projection on palpal article 1.