Archaeocroton, Barker & Burger, 2018

Barker, Stephen C. & Burger, Thomas D., 2018, Two new genera of hard ticks, Robertsicus n. gen. and Archaeocroton n. gen., and the solution to the mystery of Hoogstraal’s and Kaufman’s “ primitive ” tick from the Carpathian Mountains, Zootaxa 4500 (4), pp. 543-552 : 547-549

Archaeocroton n. gen.

Type species: Amblyomma sphenodonti ( Dumbleton, 1943) (the tuatara tick)

Type depositories: The record of Guglielmone et al. 2014 (p. 498) about the types is apparently correct: CI (holotype), CG (paratype) ( Kaufman 1972 under A. fimbriatum ) as Aponomma sphenodonti . CI, Cawthorn Institute, Nelson, New Zealand; CG, Collection of E.S. Gourlay.

Diagnosis. With characteristics of its sole constituent species, Archaeocroton sphenodonti n. comb. ( Dumbleton, 1943). Dumbleton (1943) has detailed diagnoses of the larvae, nymphs, males and females; these diagnoses will not be repeated here. Ar. sphenodonti n. comb. is the only reptile-tick that is known to be native to NZ; this information together with the detailed diagnoses of Dumbleton (1943) make Ar. sphenodonti n. comb. readily distinguishable from all other ticks.

Etymology. The name of this new genus points to the seemingly archaic (plesiomorphic) nature of the lineage of ticks represented by the tuatara tick ( Burger et al. 2012, 2013). Archaeocroton means old (archaeo, Greek) tick (croton, Greek). The name Archaeocroton is neuter; this should be taken into consideration should other species be added to the genus Archaeocroton n. gen.

New combination. Archaeocroton sphenodonti ( Dumbleton, 1943) for Amblyomma sphenodonti ( Dumbleton, 1943)

Remarks. The vernacular name the "tuatara tick" was apparently first used in the refereed scientific literature by Godfrey et al. (2008) although Ruffell (2005) used this name earlier in his unpublished MSc thesis. We too think that “tuatara tick” is a suitable name for Ar. sphenodonti n. comb. Archaeocroton sphenodonti n. comb. could not be confused with any other tick in New Zealand since the only other hard ticks ( Ixodidae ) known in New Zealand are eight species of Ixodes and one species of Haemaphysalis , H. longicornis Neumann, 1901 ( Heath et al., 2011; Heath & Palma, 2017).

The colour of the gut and other tissues of Ar. sphenodonti n. comb. are remarkable in being purplish ( Fig 4 ; Dumbleton 1943). It is not known whether this purplish colour is due to the blood of its host or something else.

Archaeocroton sphenodonti n. comb. might be as important to the discipline of tick biology as it's host, the tuatara, is to the biology of reptiles since studying relic species, in particular the genomes and transcriptomes of relic species, might reveal much about archaic worlds. The ticks, order Ixodida , have a particularly long history; perhaps even back to the Devonian (406-368 million years ago) ( Dobson & Barker 1999; Barker et al. 2014). Thus, we need all the help we can get to unravel the history of the ticks. The genomes, transcriptomes and proteomes of Ar. sphenodonti n. comb. might contribute to this endeavour. So far only the mitochondrial genome of Ar. sphenodonti n. comb. has been studied ( Burger et al. 2012, 2013) and a handful of nuclear genes ( Dobson & Barker, 1999; and Miller et al. 2007, small subunit (18s) rRNA; Burger et al. 2012, part of the large subunit (28s) rRNA). A deep understanding of modern-day ticks is predicated on an adequate understanding of their history.

There is apparently no conservation management plan for Ar. sphenodonti n. comb. although ticks were apparently successfully translocated with their hosts to six islands in New Zealand in a project aimed at conserving their hosts ( Ruffell 2005 p. 9). One thesis ( Kaufman, 1972) and 12 main papers provide information and insight into this species: Dumbleton (1943), Heath (1977, 2006), Miller et al. (2007), Godfrey et al. (2008, 2010a, 2010b, 2011a, 2011b), Herbert et al. (2010) and Burger et al. (2012, 2013).

Figures

FIGURE 4. Archaeocroton sphenodonti n. comb., horizontal scale bar 1.0 mm; vertical scale bar 2.1 mm.