Rhipicephalus

Engorged female brown dog tick Rhipicephalus sanguineus, copyright Felipe Mateo and Cristina.

Belongs within: Ixodida.

Rhipicephalus, the brown ticks, is a genus of ticks that are primarily parasitic on mammals. They are most diverse in Africa though the brown dog tick R. sanguineus is perhaps the world’s most widespread tick. Molecular analysis indicates that the cattle ticks of the subgenus Boophilus should also be classified within Rhipicephalus (Keirans 2009).

Brown ticks
Published 6 February 2012
Brown dog tick Rhipicephalus sanguineus, from here.

Rhipicephalus species are generally referred to as ‘brown ticks’ as, for the most part, they lack any prominent spots or other markings. Rhipicephalus species are found worldwide, though the highest diversity is in Africa, home to about three-quarters of the known species (Walker et al. 2000). They are mostly parasites of mammals, but individual species may be found on a range of host species. A few species are economically significant as vectors of such pathogenic organisms as rickettsias and various Sporozoa, notably the brown dog tick R. sanguineus and the cattle tick R. microplus. The former species has been estimated to cause about US$168 million of losses per year in Africa, while the latter costs Australia about US$100 million a year (Murrell & Barker 2003). A brief drive north of Perth is enough for me to see the impact of the cattle tick on Australian agriculture: as one passes the southernmost limit of the tick’s range, there is a noticeable shift between the Europe-derived cattle breeds (such as shorthorns and Herefords) kept in the south of the country, and the tick-resistant India-derived breeds (such as Brahmans) kept in the north.

Cattle ticks Rhipicephalus microplus on a host, from here.

Distinguishing features of Rhipicephalus from other tick genera include the presence of adanal shields in the males, and a short hypostome and palps. Until recently, R. microplus and four other species were separated into their own genus, Boophilus, but a number of analyses, particularly molecular ones, have indicated that Boophilus is nested within Rhipicephalus (e.g. Beati & Keirans 2001) and the genera were synonymised by Murrell & Barker (2003). Members of the now-subgenus Boophilus differ from the remaining Rhipicephalus species in lacking festoons, a series of crimped grooves running around the posterior body margin (visible in the photo at the top of this post). They are also one-host parasites (that is, they remain on a single host through their lifespan and do not leave the host when moulting) while most other Rhipicephalus (such as R. sanguineus) are three-host ticks (they leave their host when moulting and then find a new host). However, close relatives of Boophilus in the subgenus Digineus are two-host ticks, only changing host when moulting from nymph to adult (Murrell & Barker 2003). However, it is worth noting that none of the analyses that led to the subsuming of Boophilus within Rhipicephalus included any representatives of the genus Margaropus, similar to Rhipicephalus but distinguished by possessing broad heavily-segmented legs. A close relationship between Boophilus and Margaropus was indicated by the morphological analysis of Klompen et al. (1997). If Boophilus is nested within Rhipicephalus, it seems quite possible that Margaropus is as well.

Systematics of Rhipicephalus
<==Rhipicephalus Koch 1844H98
    |--R. (Rhipicephalus) sanguineus (Latreille 1806)K09, H98 [=Ixodes sanguineusH98, R. sanguinius (l. c.)H98]
    `--R. (Boophilus Curtice 1891)K09, H98
         |--R. (B.) annulatusK09
         |--‘Boophilus’ calcaratusKK91
         |--‘Boophilus’ decoloratus (Koch 1844)ADG91
         |--‘Boophilus’ geigyi Aeschlimann & Morel 1965ADG91
         `--R. (B.) microplus (Canestrini 1887)K09, H98 (see below for synonymy)
Rhipicephalus incertae sedis:
  R. appendiculatus (Neumann 1901)ADG91
  R. bursa Canestrini & Fanzago 1877GE02
  R. evertsi (Neumann 1897)ADG91
  R. haemaphysaloidesLC96
  R. pravus (Dönitz 1910)ADG91
  R. pulchellus (Gerstacker 1873)ADG91
  R. pumilioB99
  R. rossicusKK91
  R. sengalensis (Koch 1844)ADG91
  R. simpsoni (Nuttall 1910)ADG91
  R. simus Koch 1844ADG91
  R. turanicusKK91

Rhipicephalus (Boophilus) microplus (Canestrini 1887)K09, H98 [=Haemaphysalis microplaH98, Boophilus annulatus microplusH98; incl. Rhipicephalus australis Fuller 1899H98, B. annulatus australisH98, R. annulatus var. australisH98, Ixodes bovis Riley 1896H98, Boophilus bovisH98]

*Type species of generic name indicated

References

[ADG91] Amoo, A. O. J., O. O. Dipeolu & L. N. Gichuru. 1991. Tick ecology: on-host population dynamics of ticks in the Coast Province of Kenya. In: Dusbábek, F., & V. Bukva (eds) Modern Acarology: Proceedings of the VIII International Congress of Acarology, held in České Budĕjovice, Czechoslovakia, 6–11 August 1990 vol. 2 pp. 461–468. SPB Academic Publishing: The Hague.

Beati, L., & J. E. Keirans. 2001. Analysis of the systematic relationships among ticks of the genera Rhipicephalus and Boophilus (Acari: Ixodidae) based on mitochondrial 12S ribosomal DNA gene sequences and morphological characters. Journal of Parasitology 87 (1): 32–48.

[B99] Belozerov, V. N. 1999. Dormancy in the life cycle of ixodid ticks and their adaptations to predictable and unpredictable environmental changes. In: Needham, G. R., R. Mitchell, D. J. Horn & W. C. Welbourn (eds) Acarology IX vol. 2. Symposia pp. 53–56. Ohio Biological Survey: Columbus (Ohio).

[GE02] Giribet, G., G. D. Edgecombe, W. C. Wheeler & C. Babbitt. 2002. Phylogeny and systematic position of Opiliones: a combined analysis of chelicerate relationships using morphological and molecular data. Cladistics 18: 5–70.

[H98] Halliday, R. B. 1998. Mites of Australia: A checklist and bibliography. CSIRO Publishing: Collingwood.

[KK91] Kamarinchev, B., T. Kovacheva, T. Christova, G. Georgieva & V. Zlatanova. 1991. Studies on mosquitoes and ticks as carriers of alpha-, flavi- and bunyaviruses. In: Dusbábek, F., & V. Bukva (eds) Modern Acarology: Proceedings of the VIII International Congress of Acarology, held in České Budĕjovice, Czechoslovakia, 6–11 August 1990 vol. 2 pp. 89–92. SPB Academic Publishing: The Hague.

[K09] Keirans, J. E. 2009. Order Ixodida. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 111–123. Texas Tech University Press.

Klompen, J. S. H., J. H. Oliver Jr, J. E. Keirans & P. J. Homsher. 1997. A re-evaluation of relationships in the Metastriata (Acari: Parasitiformes: Ixodidae). Systematic Parasitology 38: 1–24.

[LC96] Li, D., & Q. Chen. 1996. Studies on piroplasmoses and the tick (Ixodidae) vectors in China. In: Mitchell, R., D. J. Horn, G. R. Needham & W. C. Welbourn (eds) Acarology IX vol. 1. Proceedings pp. 469–471. Ohio Biological Survey: Columbus (Ohio).

Murrell, A., & S. C. Barker. 2003. Synonymy of Boophilus Curtice, 1891 with Rhipicephalus Koch, 1844 (Acari: Ixodidae). Systematic Parasitology 56: 169–172.

Walker, J. B., J. E. Keirans & I. G. Horak. 2000. The Genus Rhipicephalus (Acari, Ixodidae): a guide to the brown ticks of the world. Cambridge University Press.

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