Among the many ticks of most concern to people are species of the genus Dermacentor. This genus of about forty identified species is extensively distributed in Africa, Eurasia and the Americas. Examples embody the meadow tick D. reticulatus in Europe, and the wooden tick D. variabilis and Rocky Mountain wooden tick D. andersoni in North America. They’re parasites of mammals, together with each generalist and extra host-specific species; data of Dermacentor people from reptiles and even carpenter bees (Goddard & Bircham 2010) presumably signify incidental and/or unintended associations. Species of Dermacentor are chargeable for the unfold of micro organism inflicting ailments similar to Rocky Mountain noticed fever (which, regardless of sounding like a Nineteen Fifties dance craze, is presumably not a lot enjoyable), Q fever and tularemia. The ticks will also be extra straight hazardous, as their bites inject a toxin that may trigger tick paralysis.
Distinguishing options of Dermacentor species relative to different ticks embody an oblong base to the capitulum, comparatively quick, broad palps, well-developed eyes and the presence of festoons (impressed divisions of the posterior margin of the physique) (Keirans 2009). Most are ornate—that’s, marked on the dorsum with contrasting pale patterns—with the notable exception of the tropical horse tick D. nitens of the Americas (till not too long ago, usually handled as forming its personal genus Anocentor). The operate of such markings is unknown although recommendations embody environmental safety, warning predators of distastefulness, or sexual signalling.
Nearly all of Dermacentor species have a three-host life cycle, dropping off the host between every of the life phases of larva, nymph and grownup, and in search of out a brand new host after moulting. Nevertheless, no less than two New World species, the aforementioned D. nitens and the winter tick D. albipictus (a parasite of deer), are one-host ticks that stay on their authentic host between instars. Typically, Dermacentor species are extra resilient to dry climates than many different tick species. Particular person species can differ of their local weather tolerance, nonetheless. In North America, the geographical divide between D. variabilis within the east of the continent and D. andersoni within the west appears to be pushed by the necessity for the latter of drier situations (Yoder et al. 2007). Older instars additionally are usually hardier than youthful. Females of the ornate sheep tick D. marginatus, a European species, depart their host after gorging firstly of winter after which await extra amoenable spring situations earlier than laying their delicate eggs (Dörr & Gothe 2001).
Greater relationships throughout the genus don’t seem to have been extensively studied. A preliminary molecular phylogeny of onerous ticks has prompt the potential for a basal division between Afrotropical, Eurasian and New World lineages (Barker & Murrell 2004). Comparability with associated tick genera raises the potential for an Afrotropical origin for Dermacentor, although the genus has solely a relictual presence in that continent now. Nevertheless, with solely a handful of species subjected to broad phylogenetic evaluation thus far, additional testing is demanded. Does the continental divide maintain true? Do the one-host species type a single clade throughout the genus? Inquiring minds want to know.
Barker, S. C., & A. Murrell. 2004. Systematics and evolution of ticks with an inventory of legitimate genus and species names. Parasitology 129: S15–S36.
Dörr, B., & R. Gothe. 2001. Chilly-hardiness of Dermacentor marginatus (Acari: Ixodidae). Experimental and Utilized Acarology 25: 151–169.
Goddard, J., & L. Bircham. 2010. Parasitism of the carpenter bee, Xylocopa virginica (L.) (Hymenoptera: Apidae), by larval Dermacentor variabilis (Say) (Acari: Ixodidae). Systematic and Utilized Acarology 15: 195–196.
Keirans, J. E. 2009. Order Ixodida. In: Krantz, G. W., & D. E. Walter (eds) A Guide of Acarology 3rd ed. pp. 111–123. Texas Tech College Press.
Yoder, J. A., D. R. Buchan, N. F. Ferrari & J. L. Tank. 2007. Dehydration tolerance of the Rocky Mountain wooden tick, Dermacentor andersoni Stiles (Acari: Ixodidae), matches desire for a dry surroundings. Worldwide Journal of Acarology 33 (2): 173–180.