The Ixodidae are the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of hard ticks or scale ticks, one of the three families of

tick Ticks are parasitic arachnids of the order Ixodida. They are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, and species, but can become larger when engorged. Ticks a ...

s, consisting of 771 species, . They are known as 'hard ticks' because they have a scutum or hard shield, which the other major family of ticks, the 'soft ticks' (

Argasidae The Argasidae are the family of soft ticks, one of the three families of ticks. The family contains 193 species, although the composition of the genera is less certain, and more study is needed before the genera can become stable. The currently a ...

), lack. They are

ectoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...

of a wide range of host species, and some are

vector Vector most often refers to: * Euclidean vector, a quantity with a magnitude and a direction * Disease vector, an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematics a ...

s of pathogens that can cause human

disease A disease is a particular abnormal condition that adversely affects the structure or function (biology), function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical condi ...

Description

They are distinguished from the Argasidae by the presence of a scutum. In both the

nymph A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

and the adult, a prominent

gnathosoma The gnathosoma (from Greek , ' = "jaw" and , ' = "body") is the part of the body of the Acari (mites and ticks) comprising the mouth and feeding parts. These are the hypostome, the chelicerae and the pedipalps. It is also called the capitulum (how ...

(or capitulum,

mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...

and feeding parts) projects forward from the animal's body; in the Argasidae, conversely, the gnathosoma is concealed beneath the body. They differ, too, in their lifecycle; Ixodidae that attach to a host bite painlessly and are generally unnoticed, and they remain in place until they engorge and are ready to change their skin; this process may take days or weeks. Some species drop off the host to

moult In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at ...

in a safe place, whereas others remain on the same host and only drop off once they are ready to lay their eggs.

Classification

As of late 2009, there were considered to be 702 extant species in 14 genera, according to ''Robbing et al.'' using the 2002 classification of Barker and Murrell. The family contains these genera: * '' Africaniella'' – 2 species * ''

Amblyomma ''Amblyomma'' is a genus of hard ticks. Some are disease vectors, for example the Rocky Mountain spotted fever in United States or ehrlichiosis in Brazil. This genus is the third largest in the family Ixodidae, with its species primarily ...

'' – 130 species (includes 17 formerly in ''Aponomma'', some still consider a valid genus) * '' Anomalohimalaya'' – 3 species * '' Archaeocroton'' – 1 species * ''

Bothriocroton ''Bothriocroton'' is a genus of hard ticks. There are seven extant member species, native to Australia and Papua New Guinea. ''Bothriocroton'' species typically parasitise monotremes, marsupials, and reptiles. ''Bothriocroton'' ticks have a limi ...

'' – 7 species (all formerly in ''Aponomma'') * '' Cosmiomma'' – 1 species * '' Cornupalpatum'' – 1 species * '' Compluriscutula'' – 1 species * ''

Dermacentor ''Dermacentor'' is a genus of ticks in the family Ixodidae, the hard ticks. The genus has a cosmopolitan distribution, with native species on all continents except Australia. Most are found in North America. Hosts of ''Dermacentor'' ticks inclu ...

'' – 34 species (includes the monospecific former/disputed genus''Anocentor'') * '' Haemaphysalis'' – 166 species * '' Hyalomma'' – 27 species * ''

Ixodes ''Ixodes'' is a genus of hard-bodied ticks (family Ixodidae). It includes important disease vectors of animals and humans ( tick-borne disease), and some species (notably '' Ixodes holocyclus'') inject toxins that can cause paralysis. Som ...

'' – 246 species * '' Margaropus'' – 3 species * '' Nosomma'' – 2 species * '' Rhipicentor'' – 2 species * '' Rhipicephalus'' – 82 species (includes all 5 from the disputed/former ''Boophilus'') * '' Robertsicus'' – 1 species

Fossil genera

* †'' Compluriscutula'' Poinar and Buckley 2008

Burmese amber Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. Th ...

, Myanmar,

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

* †'' Cornupalpatum'' Poinar and Brown 2003 Burmese amber, Myanmar, Cenomanian

Medical importance

Many hard ticks are of considerable medical importance, acting as vectors of diseases caused by bacteria, protozoa, and viruses, such as ''

Rickettsia ''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The genus was n ...

'' and ''

Borrelia ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and are ...

''. Other tick-borne diseases include

Lyme disease Lyme disease, also known as Lyme borreliosis, is a tick-borne disease caused by species of ''Borrelia'' bacteria, Disease vector, transmitted by blood-feeding ticks in the genus ''Ixodes''. It is the most common disease spread by ticks in th ...

babesiosis Babesiosis or piroplasmosis is a malaria-like parasitic disease caused by infection with a eukaryotic parasite in the order Piroplasmida, typically a ''Babesia'' or '' Theileria'', in the phylum Apicomplexa. Human babesiosis transmission via ...

, ehrlichiosis,

Rocky Mountain spotted fever Rocky Mountain spotted fever (RMSF) is a bacterial disease spread by ticks. It typically begins with a fever and headache, which is followed a few days later with the development of a rash. The rash is generally Petechial rash, made up of small s ...

anaplasmosis Anaplasmosis is a tick-borne disease affecting ruminants, dogs, and horses, and is caused by ''Anaplasma'' bacteria. Anaplasmosis is an infectious but not contagious disease. Anaplasmosis can be transmitted through mechanical and biological vector ...

Southern tick-associated rash illness Southern tick-associated rash illness (STARI) is a tick-borne disease resembling a mild form of Lyme disease, which occurs in southeastern and south-central United States. It is spread by bites from the lone star tick ''Amblyomma americanum''. T ...

tick-borne relapsing fever Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus '' Borrelia'', which is transmitted through the bites of lice, soft-bodied ticks (genus ''Ornithodoros''), or hard-bodied ticks (Genus Ixodes). S ...

tularemia Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium '' Francisella tularensis''. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat ...

Colorado tick fever Colorado tick fever (CTF) is a viral infection transmitted from the bite of an infected Rocky Mountain wood tick ('' Dermacentor andersoni''). It should not be confused with the bacterial tick-borne infection, Rocky Mountain spotted fever. Colorad ...

, Powassan encephalitis, and

Q fever Q fever or query fever is a disease caused by infection with ''Coxiella burnetii'', a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including ...

References

External links