''Otobius megnini'', also known as the spinose ear tick, is a soft-bodied

tick Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...

that is only parasitic in the

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

l and nymphal stages. As its common name suggests, the spinose ear tick's parasitic forms are usually found within the ears of the

definitive host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' ( symbiont). The guest is typically provided with nourishment and shelter. Examples include ...

. This tick has a worldwide distribution, with common hosts that include horses, cattle, sheep, goats, and dogs.

Importance

Spinose ear ticks are a constant source of annoyance and irritation for their definitive hosts. Their tendency to occur in large numbers can cause

ulcer An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing o ...

ation of the inner ear, high sensitivity of the ears, large amounts of blood loss, and even deafness. Heavily infested animals often shake and rub their heads, which can cause their outer ears to become excoriated and raw. Several cases of human infestation have been reported, and the tick has been incriminated in some instances of

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

transmission.

Anatomy

As with many soft ticks, the mouthparts of ''O. megnini'' are not visible from the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

view. The nymph is somewhat violin shaped with tiny, backward-projecting spines covering the body, which are the reason for the description ''spinose'' in the common name. The adult may achieve in length, is brown, and has a slightly granular body cuticle. The male and female closely resemble each other; neither possesses a scutum.

Habitat

Although spinose ear ticks are generally associated with

semiarid A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi- ...

arid A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ...

environments such as those found in the Southwestern United States, they can also be found in other climate areas due to widespread interstate transportation of animals. Larvae and nymphs usually remain within the ears of their host. Fully grown nymphs and adults live off the host, but still within the host's general environment. They usually prefer dry, protected places such as in cracks and crevices or under logs and fence posts.

Lifecycle

''O. megnini'' has a single-host lifecycle in which the larvae and nymphs remain deep within the external ear canal of their definitive host for long periods of time. The eggs are laid on or near the ground and hatch in 18 days or more. The larvae then crawl up vegetation, fence posts, or the like to wait for a host. They are capable of surviving without a host for more than 2 months. Once the larvae find a host, they migrate to the ears and feed for 5–10 days. They then

molt In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

and become nymphs, still remaining within the host's ear. The nymphs feed for about a month, after which they crawl out of the ear onto the ground to molt again and become adults. The nymphal stages can remain in the ear for 1–7 months, and adults can produce eggs for up to 6 months. Spinose ear tick adults do not feed; they absorb water from the atmosphere to survive.

References

{{Taxonbar, from=Q10613341 Ticks Animals described in 1884 Arachnids of North America Argasidae