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

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 ...

that is only parasitic in the

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

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 sloughin ...

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 (, "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 theory of d ...

transmission Transmission or transmit may refer to: Science and technology * Power transmission ** Electric power transmission ** Transmission (mechanical device), technology that allows controlled application of power *** Automatic transmission *** Manual tra ...

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 The fus ...

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 A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

. The male and female closely resemble each other; neither possesses a

scutum The ''scutum'' (; :''scuta'') was a type of shield used among Italic peoples in antiquity, most notably by the army of ancient Rome starting about the fourth century BC. The Romans adopted it when they switched from the military formation of ...

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 sem ...

arid Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...

environments such as those found in the

Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural list of regions of the United States, region of the United States that includes Arizona and New Mexico, along with adjacen ...

, 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 a process by which an animal casts off parts of its body to serve some beneficial purpose, either at ...

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