2020

The Invertebrate of the Year 2020 - the Ornate Cow Tick

The Latvian Entomological Society has chosen the ornate cow tick (Dermacentor reticulatus), an endoparasitic haematopoietic animal species, as the Invertebrate of the Year 2020. This animal has come from the south and only in the last decades has spread across Latvia. This tick is rapidly “conquering” the territory of our country. The species is more likely to expand its northern distribution range due to climate change.

The ornate cow tick is a relative of the family of ticks that we already know, namely, the castor bean tick (Ixodes ricinus) and the taiga tick (Ixodes persulcatus). The ornate cow tick could be epidemiologically as important, because it also carries agents of zooanthroponosis, including those causing tick-borne encephalitis, Lyme borreliosis, babesiosis, ehrlichiosis.

Spring is approaching. The majority of castor bean ticks and taiga ticks recover completely from winter anabiosis (suspended life) in spring when the ambient temperature stabilizes to at least +5 to + 6 °C. In turn, the ornate cow tick is activated earlier, usually as little as +4 °C is sufficient.

The ornate cow tick is also distinguished among its relatives by its relatively high speed of movement and the fact that it does not avoid flooded areas. Moreover, this species is characterized by greater fertility and a two times shorter development cycle. The development cycle of Dermacentor reticulatus under favourable conditions usually lasts only one year.

Ticks are relatives of spiders

Despite the fact that this year’s invertebrate animal has been chosen by entomologists (insect researchers) and that people most often turn to entomologists for information about ticks, it should be emphasized that ticks are closer relatives to spiders and not to insects. Ticks are not insects!

There are a number of features that distinguish invertebrate ticks from invertebrate insects. They include the number of legs (ticks have four pairs, whereas insects only have three); they do not have wings, no separate head. Ticks, unlike insects, do not have tactile organs - antennas, antennulae.

A person who investigates and studies ticks is called acarologist. There are no such highly specialized tick researchers in Latvia, so entomologists took the responsibility to award the title of the annual invertebrate animal to the ornate cow tick. Their motive was to encourage people to become involved in the study of this animal.

Four stages of development

The development of all ticks involves four stages: 1) an egg, 2) a caterpillar or larva, 3) a nymph, 4) an adult animal or imago. In order to evolve from the larval stage to the next stage, it must eat every time.

Females lay eggs in the soil. In the first stage of life after hatching, or in the larval stage, ornate cow ticks have a hidden lifestyle. The larvae feed mainly on the blood of small objects (mainly of rodents, insectivora, hedgehogs, and hares).

After the “skin” change, in the next stage, the lifestyle of nymphs (animals at this stage are larger than larvae but smaller than adults) is similar to that of larvae.

The most significant change takes place when the nymph once again changes its “skin” to enter the final stage of the developmental cycle - an adult female or male. Males are more ornate than females. The main task of an adult male is to find an adult female that has attached to a victim's circulatory system and fertilize her. The main task of adult females is to find the “blood donor” (protein source) needed for the development of eggs in her body after mating.

Adult ticks feed on large and medium-sized mammals, whether wild or domestic. They suck mainly blood of even-toed ungulates and carnivorans,

Selection of potential victims

When an ornate cow tick is lucky enough to get on a donor's body, it tends to move around a long time in search of a specific site where to suck on. The parasite, of course, tries to find a spot where blood vessels are close to the skin, but it is no less important that the “dining place” has lots of hair. This is good news for people who are afraid of ticks because we do not have much hair. Maybe that is why ornate cow ticks rarely suck on humans. Moreover, once these animals have been searching for a specific site for a long time, they are more likely to be noticed in a timely manner. Ornate cow ticks are larger and more mobile than the other ticks that live in Latvia, and therefore easier to spot.

When ticks are not anabolic or sucked on their victim, they spend their lives waiting for their victim. Ornate cow ticks usually wait for their feed on a stem of an herbaceous plant. They can be sitting at a height of a few centimetres up to seventy centimetres (and up to one metre in wet weather). Ornate cow ticks prefer grassy areas.

Ornate cow ticks inhabit both open areas and deciduous and mixed forests. They like forest edges, fields, overgrowth clearings, shrubs, but are particularly fond of grassland habitats, primarily pastures and meadows.