How does forest ticks reproduce?

Ixodid ticks (family Ixodidae) are a small group of arachnids. This family is one of the most studied, since it includes the largest parasite mites of humans and domestic animals. The family worldwide includes more than 600 species, and about 60 are noted in modern Russia.

All ixodid ticks are temporary parasites.. They are called temporary because they are on the host's body not throughout life, but only during feeding (blood feeding is critical for the reproduction process of these ticks, since additional nutrition is not typical for them).

The increased interest in this family is primarily due to the fact that its representatives carry dangerous diseases such as encephalitis, typhus, and tularemia. From the point of view of epidemiology, the most interesting are the taiga tick (lat. Ixodes persulcatus) and the dog tick (lat. Ixodes ricinus), which are widespread in Russia and are carriers of tick-borne encephalitis.

We will talk further about how the reproduction of these ticks occurs ....

 

Mass reproduction and distribution of ticks

Despite the fact that dog and taiga ticks are quite common in our territory, they can be found far from everywhere. They live in deciduous and coniferous forests with lush grassy and shrubby vegetation. Moreover, the hotter the region, the more humid areas ticks prefer, and vice versa.

The characteristic habitats of ticks are moist forest edges, well-lit by the sun, paths and lawns of parks, and vegetation near water bodies. If the tick finds favorable conditions for its living, it begins to actively multiply.

For ticks, active population outbreaks are described, when a large number of adults and their larvae are concentrated in a small, favorable area. It is not necessary to explain that when a person enters such biotopes, contact with ticks is almost inevitable.

Centers of mass reproduction of ticks in the north of Russia also appear at the borders of different natural habitats (rough terrain), when deforestation is done, parasites move to pastures, where they actively feed on farm animals. In nature, the reproduction of ticks is constrained by the low density of prey, while on pastures there are more than enough hosts.

The phenomenon of mass reproduction is also dangerous because when the population reaches a certain density, there is a mass settlement of parasites in neighboring territories, where outbreaks also occur over time. If such a population includes ticks carrying a disease, such as encephalitis, then the disease migrates farther and farther along with its “hosts”. This can lead to high morbidity among people and even an epidemic.

It is possible to identify places with a significant probability of such an outbreak, but it is extremely difficult to predict it, because many factors affect the reproduction of ticks (see below), including weather conditions, which vary greatly in different years.

 

Life cycle features

The life cycle is understood as the entire period of development and life of the organism - in this case, from an egg to an adult sexually mature individual. The life cycle of encephalitic ticks is quite complex, characterized by a change of hosts and lasts more than 1 year. It consists of an egg, a larva, a nymph and an adult (adult).

We begin the description of the life and reproduction of ticks from the meeting of the sexes. Male and female are usually found in nature, much less often on the host organism. The latter is less typical, since the chances of parasitizing 2 mites per 1 organism are relatively small.

After the male finds the female, fertilization occurs. An interesting mechanism for the transfer of seed material. Copulation or intercourse does not occur. The male leaves a kind of sac with spermatozoa (spermatophore) on the substrate, which protects the sperm from the action of external factors. The female crawls up to the capsule and grabs it with special flaps located near the genital opening, like with tweezers. This is how fertilization occurs.

On a note

Male and female ixodid ticks are easy to distinguish from each other even to the layman. If you look at the tick from above, you can see that its body is covered with a shiny dense chitinous shield that performs a protective function. In males, this shield covers the entire back, and the body cannot stretch much when feeding. In females, the shield is smaller and covers only half of the back, because of which her body can increase in size several times.

After fertilization, the females begin to actively seek prey for food. Ticks are characterized by the so-called "gonotrophic harmony", when the process of nutrition is closely connected with the maturation of eggs. In simple terms, almost all the nutrients extracted from the blood will go to the development of eggs.

Accordingly, each oviposition is necessarily preceded by bloodsucking. Because of this, females are very voracious - their abundant food is the key to successful reproduction. Males eat less often and in much smaller quantities. In some species of ticks, males do not feed at all, and after the transfer of seed material they die.

It is interesting

In some species of Ixodes, males do not look for prey on their own. During the sexual process, they pierce the integument of the female and feed on the contents of her intestines, without causing significant damage to her. It also has little effect on oviposition.

Females are sucked with blood for a long time, on average, about 10 days. Soft integuments allow the consumption of large volumes of blood. Sometimes 20 minutes is enough to feed the males.

The female tick begins to lay eggs a week or a month after she has finished feeding (the rate of egg maturation depends on external factors). Laying lasts about a month, with the tick laying eggs in small groups as it matures.

Ticks are very prolific - up to 2000 eggs can be found in their clutches. The number of eggs depends on how well-fed the female was, and the anxiety factor also plays an important role. For female ticks, additional food is also characteristic, when the first was not enough. Sometimes mites are supplemented directly during the period of oviposition, which, of course, makes it longer.

The clutches are located either on the soil in the natural environment, or (much less often) on the body of the host, which increases the chances of future larvae feeding.

Within a month after laying, the eggs hatch into larvae. They are small, outwardly similar to adult ticks, but there are a number of differences. The larvae have 3 pairs of walking legs (like insects) and do not have a genital opening.

For some time after leaving the egg, the larvae sit on the clutch, waiting for their outer covers to harden. Then they crawl in search of prey.

Aggregation of larvae on clutches is known even after hardening of the covers - hungry individuals do not disperse, but wait for a future victim on the surface of plants or soil. Then not one larva is attached to the host, but several at once. This weakens the immune response of the victim's body and contributes to better saturation of the larvae.

The larvae feed for 2-4 days, after which they detach from the host, or stay on it for some time, using it as a shelter. Then they again fall into the natural environment, where they molt into nymphs.

Tick ​​nymphs are similar to adults (adults), have 4 pairs of walking legs, an oval body with dense covers, but there is no genital opening yet.

Molting in the life cycle of these parasites can be considered a kind of diapause, during which ticks do not feed and do not move, complex biochemical processes occur in their bodies. Even after ixodids molt, they are not capable of active life for some time, because changes in the body continue.

Moulting is necessary for all arthropods, since the dense chitinous external skeleton hinders growth and development.It is during this short period of time, while the old covers come off, and the new ones have not yet hardened, that the body grows. The rest of the time is spent preparing for this process.

The phased type of development eventually makes it possible to start feeding on larger prey and occupy other ecological niches - this is an important evolutionary mechanism that allows reducing trophic and stationary intraspecific competition, which means increasing the population's chances for active reproduction.

Adults do not grow, their appearance remains unchanged.

It is interesting

The shapes and sizes of the body of imago ticks, like insects, are unchanged and are a species trait by which the organism can be identified. A good example is ladybugs, where the body size and the number of points on which remain constant and serve to identify the species.

Nymphs feed on the host for about a week, after which they leave it. After some time, they either go to winter, or turn into adults. Larvae, nymphs and adults can hibernate.

Cases of hibernation of ticks in the ears and other parts of the body of ungulates are known. But more often, ixodid ticks overwinter in their natural habitats: under plant dendrites, in soil, under stones and old wood, under the bark of dry trees, in mammalian burrows and bird nests. Sometimes ticks remain in cattle yards, in outbuildings, where they are brought by domestic animals.

In general, diapause in ixodid ticks is not obligate, that is, it is not mandatory. At sufficiently high temperatures, mites may not fall into a dormant state and continue their development indoors during the winter.

Most ixodid ticks have a three-year life cycle. The general scheme looks something like this:

• adults in spring (April-May) actively attack vertebrates. This period is characterized by the greatest dynamics of the taiga and dog ticks, so you need to be especially careful when walking in nature. In late summer, as a rule, adults do not feed on animals. The larvae appear in the second half of summer. Regardless of whether they are satiated or not, wintering takes place;
• During the entire second year, the larvae develop and molt into nymphs. Hungry and full nymphs leave for the winter;
• In the third year, the nymphs actively feed, and at the end of summer they turn into adults. In autumn, adults do not look for victims and immediately fall into diapause.

Now it becomes clear why the danger of contact with ticks increases in the spring. In areas with dry hot weather, the cycle can take place quite quickly, in 1-2 years - then the dynamics are high not only in spring, but also in autumn.

In laboratory conditions, studies have been repeatedly conducted on the duration of reproduction of ixodid ticks in general. The result was data that varied over a wide range: from 200 to 2000 days (the rate of reproduction in nature corresponds to the middle of this range).

Thus, the life cycle of ticks is characterized not only by longevity, diapauses, and molts, but also by the change of hosts, as well as the alternation of parasitism with a free-living lifestyle. We will just talk about the diversity of the hosts further.

 

Animals on which forest mites breed

Dog and taiga ticks use a wide range of hosts. Moreover, both warm-blooded and cold-blooded animals can become victims. These are large domestic and wild artiodactyls, horses, sheep, wild boars. Smaller animals: dogs, cats, badgers, hares and others.

The photo below shows an example of the parasitism of a large number of ticks on the body of an elk:

The greatest spectrum of parasitism is observed on small mouse-like rodents, including in their burrows: dormice, voles, forest mice. Such insectivores as a hedgehog and a mole, ticks also did not deprive of their attention. Among reptiles, parasitism has been observed on lizards and snakes. The favorite prey of the nymphs are birds leading a sedentary lifestyle.

The development of encephalitis mites proceeds according to the three-host type. This means that during the entire life cycle, the tick feeds on three different, systematically, animals.

The larvae choose a smaller host. Massively they can be found on mice, squirrels, hedgehogs. The larvae also feed on reptiles, and sometimes amphibians, which the nymphs already avoid. Nymphs choose a larger host - for example, a dog, a cat, various birds. The taiga tick prefers young hazel grouse.

On a note

Nymphs in ticks also perform a dispersal function. To do this, they use various animals. Clinging to their fur, ticks can move long distances. They also migrate with flying birds, so nymphs can find themselves in habitats that are unusual for them. This phenomenon is called zoochory.

 

Factors that affect the reproduction of ticks

The rate of reproduction of ticks is strongly influenced by external factors.

Here are the most important ones:

• Temperature. One of the most important factors that affects the intensity of reproduction of ticks is temperature. Ticks are quite cold-resistant, and many of them live in northern latitudes, but severe frost during wintering is especially dangerous for them.The older the tick, the more resistant it is to low temperatures. At -10°C, larvae, nymphs and adults survive for more than 7 days, but this is far from the limit. With more severe frosts, behavioral defense mechanisms are activated - ticks hide under the snow, in shelters, burrows, outbuildings, barnyards. The action of high temperatures also has a negative effect on ticks - when overheated, metabolic processes are disturbed, activity and the desire for food decrease. It should be borne in mind that the temperature on the surface of the host's body is usually higher than in the natural environment. The temperature maximum does not exceed +50°С;
• Humidity - plays a very important regulatory role in the development and reproduction of mites. Ticks avoid direct sunlight precisely because of the danger of moisture loss from the body. All arthropods, despite dense chitinous covers, very quickly lose water from the body. Such a strong external skeleton does not protect them from dehydration. The lipid (wax) layer prevents excessive moisture loss. The hotter and drier the climate in which this or that group lives, the more developed this layer is. The soft covers of ixodid ticks pass water very quickly, which greatly affects the state of their body and, accordingly, further reproduction. In dry years, the number of ticks is sharply reduced, while years with heavy rainfall are characterized by outbreaks of mass reproduction;
• anthropogenic factor. People, disturbing the natural habitats of ticks, change food chains and destroy habitual habitats. Ticks have to migrate and adapt to new conditions;
• Food. Well-fed individuals hibernate more successfully, lay more eggs.Larvae that do not need food quickly molt into nymphs, and nymphs into adults. Fertility directly depends on how favorable conditions are in the specified year in the specified territory.

The photo below shows a blood-drinking female tick:

On a note

There is an opinion that the burning of vegetation in typical places of reproduction and development of ticks can significantly reduce their numbers, but this is not entirely true (the effect is usually only temporary). But the damage caused to the biocenosis as a whole will be significant. Treatment of such areas with acaricides also does not always give the desired result.

 

Can ticks develop on dogs and other pets?

As noted above, ticks often use pets as an object of food. Dogs are no exception - probably, many of you have come across ticks on the neck or ears of a dog after a walk.

What to do if you did not notice the tick in time, and the dog brought it into the apartment? Will the parasite be able to breed directly on the dog indoors?

So, the nymph or imago will be on your pet only during feeding, after which they will disappear. It will be difficult not to notice the parasite. Some danger is that eggs may be laid on the dog. But this problem is also easy to solve if your pet is properly cared for - regular inspection of the characteristic attachment points (nape, ears, eyes) will save you from unnecessary consequences.

If you see a tick on your pet, don't panic. It is necessary to carefully remove the body of the parasite with tweezers, without pressing on it, and then treat the wound. At the end of the procedure, wash your hands thoroughly with soap.If you are afraid to remove the parasite yourself, take your pet to the veterinarian.

For several days after removing the tick, observe the dog for redness and abscesses near the attachment site. But usually dogs tolerate such parasitism painlessly, and there will be no significant harm to your pet's health.

 

Reproduction of ticks in an apartment: probability, risks, prevention

Passage of a full life cycle by a tick within one apartment is extremely unlikely, almost impossible. These representatives of arachnids encounter humans and domestic animals only when they need food and while searching for suitable places for wintering. They prefer to lay eggs and molt in natural conditions.

Let's still imagine a possible variant of the flow of such a life cycle in an apartment.

So, the imago of the tick, together with you or your pets, enters the apartment. Also, a tick can appear on its own in the house, for example, from a nearby lawn in the spring, through an open door.

In order to lay eggs, the female needs to be fully fed. After that, the eggs will be able to develop normally if the humidity is high enough. Then difficulties begin - larvae will come out of the eggs, which again need food. Having fed, the ticks need to leave for the winter, and then everything should be repeated with the nymph until it turns into an imago.

It follows from this that, unlike fleas and bed bugs, which develop perfectly in residential premises, ticks, having a complex three-year cycle with a change of owners, are deprived of the possibility of developing in a limited space of an apartment or a private house.

So the most likely and dangerous contact with ticks in natural conditions, during their mass reproduction.

 

In conclusion, we note that such a difficult method of reproduction affects the state of ixodid tick populations as a whole. Constant changes of stations and hosts lead to high mortality among eggs, larvae and nymphs. However, in nature, everything is compensated. Like all parasites, mites are very prolific, and a sufficient number of juveniles survive to adults to maintain the population at the proper level.

 

Interesting video: how ticks lay eggs after being bitten

 

Life cycle of development of ixodid ticks