AW Arachnid Book: Ticks (Ixodida) - Photos & Descriptions
Posted: Sat Dec 07, 2013 3:45 pm
Africa Wild Arachnid Book: Ixodida (Ticks)
Upload your picture of a tick and add a description underneath. Please only do one species per post. All entries will be edited and updated (additional photos and information will be added by moderators). New entries will be posted according to taxonomic order and the post date does not reflect the actual date of new posts.
Ticks are small arachnids in the order Ixodida. Along with mites, they constitute the subclass Acarina. Ticks are ectoparasites (external parasites), living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians.
Morphology of ticks
Ticks are closely related in general body structure to parasitic mites. The separationof ticks from mites is based on two useful morphologic characteristics: firstly the occurrence of a hypostome (ventral mouthpart) that has been modified into a piercing organ (usually with recurved teeth) and secondly the presence of a distinct sensory apparatus (Haller’s organ) on the dorsal aspect of the tarsus of the first leg.
The conscutum covers nearly the entire dorsal surface of male ixodid ticks and so limits the amount of blood that can be ingested. Female ticks and larvae and nymphs also have a scutum, but it covers only the anterior third of the dorsum, thus allowing the tick to expand when engorging.
Life cycle of ticks
There are four stages in the life cycle of an ixodid tick, namely the egg, the larva, the nymph, and the adult. The three instars (larva, nymph and
adult) climb on to the vegetation in order to attach to a passing host or quest for a host from the soil surface. Once on the host, the tick crawls to a predilected feeding site where it cuts the skin with its chelicerae and inserts its hypostome that together with cement secreted by the salivary glands, anchors the tick firmly in place. The tick remains in place for several days (larva, 3–6 days; nymph, 4–7 days; adult female, 7–9 days) during which time active growth of gut and cuticle occurs in order to accommodate the blood meal, most of which will be acquired in the final 24 hours of engorgement. During feeding the blood meal is concentrated by the extraction of water, which is then secreted back into the host by specialised salivary gland cells and is an important means by which tick-borne pathogens invade their hosts. Once fully engorged the tick withdraws its hypostome and falls to the ground where it begins digesting the blood meal and developing to the next instar.
Digestion is slow, and development of the new instars takes several months in temperate regions. The newly moulted (or hatched) unfed tick may remain quiescent for a time, but will eventually ascend the vegetation to quest for a host and a blood meal. After the engorged female detaches from a host digestion of the blood meal and oogenesis take place followed by oviposition. The incubation period of the eggs varies with the species and ambient temperature. Embryogenesis usually lasts 20 – 50 days.
Ixodid ticks have substantial capability to swallow and concentrate a large volume of host blood, their rapid metabolism and body development can explain the on-host intervals. During off-host periods, ticks experience some environmental distress such as climate and temperature. High temperatures and body-water homeostasis are of importance in processes that influence off-host survival. Ticks as a group have this capability to survive without food and/or water longer than most other arthropods. Ixodid species usually spend an annual total of 12-21 days on the host
compared to the off-host period.
Off-host fasting is characterized by slow metabolism with lengthy intervals of immobility, interrupted by movement within the microhabitat to increase water uptake, or to seek a position for detection of a passing blood-meal source. Spending a long period off the host gives the tick an opportunity to find a suitable species of animal to which to attac.
Ticks as gorging and fasting creatures, are considered to be two exceptionally different animals. A creature that is adapted for existing on a host body as a blood feeder, the other as a conservative one that can survive off the host and has the ability to expand its life strategies to adjust to the availability of water and energy resources to increase its chances of obtaining a blood meal. Diversity in daily and seasonal behaviour influences both physiological ageing and the balance of energy and water resources.
Ticks may have one, two or three-host life cycles, depending on the species:
One-host ticks
Larvae hatch from eggs, climb on to a host, attach, engorge and moult on the host to nymphs. The nymphs re-attach, engorge and moult to males and females on the same host. The adult ticks re-attach to the same host, partially engorge and mate and the females engorge fully. After detaching from the host, the females drop to the ground and deposit eggs and eventually die.
With the elimination of the waiting period for a host and shortening of metamorphosis, the monoxenic cycle on the host is shortened to possibly 3-4 weeks. There are not many one-host species, but some are important from the veterinary point of view. One-host ticks include Rhipicephalus (Boophilus) decoloratus, R. (B.) microplus, and Margaropus species.
Two-host ticks
After the new generation of larvae hatch from eggs laid by females, they climb on to the first host, engorge and moult to nymphs. The nymphs reattach, engorge, detach, drop to the ground and moult to females and males. The adult ticks climb on to the second host, attach, partially engorge and mate. The females engorge fully, detach and drop to the ground and eventually lay eggs that give rise to the next generation. In the dixenic host life cycle, the three stages develop on two different individuals that may or may not belong to the same species. In the first, the engorged larva moults on the host and the nymph reattaches close by. At the end of the blood meal the nymph detaches and metamorphoses on the ground. There are only two searches for a host, which eliminate the risks linked with the need for nymphal host searching and attachment. Hyalomma species and some Rhipicephalus species belong to this group.
Three-host ticks
Briefly, each stage of the parasitic cycle takes place on a different host. The fully engorged females detach from the third host, lay eggs in a sheltered locality and then die. Amblyomma species and the majority of Rhipicephalus species belong to this group. In the life cycle of a three-host tick, which is common to most ticks, host finding occurs three times. The tick requires three hosts (irrespective of the host species) for development and completion of its life cycle. There are three parasitic phases separated by two phases on the ground, when metamorphosis occurs.
Host specificity
Host specificity is defined as an association between tick species and one or a group of vertebrate species for the continuation of ticks` life cycles. Ticks have conventionally been observed as comparatively host-specific and it has generally been believed that their geographic distributions can be determined by that of their host/hosts. The strict or limited degree of host specificity of the majority of tick species (at least 700 out of 800 ixodid species) have been determined.
Host-finding of ambushing tick larvae is achieved by a sequence of behavioural processes. Under natural conditions this behaviour pattern constitutes localization, identification and invasion of the tick’s host.
Hard ticks seek hosts by an interesting behaviour called "questing." Questing ticks crawl up the stems of grass or perch on the edges of leaves on the ground in a typical posture with the front legs extended, especially in response to a host passing by. Subsequently, these ticks climb on to a potential host, which has brushed against their extended front legs. Certain bio-chemicals such as carbon dioxide as well as heat and movement serve as stimuli for host seeking behaviour.
Stage and site specificity
One of the factors limiting the distribution of ticks on the host’s body is the restriction of many tick species to certain parts of the body. This characteristic leads to reduction of the area available for attachment of any particular species.
At the site of attachment, ticks cause skin irritation, which stimulates the animal to groom itself with the tongue. This act successfully limits the number of ticks feeding and engorging on these areas. The common phenomenon of limitation of ticks to certain parts of the host body is thus either due to the host or characteristics of the environment and climate which are considered as evolutionary forces.
Upload your picture of a tick and add a description underneath. Please only do one species per post. All entries will be edited and updated (additional photos and information will be added by moderators). New entries will be posted according to taxonomic order and the post date does not reflect the actual date of new posts.
Ticks are small arachnids in the order Ixodida. Along with mites, they constitute the subclass Acarina. Ticks are ectoparasites (external parasites), living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians.
Morphology of ticks
Ticks are closely related in general body structure to parasitic mites. The separationof ticks from mites is based on two useful morphologic characteristics: firstly the occurrence of a hypostome (ventral mouthpart) that has been modified into a piercing organ (usually with recurved teeth) and secondly the presence of a distinct sensory apparatus (Haller’s organ) on the dorsal aspect of the tarsus of the first leg.
The conscutum covers nearly the entire dorsal surface of male ixodid ticks and so limits the amount of blood that can be ingested. Female ticks and larvae and nymphs also have a scutum, but it covers only the anterior third of the dorsum, thus allowing the tick to expand when engorging.
Life cycle of ticks
There are four stages in the life cycle of an ixodid tick, namely the egg, the larva, the nymph, and the adult. The three instars (larva, nymph and
adult) climb on to the vegetation in order to attach to a passing host or quest for a host from the soil surface. Once on the host, the tick crawls to a predilected feeding site where it cuts the skin with its chelicerae and inserts its hypostome that together with cement secreted by the salivary glands, anchors the tick firmly in place. The tick remains in place for several days (larva, 3–6 days; nymph, 4–7 days; adult female, 7–9 days) during which time active growth of gut and cuticle occurs in order to accommodate the blood meal, most of which will be acquired in the final 24 hours of engorgement. During feeding the blood meal is concentrated by the extraction of water, which is then secreted back into the host by specialised salivary gland cells and is an important means by which tick-borne pathogens invade their hosts. Once fully engorged the tick withdraws its hypostome and falls to the ground where it begins digesting the blood meal and developing to the next instar.
Digestion is slow, and development of the new instars takes several months in temperate regions. The newly moulted (or hatched) unfed tick may remain quiescent for a time, but will eventually ascend the vegetation to quest for a host and a blood meal. After the engorged female detaches from a host digestion of the blood meal and oogenesis take place followed by oviposition. The incubation period of the eggs varies with the species and ambient temperature. Embryogenesis usually lasts 20 – 50 days.
Ixodid ticks have substantial capability to swallow and concentrate a large volume of host blood, their rapid metabolism and body development can explain the on-host intervals. During off-host periods, ticks experience some environmental distress such as climate and temperature. High temperatures and body-water homeostasis are of importance in processes that influence off-host survival. Ticks as a group have this capability to survive without food and/or water longer than most other arthropods. Ixodid species usually spend an annual total of 12-21 days on the host
compared to the off-host period.
Off-host fasting is characterized by slow metabolism with lengthy intervals of immobility, interrupted by movement within the microhabitat to increase water uptake, or to seek a position for detection of a passing blood-meal source. Spending a long period off the host gives the tick an opportunity to find a suitable species of animal to which to attac.
Ticks as gorging and fasting creatures, are considered to be two exceptionally different animals. A creature that is adapted for existing on a host body as a blood feeder, the other as a conservative one that can survive off the host and has the ability to expand its life strategies to adjust to the availability of water and energy resources to increase its chances of obtaining a blood meal. Diversity in daily and seasonal behaviour influences both physiological ageing and the balance of energy and water resources.
Ticks may have one, two or three-host life cycles, depending on the species:
One-host ticks
Larvae hatch from eggs, climb on to a host, attach, engorge and moult on the host to nymphs. The nymphs re-attach, engorge and moult to males and females on the same host. The adult ticks re-attach to the same host, partially engorge and mate and the females engorge fully. After detaching from the host, the females drop to the ground and deposit eggs and eventually die.
With the elimination of the waiting period for a host and shortening of metamorphosis, the monoxenic cycle on the host is shortened to possibly 3-4 weeks. There are not many one-host species, but some are important from the veterinary point of view. One-host ticks include Rhipicephalus (Boophilus) decoloratus, R. (B.) microplus, and Margaropus species.
Two-host ticks
After the new generation of larvae hatch from eggs laid by females, they climb on to the first host, engorge and moult to nymphs. The nymphs reattach, engorge, detach, drop to the ground and moult to females and males. The adult ticks climb on to the second host, attach, partially engorge and mate. The females engorge fully, detach and drop to the ground and eventually lay eggs that give rise to the next generation. In the dixenic host life cycle, the three stages develop on two different individuals that may or may not belong to the same species. In the first, the engorged larva moults on the host and the nymph reattaches close by. At the end of the blood meal the nymph detaches and metamorphoses on the ground. There are only two searches for a host, which eliminate the risks linked with the need for nymphal host searching and attachment. Hyalomma species and some Rhipicephalus species belong to this group.
Three-host ticks
Briefly, each stage of the parasitic cycle takes place on a different host. The fully engorged females detach from the third host, lay eggs in a sheltered locality and then die. Amblyomma species and the majority of Rhipicephalus species belong to this group. In the life cycle of a three-host tick, which is common to most ticks, host finding occurs three times. The tick requires three hosts (irrespective of the host species) for development and completion of its life cycle. There are three parasitic phases separated by two phases on the ground, when metamorphosis occurs.
Host specificity
Host specificity is defined as an association between tick species and one or a group of vertebrate species for the continuation of ticks` life cycles. Ticks have conventionally been observed as comparatively host-specific and it has generally been believed that their geographic distributions can be determined by that of their host/hosts. The strict or limited degree of host specificity of the majority of tick species (at least 700 out of 800 ixodid species) have been determined.
Host-finding of ambushing tick larvae is achieved by a sequence of behavioural processes. Under natural conditions this behaviour pattern constitutes localization, identification and invasion of the tick’s host.
Hard ticks seek hosts by an interesting behaviour called "questing." Questing ticks crawl up the stems of grass or perch on the edges of leaves on the ground in a typical posture with the front legs extended, especially in response to a host passing by. Subsequently, these ticks climb on to a potential host, which has brushed against their extended front legs. Certain bio-chemicals such as carbon dioxide as well as heat and movement serve as stimuli for host seeking behaviour.
Stage and site specificity
One of the factors limiting the distribution of ticks on the host’s body is the restriction of many tick species to certain parts of the body. This characteristic leads to reduction of the area available for attachment of any particular species.
At the site of attachment, ticks cause skin irritation, which stimulates the animal to groom itself with the tongue. This act successfully limits the number of ticks feeding and engorging on these areas. The common phenomenon of limitation of ticks to certain parts of the host body is thus either due to the host or characteristics of the environment and climate which are considered as evolutionary forces.
Male © mposthumus
Male © mposthumus
Female © mposthumus
Female © mposthumus
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