Tarantula: Characteristics, Habitat, Species, Behavior

The tarantula is an arachnid that belongs to the Theraphosidae family. It is the largest animal in its group, highlighting its legs, which can reach 30 centimeters in the case of the Goliath tarantula. Its body consists of two parts, the cephalothorax and the abdomen, in which there are numerous urticarial hairs.

It lives in subtropical, tropical and desert areas of almost every continent, except Antarctica . In these regions, it is found in savannas, grasslands, and in mountainous areas. It usually lives on the ground, specifically in burrows lined with silk threads.

The tarantula can often go out at night to hunt its prey. At that time, she could enter the city and come into contact with people. In relation to its diet, it is based on insects and other arthropods, such as millipedes. Those larger tarantulas hunt lizards, snakes, and mice, among others.

characteristics

– Body

Like all arthropods, the tarantula has an exoskeleton that supports its muscular system. The body consists of two sections, the cephalothorax or prosoma and the abdomen or opisthosoma.

Both parts of the body are connected by a pregenital somite or pedicel. This gives the abdomen a wide range of motion compared to a cephalothorax.

– Size

The size can vary considerably depending on the species, however, the length of the body can be between 2.5 to 10 centimeters. In relation to their legs, they measure from 8 to 30 centimeters.

Larger tarantulas could weigh more than 85 grams. However, the Goliath tarantula ( Theraphosa blondi ), which lives in Brazil and Venezuela, weighs approximately 170 grams and its limbs can measure up to 30 centimeters.

– Coloring

Most North American tarantulas are brown in color, however, in other regions they present different shades. For example, Cyriopagopus lividus is cobalt blue, Aphonopelma seemanni is black with white bands, and Eupalaestrus campestratus has yellow markings on its legs.

Other species are characterized by their vibrant and contrasting colors, such as Chromatopelma cyaneopubescens , whose legs are metallic blue, the abdomen is orange, and the prosoma is green.

– Sexual dimorphism

Some tarantulas exhibit marked sexual dimorphism. Males are usually smaller than females, especially in the abdomen area. In addition, these can have a more opaque color, as occurs in Haplopelma lividum .

On the other hand, some males have tibial hooks on the front legs, which they use to support the female’s fangs while they copulate. Another difference is in the legs, the females have them shorter than the males.

– Appendices

The tarantula has several appendages, such as legs, two pedipalps, and two chelicerae with their fangs. All of these are attached to the prosoma.

Cheliceros

The chelicerae are located under the eyes, in front of the mouth. Inside, they contain poisonous glands, which release the poison through the fangs.

These teeth, which are a hollow extension of the chelicerae, are articulated in such a way that they can extend outwards and downwards, to be used in the event of needing to bite another animal.

Pedipalps

In relation to pedipalps, they are formed by 6 segments attached to the thorax, in the area near the mouth. In the vast majority of species, pedipalps contain sharp, jagged plates that are used to grind and cut food.

In the same way as other male spiders, the terminal ends of the pedipalp function as part of the reproductive system.

Legs

The tarantula has 4 pairs of legs. Each limb has 7 segments, which, from the cephalothorax outwards, are: coxa, trochanter, femur, patella, tibia, tarsus – pretarsus and claw. Around it, it has a group of hairs, called the scapula. These help the arachnid to climb on smooth surfaces, such as glass.

To walk, the first and third legs on one side move in unison with the second and fourth legs on the other side of the body.

– Rows

The rows are flexible structures that are tube-shaped, where the silk is exuded. The tarantula has two to four rows, located at the end of the opistosome.

The end is covered by up to 100 tubes, through which it secretes the silk. While this is extracted, the cutting forces cause the crystallization of the proteins that form it, transforming it from a fine thread to a solid one.

– Internal anatomy

Circulatory system

The fluid that flows in the tarantula’s circulatory system is hemolymph. In this, hemocyanin, which carries carbon dioxide and oxygen, contains copper. This element makes the circulatory fluid have a bluish color.

As for the heart, it is a long, thin tube, located throughout the upper abdomen. It is a neurogenic organ, so its movements are governed by nerve cells. 

The circulatory system lacks blood vessels. In place of these, the heart pumps the hemolymph throughout the body through open tubes.

Nervous system

In the tarantula, the main organ of the nervous system , the brain, is located in the lower part of the cephalothorax. To perceive the environment, it does so through the sensory organs, known as mushrooms.

These structures are highly sensitive and pick up vibrations, chemicals such as pheromones, wind direction, and vibrations.

The eyes are located in the upper part of the chelicerae, towards the front area of ​​the cephalothorax. They are small in size and are usually arranged in two rows of four. The vast majority of tarantulas can only distinguish light, movement, and dark.

Despite the fact that this arachnid has eight eyes, the sense of touch is the most developed. To locate its prey, it uses the vibrations that they make while they move.

Respiratory system

Tarantulas have two sets of lungs. The first pair is located within a cavity located in the lower frontal area of ​​the opisthosoma. As for the second pair of lungs, it is located further behind the abdomen.

Each lung is made up of a tissue folded into 5 or more thin sheets, which are arranged like the pages of a book. Air enters the body through a slot located in the abdomen, known as the pulmonary opening, which expands or contracts as required.

Oxygen is incorporated into the hemolymph, where it is bound by a protein called hemocyanin. Gaseous exchange occurs during the haemolymph travel throughout the body.

– The mute

Like other spiders, tarantulas shed their exoskeleton periodically to grow, a process known as molting. This begins when the exoskeleton takes a darker color. Also, the animal stops feeding and becomes lethargic.

Young people can go through this process several times, while in adulthood it occurs annually. The male seldom molts once he is sexually mature, while the female continues to molt once adult.

– Urticarial hairs

In addition to the fur that covers its body, the tarantula has developed specialized urticarial hairs, which it uses to defend itself from predators. These are located in the opistosome, from where the arachnid takes them to launch them on its attacker.

Also, he could simply rub his body against that of the enemy and thus drive him away, due to the reactions that these irritating hairs provoke in his body. In some species it can cause fatal injuries, especially in small ones, such as rodents.

When urticarial hair comes into contact with the human body, it could cause irritation of the nose, eyes and skin. If they are inhaled, they dangerously affect the respiratory tract, mainly the lungs.

This fur, once the tarantula removes it from its body, is not reborn. They are replaced again at the time of the move.

These hairs are typical of the New World tarantulas, which inhabit North, Central and South America. While those of the Old World, which lack this type of bristle, they generally attack by biting with their fangs when they feel threatened.

Types

The researchers propose the existence of four types of urticarial hairs, indicating that a tarantula could have several classes of these specialized bristles.

– Type I hairs. These penetrate the skin with little depth, thus causing mild reactions. They are generally found in species that inhabit the United States.

– Type II hairs. The main characteristic of this type of sow is that it forms part of the silk lining that covers the refuge, the silk mat used by the male in reproduction and the egg sacs.

– Type III hairs. These can enter the skin to a depth of 2 millimeters, causing incessant hives and inflammation in the area, which could last two to three weeks. They are usually present in the Caribbean, Mexican, South American and Central American species.

– Type IV hairs. When these are inhaled, they cause inflammation in the respiratory tract of small mammals, although specialists do not know if they have the same effect in humans.

– Bites

The effects of tarantula bites can vary, depending on the species. Some of these may only cause mild discomfort, while others may cause severe pain and severe spasms, which persist for days.

Also, they could produce hallucinations, as occurs with the venom of the African tarantula Pelinobius muticus . In addition, the fangs of this arachnid usually cause very painful puncture wounds, prone to bacterial infections.

Before biting, the tarantula assumes a threatening posture, raising its cephalothorax and front legs, at the same time spreading its fangs and hissing stridulatingly.

Also, it could hit the attacker with the forelimbs. If this fails to deter the intruder, it may suddenly turn the prosome and bite the animal.

Habitat and distribution

Distribution

Worldwide there are about 1000 species of tarantulas. These are distributed in the great majority of the continents, with the exception of Antarctica.

Other species can be found in Africa, Australia, and much of the Asian continent, including the Ryukyu Islands, south of Japan. In Europe, they are found in Cyprus, Spain, Turkey, and southern Italy.

In relation to the United States, they live in Utah, California, Arizona, Texas, New Mexico and Oklahoma. The eastern boundary is in Louisiana, Arkansas, and Missouri. Also, some tarantulas have been accidentally introduced to Florida.

Habitat

The habitat is very diverse, consisting of savannas, deserts, rainforests, grasslands, scrublands, mountainous regions, and forests. Sometimes it could be found in buildings and settlements, motivated by the invasion of its natural space and the lack of food.

It lives in shady wooded areas and dry deciduous forests, where there may be thorny scrub-type vegetation, with a canopy of deciduous and palm trees.

As for the burrow, generally this arachnid usually modifies the one that it finds empty on the slopes of the pastures, although it could also dig it. Also, it usually takes advantage of small natural cavities, such as those that exist in the roots of trees and in large rocks.

Representative species

Chilean rose tarantula ( Grammostola rosea )

It is a tarantula that measures approximately 8 centimeters. The opisthosoma and the legs are dark brown, with some hairs tinged with pink. However, they could also be reddish, gray, or coppery. In the upper part of the abdomen it has a silver colored region, with stinging bristles.

It lives in Chile, Paraguay, Brazil, Uruguay, Argentina and Mexico. In these regions it lives in deciduous forests and on grasslands, where it usually makes its burrow. To defend itself from its attacker, it projects its stinging bristles against it.

Cobalt blue tarantula ( Haplopelma lividum )

This species inhabits Vietnam, Cambodia, and Asia. Regarding its size, in the adult stage, the female can measure 14 centimeters and the male has an approximate length of 12 centimeters. In relation to food, it eats tenebrios, cockroaches, crickets and small reptiles.

Its coloration varies with the incidence of light, which makes the black color of its body appear bright blue under these conditions. It is an arachnid with an aggressive behavior, with very fast movements that it uses to attack its prey and inoculate it with its powerful venom.

Pink-legged tarantula ( Avicularia avicularia )

This little tarantula lives in South America and the southern Caribbean. At birth they have a pink body and dark legs, but as they age, their coloration changes. Once adult, the body turns dark and the extremities pink.

Goliath tarantula ( Theraphosa blondi )

The giant tarantula, as this species is also known, lives in the South American jungles, specifically in Venezuela, Brazil, Guyana, Colombia and Argentina. Its diet is based on invertebrate animals such as earthworms, although it also eats small rodents, snakes, or lizards.

Its legs measure approximately 30 centimeters and it can weigh 170 grams. It has a brown body and is covered with urticarial hairs, which are used to defend itself from aggressors.

State of conservation

A large number of species in the Theraphosidae family are threatened with extinction. This is why the IUCN, taking into consideration the studies on the population decline of each species, has included several tarantulas in its list of animals at risk of extinction.

Within the group of species of least concern are Brachypelma fossorium lset and Brachypelma epicureanum lset. Other tarantulas, such as Poecilotheria striata and Grammostola vachoni , are vulnerable to extinction.

On the other hand, the populations of Poecilotheria metallica and Poecilotheria hanumavilasumica have decreased dramatically, so they are critically threatened with extinction as a species.

Threats

Degradation and loss of habitat are the main factors affecting this arachnid. Thus, its development is influenced by grazing, agricultural and mining activities.

The use of the environment for human settlements results in the tarantula living or moving in buildings and farms, being able to use some dark and secluded spaces as burrows. Due to this raid, the locals capture and kill her to avoid being bitten.

Among the alterations that man makes in the environment is the construction of roads. In this sense, the male wanders through the area in search of a mate. During attempts to move through the region, he could cross the tracks and be run over, causing his death.

In those tourist regions, such as those in Yucatan, Mexico, deforestation of the coastal area and recreational activities have had a negative impact on numerous subpopulations of B. epicureanum .

Other factors

An additional threat to the tarantula is its capture to be marketed as a pet, both nationally and internationally.

In addition, recently some subpopulations have been affected by natural phenomena that occur in the area, such as floods and man-made fires, as part of their treatment of farmland.

Reproduction

The mating ritual is very different from the rest of the arachnids. Before reproducing, the male spins a special web and releases it on the ground, to then spray it with his sperm. Afterwards, she rubs her pedipalps on the silk fabric, loading them with seminal fluid.

Next, he begins to search for a female, using the pheromones emitted by her as a guide. The female, if she is receptive, comes out of the burrow and at that moment the male will begin to make several exhibitions, to woo her.

These behaviors include lifting the abdomen, lowering the cephalothorax, moving from side to side, and shaking the pedipalps.

It then copulates with the female, holding its fangs with its legs. The male inserts his semen-filled pedipalps into the opening located in the lower abdomen of the female, called the opistosome.

Eggs and hatchlings

The females deposit between 50 and 2,000 eggs, depending on the characteristics of each species. They do this in a silk sack, which they protect for six to eight weeks. In that time, the mothers stay very close to the eggs, becoming somewhat aggressive towards anyone who tries to get close.

A behavior carried out by the female in this stage is to regularly rotate the sac with the eggs, thus preventing them from deforming by maintaining the same position for a long time. After birth, the young remain in the nest for a time, where they feed on the remains of the yolk sacks.

Feeding

Digestive system

The tarantula’s mouth is located below the chelicerae, at the front and bottom of the prosoma. This organ is a short opening, which only has the ability to suck, so its food must be in liquid form.

In the case that the prey has large amounts of solid parts, as in rodents, the tarantula crushes them.

As for the stomach, it is a tube that runs through the entire body. In the abdominal region, it widens and forms the suction stomach. When the muscles of this organ contract, an increase in cross section occurs, creating a strong suction action.

Thanks to this force, the tarantula can suck the prey that has been previously liquefied through its mouth and direct the food towards the intestines. In this, large nutritional particles are broken down into smaller ones, so that they can pass through the walls of this organ and become part of the hemolymph.

Habits

Tarantulas feed primarily on insects and other arthropods, such as spiders, millipedes, and centipedes. Larger ones can hunt and consume small vertebrates , including mice, birds, lizards, bats, and small snakes.

Unlike other species of spiders, tarantulas do not use webs to capture their prey. To hunt her down, they wait for her to approach her to surprise her ambush. Then they grab her with their paws, inoculate her with the poison, and when she is paralyzed, they kill her with their fangs.

Once the animal dies, they inject various digestive enzymes that help to liquefy the body, to be able to suck it with their mouth, which is shaped like a tube. Some genera hunt in trees, while others hunt on the ground or in an area close to it.

Behavior

In general, the tarantula is a not very aggressive animal. However, when threatened, it uses its hind legs to rub them on the stinging hairs on its abdomen and then flings them into the air towards its attacker. In this way, this behavior works as a very effective deterrent against predators.

During the warmer months, sexually mature males begin their quest to find a reproductive partner. Thus, they leave the security they have in the burrow to roam around the area where they live all day.

If on the way they come across a female bulldozer, they hit the ground with their feet, announcing their presence on the site. Once the couple has copulated, the male quickly escapes from the female, since he could be aggressive and attack him, even eating him.

For the female, the male could represent a good source of nutrients, which she will need for the successful completion of the reproductive process.

References 

  1. Wikipedia (2019). Tarantula. Recovered from en.wikipedia.org.
  2. Jessie Szalay (2019). Tarantula Facts. Recovered from livescience.com.
  3. Gary R. Mullen (2002). Spiders (Araneae). Science direct. Recovered from sciencedirect.com.
  4. Ariane Dor, Yann Hénaut (2012). Silk use and spiderling behavior in the tarantula Brachypelma vagans (Araneae: Theraphosidae). Recovered from scielo.org.mx.
  5. Ferretti, NE, Pompozzi, G. (2012). Grammostola vachoni. The IUCN Red List of Threatened Species 2012. Recovered from iucnredlist.org.
  6. Gary R. Mullen, Richard S. Vetter (2019). Spiders (Araneae). Science direct. Recovered from sciencedirect.com.
  7. Molur, S., Daniel, BA, Siliwal, M. (2008). Poecilotheria metallica. The IUCN Red List of Threatened Species 2008. Recovered from iucnredlist.org.
  8. Debbie Hadley (2019). Tarantulas Rarely Bite (And Other Facts About the Friendly Spiders). Recovered from thoughtco.com.

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