Tarantula & Scorpion WebQuest
Scorpions
Scorpions
are eight-legged
arthropods.
A member of the
Arachnida
class and belonging to the order Scorpiones, there are about 2000 species of
scorpions. They are found widely distributed south of
49°
N, except
New
Zealand and
Antarctica.
The northern-most part of the world where scorpions live in the wild is
Sheerness
on the
Isle
of Sheppey in the
UK,
where a small colony of
Euscorpius
flavicaudis has been resident since the 1860s.
The
cuticle makes a tough armor around the body. In some places it is covered with
hairs that act like balance organs. An outer layer that makes them fluorescent
green under
ultraviolet
light is called the hyaline layer. Newly molted scorpions do not glow until
after their cuticle has hardened. The fluoresent hyaline layer can be intact in
fossil rocks that are hundreds of millions of years old.
The
body of a scorpion is divided into two segments: the
cephalothorax
(also called the prosoma) and the
abdomen/opisthosoma.
The abdomen consists of the
mesosoma
and the metasoma.
The
cephalothorax, also called prosoma, is the scorpion's “head”, comprising the
carapace,
eyes,
chelicerae
(mouth parts),
pedipalps
(claw) and four
pairs of
walking
legs.
The
mesosoma, the abdomen's front half, is made up of six segments. The first
segment contains the
sexual
organs as well as a pair of vestigial and modified appendages forming a
structure called the genital operculum. The second segment bears a pair of
featherlike
sensory
organs known as the pectines; the final four segments each contain a pair of
book
lungs. The mesosoma is
armored
with
chitinous
plates, known as
tergites
on the upper surface and
sternites
on the lower surface.
The
metasoma, the scorpion's
tail,
comprising six segments (the first tail segment looks like a last mesosoman
segment), the last containing the scorpion's
anus
and bearing the
telson
(the
sting).
The telson, in turn, consists of the
vesicle,
which holds a pair of
venom
glands and the hypodermic aculeus, the venom-injecting barb.
On rare occasions, scorpions can be born with two metasomata (tails). Two-tailed scorpions are not a different species, but rather a genetic abnormality.
Most
scorpions reproduce sexually and most species have male and female individuals.
While the majority of scorpion species reproduce sexually, some, such as
Hottentotta
hottentotta,
Liocheles
australasiae,
Tityus
columbianus,
Tityus
metuendus,
Tityus
serrulatus,
Tityus
stigmurus,
Tityus
trivittatus, and
Tityus
urugayensis, all reproduce through
parthenogenesis, a process
in which unfertilized eggs develop into living
embryos.
Parthenogenic reproduction starts following the scorpion's final moult to
maturity and continues thereafter. Sexual reproduction is accomplished by the
transfer of a
spermatophore
from the
male to
the
female;
scorpions possess a complex
courtship
and
mating
ritual to effect this transfer. Mating starts with the
male
and
female
locating and identifying each other using a mixture of
pheromones
and
vibrational
communication; once they have satisfied each other that they are of opposite sex
and of the correct species, mating can commence.
The
courtship starts with the male grasping the female’s pedipalps with his own;
the pair then performs a "dance" called the "promenade à deux".
In reality this is the male leading the female around searching for a suitable
place to deposit his
spermatophore.
The courtship ritual can involve several other behaviours such as
juddering
and a cheliceral kiss, in which the male's chelicerae--clawlike
mouthparts--grasp the female's in a smaller more intimate version of the male's
grasping the female's pedipalps and in some cases injecting a small amount of
his venom into her pedipalp or on the edge of her cephalothorax, probably as a
means of pacifying the female.
When
he has identified a suitable location, he deposits the spermatophore and then
guides the female over it. This allows the spermatophore to enter her
genital
opercula, which triggers release of the sperm, thus fertilizing the female.
The mating process can take from 1 to 25+ hours and depends on the ability of
the male to find a suitable place to deposit his spermatophore. If mating goes
on for too long, the female may eventually break off the process.
Once
the mating is complete, the male and female quickly separate. The male will
generally retreat quickly, most likely to avoid being cannibalized by the
female, although sexual
cannibalism
is infrequent with scorpions.
Compsobuthus
werneri female with young
Unlike the majority of Arachnida species, scorpions are viviparous. The young are born one by one, and the brood is carried about on its mother's back until the young have undergone at least one moult. Before the first moult, scorplings cannot survive naturally without the mother, depending on her for protection and to regulate their moisture levels. Especially in species which display more advanced sociability (e.g Pandinus spp.), the young/mother association can continue for an extended period of time. The size of the litter depends on the species and environmental factors, and can range from two to over a hundred scorplings.
The
young generally resemble their parents. Growth is accomplished by periodic
shedding of the exoskeleton (ecdysis).
A scorpion's developmental progress is measured in
instars
(how many moults it has undergone). Scorpions typically require between five and
seven moults to reach maturity. Moulting is effected by means of a split in the
old
exoskeleton
which takes place just below the edge of the carapace (at the front of the
prosoma). The scorpion then emerges from this split; the pedipalps and legs are
first removed from the old exoskeleton, followed eventually by the
metasoma.
When it emerges, the scorpion’s new
exoskeleton
is soft, making the scorpion highly vulnerable to attack. The scorpion must
constantly stretch while the new exoskeleton hardens to ensure that it can move
when the hardening is complete. The process of hardening is called
sclerotization.
The new exoskeleton does not fluoresce; as
sclerotization
occurs, the fluorescence gradually returns.
Scorpions
have quite variable lifespans and the actual lifespan of most species is not
known. The age range appears to be approximately 4-25 years (25 years being the
maximum reported life span in the species H. arizonensis).Lifespan of Hadogenes
species in wild is estimated to 25-30 years.
Scorpions
prefer to live in areas where the temperatures range from 20°C to 37°C (68°F
to 99°F), but may survive from freezing temperatures to the desert heat.
Scorpions
of genus
Scorpiops
living in hight Asian mounties,Bothriuridae scorpions from Patagonia and smal
Euscorpius
scorpions from middle Europe in Winter survives temperatures about -25°C.
They are nocturnal and fossorial, finding shelter during the day in the relative cool of underground holes or undersides of rocks and coming out at night to hunt and feed. Scorpions exhibit photophobic behavior, primarily to evade destruction by their predators such as birds, centipedes, lizards, mice, possums, and rats.
Scorpions
are opportunistic predators of small arthropods and insects. They use their
chela (pincers) to catch the prey initially. Depending on the toxicity of their
venom and size of their claws, they will then either crush the prey or inject it
with
neurotoxic
venom. This will kill or paralyze the prey so the scorpion can eat it. Scorpions
have a relatively unique style of eating using
chelicerae,
small claw-like structures that protrude from the mouth that are found only in a
handful of invertebrates, including
spiders
and
vinegaroons.
The chelicerae, which are very sharp, are used to pull small amounts of food off
the prey item for digestion. Scorpions can only digest food in a liquid form;
any solid matter (fur,
exoskeleton,
etc) is disposed of by the scorpion.
Venom
All
scorpion species possess
venom.
In general, scorpion venom is described as
neurotoxic
in nature. One exception to this however is
Hemiscorpius
lepturus which possesses
cytotoxic
venom. The neurotoxins consist of a variety of small
proteins
as well as sodium and potassium
cations,
which serve to interfere with neurotransmission in the victim which causes
paralysis without damage to the tissues. Scorpions use
their venom to kill or paralyze their prey so that it can be eaten; in general
it is fast acting, allowing for effective prey capture. The effects of the sting
can be severe.
Scorpion
venoms are optimized for action upon other
arthropods
and therefore most scorpions are relatively harmless to
humans;
stings produce only local effects (such as pain, numbness or swelling). A few
scorpion species, however, mostly in the family
Buthidae,
can be dangerous to humans. Among the most dangerous are
Leiurus
quinquestriatus, otherwise dubiously known as the deathstalker, which has
the most potent venom in the family, and members of the genera
Parabuthus,
Tityus,
Centruroides,
and especially
Androctonus,
which also have powerful venom. The scorpion which is responsible for the most
human deaths is
Androctonus
australis, or the yellow fat-tailed scorpion of
North
Africa. The toxicity of A. australis's venom is roughly half that of L.
quinquestriatus, but despite the common misconception A. australis does not
inject noticeably more venom into its prey. The higher death count is simply due
to its being found more commonly, especially near humans. Human deaths normally
occur in the young, elderly, or infirm; scorpions are generally unable to
deliver enough venom to kill healthy adults. Some people, however, may be
allergic
to the venom of some species. Depending on the severity of the allergy, the
scorpion's sting may cause
anaphylaxis
and death. A primary symptom of a scorpion sting is numbing at the injection
site, sometimes lasting for several days. Scorpions are generally harmless and
timid, and only voluntarily use their sting for killing prey, defending
themselves or in territorial disputes with other scorpions. Generally, they will
run from danger or remain still.
It
should be noted that the family Buthidae, while containing perhaps the highest
number of dangerous species, also contains many species that are not thought to
be medically significant.
Scorpions
are able to regulate how much venom is injected with each sting using striated
muscles in the stinger, the usual amount being between 0.1 and 0.6 mg. There is
also evidence to suggest that scorpions restrict the use of their venom using it
only to subdue large prey, or prey that struggles. It has been found that
scorpions have two types of venom: a translucent, weaker venom designed to stun
only, and an opaque, more potent venom designed to kill heavier threats. This is
likely because it is expensive in terms of energy for a scorpion to produce
venom, and because it may take several days for a scorpion to replenish its
venom supply once it has been exhausted.
There
is currently no equivalent of the
Schmidt
Sting Pain Index because nobody has yet classified the levels of pain
inflicted by different scorpion stings. This is probably because of the risk
involved with some species, such as Androctonus australis or Leiurus
quinquestriatus. However, envenomation by a mildly venomous species like
Pandinus
imperator is similar to a bee sting in terms of the pain and swelling that
results. A sting on the thumb from a relatively non-dangerous scorpion often
feels like the victim has accidentally struck their
thumb
with a hammer whilst driving in a nail. A sting on the thumb from a truly
dangerous scorpion can feel much worse, as though the victim had hammered a nail
right through their thumb. It should be noted that the physical effects of a
sting from a medically significant scorpion are not limited to the pain
inflicted: there can be
bradycardia,
tachycardia
or in severe cases
pulmonary
edema.
The
stings of North American scorpions are rarely serious and usually result in
pain, minimal swelling, tenderness, and warmth at the sting site. However, the
Arizona bark scorpion (Centruroides
exilicauda or sculpturatus), which is found in Arizona and New Mexico and on
the California side of the Colorado River, has a much more toxic sting. The
sting is painful, sometimes causing numbness or tingling in the area around the
sting. Serious symptoms are more common in children and include abnormal head,
eye, and neck movements; increased saliva production; sweating; and
restlessness. Some people develop severe involuntary twitching and jerking of
muscles. Breathing difficulties may occur. The stings of most North American
scorpions require no special treatment. Placing an ice cube on the wound reduces
pain, as does an ointment containing a combination of an antihistamine, an
analgesic, and a corticosteroid. Centruroides stings that result in serious
symptoms may require the use of sedatives, such as midazolam, given
intravenously. Centruroides antivenom rapidly relieves symptoms, but it may
cause a serious allergic reaction or serum sickness. The antivenom is available
only in
Professor
Moshe
Gueron was the first to investigate the Cardiovascular Manifestations Affect
of Severe Scorpion Sting. Thousands
of stung patients were reviewed. Thirty-four patients with severe scorpion sting
were reviewed and pertinent data related to the cardiovascular system such as
hypertension, peripheral vascular collapse, congestive heart failure or
pulmonary edema were analyzed. The electrocardiograms of 28 patients were
reviewed; 14 patients showed "early myocardial infarction-like"
pattern. The urinary catecholamine metabolites were investigated in 12 patients
with scorpion sting. Vanylmandelic acid was elevated in seven patients and the
total free epinephrine and norepinephrine in eight. Six of these 12 patients
displayed the electrocardiographic "myocardial infarction-like"
pattern. Nine patients died and the pathologic lesions of the myocardium were
reviewed in seven. Also, Gueron reported five cases of Severe Myocardial damage
and heart failure in Scorpion sting from
Beer-Sheba,
Israel. He
described hypertension, pulmonary oedema with hypertension, hypotension,
pulmonary oedema with hypotension and rhythm disturbances as five different
syndromes that may dominate the clinical picture in scorpion sting victim. He
suggested that all patients with cardiac symptoms should be admitted to an
intensive cardiac unit. A few years later, at 1990, he was reported poor
contractility with low ejection fraction, decreased systolic left ventricular
performance, lowered fractional percentage shortening observed in
echocardiographic and radionuclide angiographic study. Gueron was questioned
regarding the value of giving antivenom, and he replied that although is freely
available, all cases of scorpion sting are treated without it, and there had not
been a single fatality in 1989.
Scorpions
have been found in many
fossil
records, including coal deposits from the
Carboniferous
Period and in marine
Silurian
deposits. They are thought to have existed in some form since about 425–450
million years ago. They are believed to have an oceanic origin, with gills and a
claw-like appendage that enabled them to hold onto rocky shores or
seaweed.
The
eurypterids,
marine
creatures which lived during the
Paleozoic
era, share several physical traits with scorpions and are closely related to
them. Various species of Eurypterida could grow to be anywhere from 10 cm (4 in)
to 3 m (9.75 ft) in length. However, they exhibit
anatomical
differences marking them off as a group distinct from their Carboniferous and
recent descendants. Despite this, some refer to them as "sea
scorpions." Their legs are thought to have been short, thick, tapering and
to have ended in a single strong claw; it appears that they were well-adapted
for maintaining a secure hold upon rocks or seaweed against the wash of waves,
like the legs of shore-crab.
Hadrurus spadix - Caraboctonidae, Hadrurinae
Scorpions
are almost universally distributed south of 49° N, and their geographical
distribution shows in many particulars a close and interesting correspondence
with that of the
mammals,
including their entire absence from
New
Zealand. The facts of their distribution are in keeping with the hypothesis
that the order originated in the
northern
hemisphere and migrated southwards into the southern continent at various
epochs, their absence from the countries to the north of the above-mentioned
latitudes being due, no doubt, to the comparatively recent
glaciation
of those areas. When they reached
Africa,
Madagascar
was part of that continent; but their arrival in
Australia
was subsequent to the separation of
In the
Five
colonies of scorpions (Euscorpius
flavicaudis) have established themselves in southern
England
having probably arrived with imported fruit from
Africa,
but the number of colonies could be lower now because of the destruction of
their habitats. This scorpion species is small and completely harmless to
humans.
Suicide
misconception
The
belief that scorpions commit suicide by stinging themselves to death when
surrounded by
fire
is of considerable antiquity and is often prevalent where these animals exist.
It is nevertheless untrue since the venom has no effect on the scorpion itself,
nor on any member of the same species (unless the venom is injected directly
into the scorpion's nerve ganglion—quite an unlikely event outside of the
laboratory). The misconception may derive from the fact that scorpions are
poikilotherms (cold-blooded):
when exposed to intense heat their metabolic processes malfunction. This causes
the scorpion to spasm wildly and this spasming may appear as if the scorpion is
stinging itself. It is also untrue that
alcohol
will cause scorpions to sting themselves to death.
A scorpion
under a
blacklight.
In normal lighting this scorpion appears black.
Scorpions
are also known to glow when exposed to certain wavelengths of
ultraviolet
light such as that produced by a
blacklight.
Tarantula
is the common name for a group of "hairy" and often very large
spiders
belonging to the
familyTheraphosidae,
of which approximately 900 species have been identified. Tarantulas hunt prey in
both trees and on the ground. All tarantulas can emit silk, whether they be
arboreal or terrestrial species. Arboreal species will typically reside in a
silken "tube web", and terrestrial species will line their burrows or
lairs with web to catch wandering prey. They mainly eat insects and other
arthropods, using ambush as their primary method. The biggest tarantulas can
kill animals as large as lizards, mice, or birds. Most tarantulas are harmless
to humans, and some species are popular in the exotic pet trade while others are
eaten as food. These spiders are found in tropical and desert regions around the
world.
The
name tarantula comes from the town of
Taranto
in Southern
Italy
and was originally used for an unrelated species of either European
wolf
spider (See
Lycosa
tarantula for more information about this spider the appearance of which
resembles that of that tarantula family) or the
Mediterranean
black widow (the effects of whose bite more closely resemble that described
in Taranto). In
There
are other species also referred to as tarantulas outside this family; the
evolution of the name Tarantula is discussed
below.
This article primarily concerns the Theraphosids.
Like all arthropods, the tarantula is an invertebrate that
relies on an exoskeleton for muscular support. A tarantula’s body consists of
two main parts, the
prosoma or the
cephalothorax (the former is most often used because there is no analogous
"head") and the abdomen or
opisthosoma. The prosoma
and opisthosoma are connected by the
pedicle or what is often
called the pregenital somite. This waist-like connecting piece is actually part
of the prosoma and allows the opisthosoma to move in a wide range of motion
relative to that of the prosom.
Depending
on the species, the body length of tarantulas range from 2.5 - 10 cm (1-4
inches), with 8-30 cm (3 to 12 inch) leg spans (their size when including their
legs). Legspan is determined by measuring from the tip of the back leg to the
tip of the front leg on the same side, although some people measure from the tip
of the first leg to the tip of the fourth leg on the other side. The largest
species of tarantulas can weigh over 9 grams (0.3 ounces). One candidate for the
title of the largest of all species, the
Theraphosa
blondi (goliath birdeater) from
Theraphosa
apophysis (the pinkfoot goliath) was described 187 years after the Goliath
birdeater; therefore its characteristics are not as well attested. However,
legspans of up to 33 cm (13 inches) have been reported for that species. T.
blondi is generally thought to be the heaviest tarantula, and T. apophysis the
largest legspan. Two other species,
Lasiodora
parahybana and
Lasiodora
klugi, (the Brazilian salmon birdeater) gets very large and rivals the size
of both Theraphosa blondi and Theraphosa apophysis, and some have even made
claims to same size and even bigger sizes than the two Theraphosa species.
The
majority of North American tarantulas are brown. Many species have more
extensive coloration patterns, ranging from cobalt blue (Haplopelma
lividum), black with white stripes (Eupalaestrus campestratus or Aphonopelma
seemanni), to metallic blue legs with vibrant orange abdomen (Chromatopelma
cyaneopubescens, green bottle blue). Their natural habitats include
savanna,
grasslands
such as the
pampas,
rainforests,
deserts,
scrubland,
mountains
and
cloud
forests. They are generally divided into terrestrial types that frequently
make burrows and arboreal types that build tented shelters well off the ground.
Sub-adult Female Poecilotheria regalis
The
eight legs, the two
chelicerae
with their fangs, and the
pedipalps
are attached to the prosoma. The chelicerae are two single segment appendages
that are located just below the eyes and directly forward of the mouth. The
chelicerae contain the venom glands that vent through the fangs. The fangs are
hollow extensions of the chelicerae that inject venom into prey or animals that
the tarantula bites in defense, and they are also used to masticate. These fangs
are articulated so that they can extend downward and outward in preparation to
bite or can fold back toward the chelicerae as a butchers knife blade folds back
into its handle. The chelicerae of tarantulas completely contain the venom
glands and the muscles that surround them and can cause the venom to be
forcefully injected into prey.
The
pedipalps are two six–segment appendages connected to the thorax near the
mouth and protruding on either side of both chelicerae. In most species of
tarantula, the pedipalps contain sharp jagged plates used to cut and crush food
often called the
coxae
or
maxillae.
As with other spiders, the terminal portion of the pedipalps of males function
as part of its reproductive system. Male spiders spin a silken platform (sperm
web) on the ground onto which they release semen from glands in their opistoma.
Then they insert their pedipalps into the semen, absorb the semen into the
pedipalps, and later insert the pedipalps (one at a time) into the reproductive
organ of the female, which is located in her abdomen. The terminal segments of
the pedipalps of male tarantulas are larger in circumference than those of a
female tarantula.
A
tarantula has 4 pairs of legs but 8 pairs of total appendages. Each leg has
seven segments which from the prosoma out are: coxa, trochanter, femur, patella,
tibia, tarsus and pretarsus, and claw. Two or three retractable claws are at the
end of each leg. These claws are used to grip surfaces for climbing. Also on the
end of each leg, surrounding the claws, is a group of hairs. These hairs, called
the scopula, help the tarantula to grip better when climbing surfaces like
glass. The fifth pair are the pedipalps which aid in feeling, gripping prey, and
mating for a mature male. The sixth pair of appendages are the fangs.
The
seventh and eighth pairs of appendages are the four spinnerettes, which also are
hypothesized by some to have been leglike appendages. When walking, a
tarantula's first and third leg on one side move at the same time as the second
and fourth legs on the other side of his body. The muscles in a tarantula's legs
cause the legs to bend at the joints, but to extend a leg, the tarantula
increases the pressure of blood entering the leg.
Tarantulas,
like almost all other spiders, have their spinnerets at the end of the
opisthosoma. Unlike spiders that on average have six, tarantulas have two or
four spinnerets. Spinnerets are flexible tubelike structures from which the
spider exudes its silk. The tip of each spinneret is called the spinning field.
Each spinning field is covered by as many as one hundred spinning tubes through
which silk is produced. This silk hardens on contact with the air to become a
thread like substance.
The
tarantula’s mouth is located under its chelicerae on the lower front part of
its prosoma. The mouth is a short straw-shaped opening which can only suck,
meaning that anything taken into it must be in liquid form. Prey with large
amounts of solid parts such as mice must be crushed and ground up or
predigested, which is accomplished by spraying the prey with digestive juices
that are excreted from openings in the chelicerae.
The
tarantula’s digestive organ (stomach) is a tube that runs the length of its
body. In the prosoma, this tube is wider and forms the sucking stomach. When the
sucking stomach's powerful muscles contract, the stomach is increased in
cross-section, creating a strong sucking action that permits the tarantula to
suck its liquified prey up through the mouth and into the intestines. Once the
liquified food enters the intestines, it is broken down into particles small
enough to pass through the intestine walls into the haemolymph (blood stream)
where it is distributed throughout the body.
Nervous system
A
tarantula's central nervous system (brain) is located in the bottom of the inner
prosoma. The central nervous system controls all of the body's activities. A
tarantula maintains awareness of its surroundings by using its sensory organs,
setae. Although it has eyes, a tarantula’s sense of touch is its keenest sense
and it often uses vibrations given off by its prey's movements to hunt. A
tarantula's setae are very sensitive organs and are used to sense chemical
signatures, vibration, wind direction and possibly even sound. Tarantulas are
also very responsive to the presence of certain chemicals such as pheromones.
The
eyes are located above the chelicerae on the forward part of the prosoma. They
are small and usually set in two rows of four. Most tarantulas are not able to
see much more than light, darkness, and motion. Arboreal tarantulas see better
than terrestrial tarantulas.
Respiratory system
In
all types of tarantulas there are two book lungs (breathing organs). The book
lungs are located in a cavity inside the lower front part of the abdomen near
where the abdomen connects to the cephalothorax. Air enters the cavity through a
tiny slit on each side of and near the front of the abdomen. Each lung consists
of 15 or more thin sheets of folded tissue arranged like the pages of a book.
These sheets of tissue are supplied by blood vessels. As air enters each lung,
oxygen is taken into the blood stream through the blood vessels in the lungs.
Needed moisture may also be absorbed from humid air by these organs.
A
tarantula’s blood is unique; an oxygen-transporting protein is present (the
copper-based
hemocyanin)
but not enclosed in blood cells like the erythrocytes of mammals. A
tarantula’s blood is not true blood but rather a liquid called haemolymph, or
hemolymphy. There are at least four types of hemocytes, or hemolymph cells. The
tarantula’s heart is a long slender tube that is located along the top of the
opisthosoma. The heart is neurogenic as opposed to myogenic, so nerve cells
instead of muscle cells initiate and coordinate the heart. The heart pumps
hemolymph to all parts of the body through open passages often referred to as
sinuses, and not through a circular system of blood vessels. If the exoskeleton
were to be breached, loss of hemolymph could kill the tarantula unless the wound
were small enough that the hemolymph could dry and close the wound.
Thermal image of a cold-blooded tarantula on a warm-blooded human
hand
Defense
Besides the normal "hairs" covering the body of tarantulas, some also have a dense covering of irritating hairs called urticating hairs, on the opisthosoma, that they sometimes use as a protection against enemies. These hairs are only present on New World species and are absent on specimens of the Old World.
These
fine hairs are barbed and designed to irritate. They can be lethal to small
animals such as rodents. Some people are extremely sensitive to these hairs, and
develop serious itching and rashes at the site. Exposure to urticating hairs
should be strictly avoided. Species with urticating hairs can kick off these
hairs: they are flicked into the air at a target using their back pairs of legs.
Tarantulas also use these hairs for other means; using them to mark territory or
to line the web or nest (the latter such practice may discourage
flies
from feeding on the spiderlings). Urticating hairs do not grow back, but are
replaced with each molt. The intensity, amount, and flotation of the hairs
depends on the species of Tarantula. Many owners of Goliath Bird Eating Spiders
(Theraphosa Blondi) claim that Theraphosa's have the worst urticating hairs.
To
predators and other kinds of enemies, these hairs can range from being lethal to
simply being a deterrent. With humans, they can cause irritation to eyes, nose,
and skin, and more dangerously, the lungs and airways, if inhaled. The symptoms
range from species to species, from person to person, from a burning itch to a
minor rash. In some cases, tarantula hairs have caused permanent damage to human
eyes.
Tarantula hair has been
used as the main ingredient in the novelty item "itching
powder", Some
tarantula enthusiasts have had to give up their spiders because of allergic
reactions to these hairs (skin rashes, problems with breathing, and swelling of
the affected area).
Some
setae are used to stridulate which makes a hissing sound. These hairs are
usually found on the chelicerae.
Stridulation
seems to be more common in
Despite
their often scary appearance and reputation, none of the true tarantulas are
known to have a
bite
which is deadly to humans. In general the effects of the bites of all kinds of
tarantulas are not well known. While the bites of many species are known to be
no worse than a wasp sting, accounts of bites by some species are reported to be
very painful. Because other proteins are included when a toxin is injected, some
individuals may suffer severe symptoms due to an allergic reaction rather than
to the venom. For both those reasons, and because any deep puncture wound can
become infected, care should be taken not to provoke any tarantula into biting.
Tarantulas are known to have highly individualistic responses. Some members of
species generally regarded as aggressive can be rather easy to get along with,
and sometimes a spider of a species generally regarded as docile can be
provoked. Anecdotal reports indicate that it is especially important not to
surprise a tarantula.
New
World tarantulas (those found in North and
Before
biting, tarantulas may signal their intention to attack by rearing up into a
"threat posture", which may involve raising their prosoma and lifting
their front legs into the air, spreading and extending their fangs, and (in
certain species) making a loud hissing noise called Stridulating. Their next
step, short of biting, may be to slap down on the intruder with their raised
front legs. If that response fails to deter the attacker they may next turn away
and flick urticating hairs toward the pursuing predator. Their next response may
be to leave the scene entirely, but, especially if there is no line of retreat,
their next (or first) response may also be to whirl suddenly and bite.
Tarantulas can be very deceptive in regard to their speed because they
habitually move very slowly, but are able to deliver an alarmingly rapid bite
when sufficiently motivated.
There
are, however, dangerous spiders which are not true tarantulas but which are
frequently confused with them. It is a popular
urban
legend that there exist deadly varieties of tarantulas somewhere in
Encourage
bleeding to wash out the puncture wounds from within, then clean the bite site
with soap and water and protect it against infection. As with other puncture
wounds, antiseptics may be of limited use since they may not penetrate to the
full depth of a septic wound, so wounds should be monitored for heat, redness,
or other signs of infection. Skin exposures to the urticating hairs can be
treated by applying and then pulling off some sticky tape such as duct tape,
which carries the hairs off with it.
If
any breathing difficulty or chest pain occurs, go to a hospital as this may
indicate an
anaphylactic
reaction. As with bee stings, the allergic reaction may be many times more
dangerous than the toxic effects of the venom. If this occurs an
EpiPen
(an autoinjector of epinephrine, also known as adrenaline) should be
administered as soon as possible, as complete airway blockage can occur within
20 minutes of exposure to the allergen.
Sexual dimorphism
Some
tarantula species exhibit pronounced
sexual
dimorphism. Males tend to be smaller (especially the abdomen, which can
appear quite narrow) and may be quite dull when compared to their female counter
parts, as in the species Haplopelma lividum. Mature male tarantulas also have
tibial hooks on their front legs, which are used to restrain the female's fangs
during copulation.
A
juvenile male's sex can be determined by looking at a cast exuvium for
exiandrous fusillae or spermathecae. Ventral sexing is less reliable but if done
correctly, it can be relatively reliable. Males have much shorter lifespans than
females because they die relatively soon after maturing. Few live long enough
for a post-ultimate molt. It is unlikely that it happens much in natural habitat
because they are vulnerable, but it has happened in captivity rarely. Most males
do not live through this molt as they tend to get their emboli, mature male
sexual organs on pedipalps, stuck in the molt. Most tarantulas kept as pets are
desired to be female. Wild caught tarantulas are often mature males because they
wander out in the open and are more likely to be caught while females remain in
burrows. A stressed tarantula huddles up in the corner with its legs tucked
close to it, does not react, or reacts slowly to touch. A dying tarantula will
curl its legs like a clutched hand under it. Its movement is hydraulically
motivated and an extended leg takes more energy than a curled one. Tarantulas do
not die on their backs unless there is trouble molting.
Excessive
dryness can kill tarantulas, especially tropical tarantulas. Although higher
humidity helps with molting, it appears that for many tarantulas, humidity does
not highly affect molting as much as the actual hydration of the tarantula prior
to molting. Most notably though, Theraphosa species must be high in humidity to
molt.
The molting process
Like
other spiders, tarantulas have to shed their
exoskeleton
periodically in order to grow, a process called
molting.
Young tarantulas may do this several times a year as a part of their maturation
process, while full grown specimens will only molt once every year or so, or
sooner in order to replace lost limbs or lost urticating hairs. A tarantula is
obviously going to molt (or "shed, as some call it) when the exoskeleton
takes on a darker shade. If a tarantula previously used its urticating hairs,
the bald patch will turn from a peach color to deep blue.
Tarantulas
may live for years--most species taking 2 to 5 years to reach adulthood, but
some species may take up to 10 years to reach full maturity. Upon reaching
adulthood, males typically have but a 1 to 1.5 year period left to live and will
immediately go in search of a female with which to mate. It is rare that upon
reaching adulthood the male tarantula will molt again. The oldest spider,
according to
Guinness
World Records, lived to be 49 years old
Females
will continue to molt after reaching maturity. Female specimens have been known
to reach 30 to 40 years of age, and have survived on water alone for up to 2.5
years. Grammostola rosea spiders are renowned for going for long periods without
eating.
Reproduction
As
with other spiders, the mechanics of intercourse are quite different from those
of mammals. Once a male spider reaches maturity and becomes motivated to mate,
it will weave a web mat on a flat surface. The spider will then rub its abdomen
on the surface of this mat and in so doing release a quantity of semen. It may
then insert its pedipalps (short leg-like appendages between the chelicerae and
front legs) into the pool of semen. The pedipalps absorb the semen and keep it
viable until a mate can be found. When a male spider detects the presence of a
female, the two exchange signals to establish that they are of the same species.
These signals may also lull the female into a receptive state. If the female is
receptive then the male approaches her and inserts his pedipalps into an opening
in the lower surface of her abdomen, called the Opithosoma. After the semen has
been transferred to the receptive female's body, the male will swiftly leave the
scene before the female recovers her appetite. Although females may show some
aggression after mating, the male rarely becomes a meal.
Females
deposit 50 to 2000 eggs, depending on the species, in a silken egg sac and guard
it for 6 to 7 weeks. During this time, the female will stay very close to the
eggsac and become more aggressive. The female turns the eggsac often, which is
called brooding. This keeps the eggs from deforming due to sitting too long. The
young spiderlings remain in the nest for some time after hatching where they
live off the remains of their yolk sac before dispersing.
Tarantulas
as Pets
|
adult
Mexican Redknee |
Chilean
Rosehair |
Tarantulas
can be kept as
pets
and are considered good "apartment pets" by many, being quiet animals,
requiring surprisingly little maintenance or cleaning, since unlike
snakes
and
lizards
they have no detectable odor. Because of their docile behavior, the species most
commonly kept as pets are the
Chilean
rosehair tarantula (Grammostola rosea), for their price and the
Mexican
redknee tarantula (Brachypelma smithi), for their beauty. These two species
are also some of the easier to care for and are usually easy to handle, while
other species (Including most Asian species, such as the
cobalt
blue tarantula) are more aggressive and shouldn't be handled. Some of the
more docile types seem to have a habit of relaxing in people's hands, perhaps
attracted by the warmth.
Tarantulas
make quite inexpensive pets. Most species can be purchased as juveniles for
$20-$50 USD. Adults can be quite expensive as they approach breeding age, and
adults of many species can easily reach the several hundred US dollar range.
Housing for most species can cost another 40 USD.
A
terrarium
with an inch or two of damp ground coconut fiber, or a mixture of soil and
sphagnum
moss (but not with cedar shavings as they are toxic to many spiders) on
bottom provides an ideal habitat. (Burrowing tarantulas will require a much
deeper layer.) Harder substances such as gravel and sand are not suitable for a
thriving tarantula; If a tarantula falls too far into a hard surface it can
easily injure itself. Sand doesn't hold moisture well and tarantulas are
generally prone to dehydration. Ambient temperature and humidity vary by
species, with most thriving between 75 degrees and 80°F
(24 to 27°C)
and between 40% and 80% humidity.
Tarantulas can be fed living animals such as insects, small mice or Pinky Mice, and small fish in the water bowl. A tropical roach colony is a good way to maintain a food supply for a number of tarantulas. The discoid cockroach and death's head cockroach in particular are very easy to care for and will not infest the home if they escape. The death's head cockroaches can be kept in an aquarium with no lid since they cannot climb glass and don't fly. Maintaining a colony of death's head cockroaches only requires keeping them in the dark, feeding them a handful of dog food every couple of weeks and misting them with water every day or two.
Other
tarantulas that may make interesting pets are the
Brazilian
whiteknee tarantula,
Chaco
golden knee, and
Brazilian
salmon pink birdeater. These are three of the larger species, each growing
over 8 inches with the Brazilian birdeater sometimes reaching 10 inches and
considered by many to be the largest species that is docile enough to handle.
The foregoing are terrestrial tarantulas, i.e., they generally live in burrows
or natural shelters near the ground. Arboreal tarantulas require different
housing since, when adult, they make webbed shelters well above ground. Those
include Avicularia avicularia and Avicularia metallica, which are generally
quite calm and rarely bite. (Any spider will bite if it is being hurt or put in
fear for its life.) The arboreal spiders can have large legspans, but their
bodies are much less massive than the typical terrestrial tarantulas.
Avicularia
metallica, immature female
The
Goliath
birdeater tarantula (Theraphosa Blondi) is considered a delicacy by the
indigenous
Piaroa
of
Venezuela.
Another appearance of the tarantula as food was made on
Anthony
Bourdain's
A
Cook's Tour.
Fried
tarantulas are also considered a delicacy in
Cambodia.
Etymology
The
word tarantula applies to several very different kinds of
spider.
The spider originally bearing that name is one of the
wolf
spiders,
Lycosa
tarantula, found in the region surrounding the city of
Taranto
(or Tarentum in Latin), a town in Southern
Italy.
Compared to true tarantulas, wolf spiders are not particularly large or hairy.
The
bite of L. tarantula was once believed to cause a fatal condition called
tarantism,
whose cure was believed to involve wild dancing of a kind that has come to be
identified with the
tarantella.
However, modern research has shown that the bite of L. tarantula is not
dangerous to human beings. There appears to have existed a different species of
spider in the fields around
When
theraphosidae were encountered by European explorers in
the
Americas, they were named "tarantulas". Nevertheless, these
spiders belong to the suborder
Mygalomorphae,
and are not at all closely related to wolf spiders.
The
name "tarantula" is also applied to other large-bodied spiders,
including the purseweb spiders or
atypical
tarantulas, the funnel-web tarantulas (Dipluridae
and
Hexathelidae),
and the
dwarf
tarantulas. These spiders are related to true tarantulas (all being
mygalomorphs), but are classified in different
families.
Huntsman
spiders of the family
Sparassidae
are also informally referred to as "tarantulas" because of their large
size. They are not related, belonging to the suborder
Araneomorphae.
