Scorpion

Scorpions belong to a group referred to as the Arachnids. Scorpion has eight legs, no wings, and the cephalothorax and the abdomen as the two body parts. The head is fused together with the thorax.

Is Scorpion Insect or Not?

The basic morphology of insects is - six legs, one or two pairs of wings and three body regions namely the head, thorax and abdomen. 

So, from this definition of insect, we can conclude that Scorpion is not an insect. It belongs to a class called Arachnids which are joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata.

Scorpion Classification

With many additions and much reorganization of taxa in the 21st century, about 22 families comprising over 2,500 species of scorpions have been described so far. There are more than 100 described fossil scorpion taxa.

• The Phylum of Scorpion is Arthropoda.

• The Subphylum is Chelicerata.

• The Class of Scorpion is Arachnida.

• The scorpion scientific name is Scorpiones. 

Morphology of Scorpion

The detailed scorpion information can be studied under morphology. Scorpions vary in size from 8.5 mm (0.33 in) to 23 cm (9.1 in). A scorpion's body is divided into two sections or tagmata: the cephalothorax or prosoma and the opisthosoma or abdomen.

The opisthosoma is subdivided into a large anterior section, the mesosoma or pre-abdomen, and the metasoma or post-abdomen, a small tail-like posterior portion. In most species, external variations between the sexes are not evident. For others, the metasoma in males is more elongated than in females.

[Image will be uploaded soon]

Let us Study in Detail the Two Main Sections of a Scorpion.

Cephalothorax or Prosoma

• The mouth sections (carapace, eyes, chelicerae), pedipalps and four pairs of walking legs form the cephalothorax.

• On the top of the cephalothorax, the scorpions have two eyes, and normally two to five pairs of eyes in the front corners of the cephalothorax.

• There are chelicerae on the front and under the carapace. They are pincer-like and have sharp teeth and three segments.

• At the back of the cephalothorax, just behind the oesophagus, is the brain of a scorpion.

• For prey immobilization, protection, and sensory purposes, the pedipalp is segmented and used as a clawed appendage.

• Coxa, trochanter, femur, patella, tibia, and tarsus are the segments of the pedipalp.

• On the pedipalp segments and other parts of the body, a scorpion has darkened or granular raised linear ridges called keels or carinae. These are useful as taxonomic characters.

• The legs are coated in proprioceptors, sensory setae, and bristles. The legs can have spines and spurs, depending on the species.

Mesosoma or Pre-abdomen

• A large portion of the opisthosoma is mesosoma or pre-abdomen.

• It consists of the opisthosoma's anterior seven somites (segments), each of which is covered dorsally by its tergite, a sclerotised plate.

• Somites 3 to 7 are armoured with corresponding plates called sternites at the ventral level. Somite 1's ventral side has a pair of gonopore-covering genital opercula.

• The basal plate with the pectins, which act as sensory organs, is created by Sternite 2.

• Four subsequent somites, 3 to 6, all bear pairs of spiracles. They act as openings for the respiratory organs of the scorpion, known as the lungs of the novel.

• According to the species, the spiracle openings can be slits, circular, elliptic or oval.

• The 7th and final somite does not bear appendages or any other essential external structures.

• The mesosoma includes the heart or dorsal vessel that is the centre of the open circulatory system of the scorpion. The heart, with a deep arterial system that extends across the body, is continuous. Sinuses carry deoxygenated blood or hemolymph back to the heart cardiac pores re-oxygenate the hemolymph.

• The mesosoma comprises the reproductive system as well.

• The female gonads are made of three or four tubes that are connected by two to four transverse anastomoses, running parallel to each other. The sites for both oocyte formation and embryonic growth are these tubes. Two oviducts that attach to a single atrium leading to the genital orifice are linked to them.

• Males have two gonads consisting of two ladder-like cylindrical tubes; they contain spermatozoa-producing cysts. Both tubes, one on either side of the mesosoma, end in a sperm duct. They attach to the paraxial organs called glandular symmetrical structures, which end at the genital orifice. These secrete structures based on chitin that come together to form the spermatophore.

Metasoma or Post-abdomen

• The metasoma or tail is made up of five segments and the telson.

• The five segments are essentially rings of the body; they lack obvious sterna or terga and become distally larger. For taxonomic classification, these segments have keels, setae and bristles that can be used.

• The anus is at the last segment's distal and ventral end, and four anal papillae and the anal arch are encircled. 

• Some species' tails contain light receptors.

• The vesicle, comprising a symmetrical pair of venom glands, forms the telson. The curved stinger, the hypodermic aculeus, equipped with sensory fur, holds it externally.

• Each of the venom glands has its own conduit from the bulb of the gland to the immediate subterminal point of the aculeus, where each of the paired ducts has its own venom pore, to transmit its secretion along the aculeus.

• In the tail, an extrinsic muscle system pushes it forward, propels and penetrates the aculeus, while an intrinsic muscle system attached to the glands pumps venom through the intended victim through the stinger.

• The stinger contains zinc-containing metalloproteins, hardening the blade.

• Relative to the tip, the optimum stinging angle is about 30 degrees.

Types of Scorpions

There are around 2500 varieties of scorpions found till now. The list gives the few major scorpion species. The name inside the parentheses is the scientific name of the scorpion. The types of scorpions are as follows:

1. Emperor scorpion (Pandinus imperator)

It is one of the world's largest scorpions and has a lifespan of 6-8 years. Its body is black, but under ultraviolet light, it glows pastel green or blue, like other scorpions. In the pet trade, it is a common species.

2. Tanzanian red clawed scorpion (Pandinus cavimanus)

Their sting is stated to be the same severity as a bee sting and is not recommended for people who are inexperienced scorpion owners. Red claw scorpions are easily rendered aggressive.

3. Blue scorpion (Rhopalurus junceus)

It is an endangered species, one of the 36 scorpion species found in Cuba, the Dominican Republic and parts of Central America. 

4. Arizona bark scorpion (Centruroides sculpturatus)

It is a small light brown scorpion, widespread in the southwestern United States and northwestern Mexico to the Sonoran Desert. The length of an adult male can exceed 8 cm, whereas that of a female may be slightly smaller, with a maximum length of 7 cm.

5. Pseudoscorpion (Pseudoscorpionida)

It is sometimes referred to as a false scorpion or book scorpion. They are small arachnids that resemble those of scorpions with a flat, pear-shaped body, and pincer-like pedipalps. They typically vary in length from 2 to 8 millimetres (0.08 to 0.31 in).

6. Giant forest scorpion (Heterometrus swammerdami)

At 23 cm in length, this species of scorpion holds the record for being the largest scorpion species in the world, and it can weigh as much as 56 g.

7. Tailless whip scorpions (Amblypygi)

The word "amblypygid" means "blunt tail" a reference to a lack of whip scorpions that is otherwise seen in the flagellum. To humans, these scorpions are harmless.

8. Fattail scorpion (Androctonus)

This is one of the world's most dangerous classes of scorpion species. They are present in the Middle East and Africa's semi-arid and arid areas.

9. Deathstalker (Leiurus quinquestriatus)

It is also known as the yellow scorpion of Palestine, the scorpion of Omdurman, the desert scorpion of Naqab, and several other colloquial names, usually derived from the animal's commercial captive trade.

10. Striped bark scorpion (Centruroides vittatus)

The striped bark scorpion is an extremely common scorpion found in the mid-section of northern Mexico and the United States. It is also the scorpion most commonly found in the United States.

11. Giant hairy scorpion (Hadrurus arizonensis)

This is North America's largest scorpion, and one of the 8-9 Hadrurus species in the United States, reaching 14 cm in length.

Scorpion Facts About Mating and Reproduction

• Males employ chemical attractants called pheromones to express their interest in a female scorpion. They also send off concentrated sensations in the body.

• The male uses his pedipalps to hold onto the pedipalps of the female when a female is found. They perform a dance while holding on to each other. The male then leads them to a place where he deposits his sperm.

• Inside a system called a spermatophore, the sperm is contained. The female draws sperm into her genital pores while in contact with it, fertilizing the eggs. The mating phase may last over 24 hours for some species.

• Within the body of the female, the fertilized eggs develop. The gestation can take a few months to as long as one year, depending on the species.

• When young scorpions are born, they look like a tiny version of their parents. The nymphal-stage scorpions climb up onto their mother's back shortly after birth. They stay there until they moult for the first time.

• The nymphs climb down after the first moult, which happens about two weeks after birth, and scatter. Scorpions usually moult five or six times during their life cycle before they reach maturity.

• Although scorpions grow slowly, in contrast to spiders and insects, they have long lives. 

What is the Scorpion Lifespan? 

Scorpions, relative to other invertebrates, are unusually long-lived. Within 1-3 years, most scorpions reach maturity and live as adults for 1-3 years. This means that scorpions can live for 2-6 years, but there is less research on the life spans of scorpions. Some organisms like the slow-growing Hadogenes will certainly get older. It is important to remember that the growth of scorpions depends on many variables, such as temperature, access to food, reproduction, stress, etc. In captivity, scorpions get older than in nature. Female scorpions live longer than male scorpions. There are few species that have a lifespan of 20-25 years.

Fun Scorpio Facts

• When exposed to certain wavelength ranges of ultraviolet light such as the one produced by a black light, Scorpions glow a bright blue-green due to the presence of fluorescent chemicals in the cuticle.

• Scorpions don’t have any bones but they have an exoskeleton made of chitin, which is similar to the shell of a shrimp.

• Scorpions have two venom glands that are used in hunting and self-defence to produce venom.

• Scorpions are a very old group of animals, appearing in the Siluary period (more than 400 million years ago). Long before the Dinosaurs, they were alive.

• There is venom in all scorpions, but only a small number will cause extreme morbidity in humans. The majority of scorpions are dangerous only to their victims.

• While scorpions develop slowly, they have long lives, in comparison to spiders and insects. Usually, Scorpions live for 3 to 5 years, but some can live for as long as 20-25 years.