Camel spider characteristics, habitat, reproduction, behavior

2008
Sherman Hoover

The camel spiders they are arachnids that make up the order Solifugae (solifugal). This order represents a cursorial group of arachnids with a singular primitive appearance. Around 12 families have been described, with between 900 and 1100 species distributed in America, Europe, Asia and Africa..

As in the rest of the arachnids, camel spiders have a different body in two regions or tagmas with different structural and functional units that are the prosoma or cephalothorax and the opistosoma or abdomen. Additionally, the surface of the body is covered by a series of spines and mushrooms..

South African camel spider By Bernard DUPONT from FRANCE [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)]

In general, these animals have nocturnal habits, although many described species are diurnal. The latter have been observed with peaks of activity during the hottest hours of the day, and are also known as sun spiders..

Except for one species (Rhagodima nigrocincta), solifuges do not have venom glands. However, this species has been little studied in these aspects.

Solifuges have several common names awarded in different parts of the world that refer to some of their outstanding characteristics. The common name "camel spider" refers to a highly arched structure or plate found on the prosoma of many species. They are also known as wind spiders due to their speed when moving.

Solifuges build shelters among the rocks using their chelicerae to dig or even to move small stones or debris. These animals can build up to 40 shelters in their lifetime. In some cases, they can remain in these burrows for up to nine months, although in general they spend little time in them..

Article index

  • 1 General characteristics
    • 1.1 Prosoma
    • 1.2 Cheeses
    • 1.3 Opistosome
  • 2 Habitat and distribution
    • 2.1 Distribution
    • 2.2 Habitat
  • 3 Playback
  • 4 Nutrition
  • 5 Behavior
    • 5.1 Stridulation
  • 6 References

General characteristics

Solifuges can vary in their color and size depending on the species. In general, sizes can vary between 10 and 70 millimeters. The surface of its body is covered with sensory hairs and numerous spines..

Most species exhibit a uniform yellow, brown, or light brown color. Some species have a pattern of longitudinal black stripes on a yellowish background on the abdomen..

Solifuge body scheme By M. P. Parker [Public domain]

Prosoma

In camel spiders, the prosoma consists of eight segments containing the head, mouthparts, pedipalps, and legs..

The first three segments are fused, while the posterior segments of the cephalothorax remain separate and mobile. This gives solifuge a primitive appearance compared to the rest of the arachnids. The head has an arched dorsal surface that forms a kind of carapace (prodorso).

One pair of eyes are located on an ocular tubercle located in the center of the anterior axis, near the site of insertion of the chelicerae.

Among the chelicerae is the mouth, made up of the labrum, the hypopharynx and a pair of maxillae that extend to join the pedipalps. The labrum lies anteriorly between the chelicerae and forms the rostrum, a spike-shaped structure.

The first pair of legs is thinner than the rest and lacks nails at the distal end. These legs are used as sensory structures. The remaining three pairs of legs are ambulatory.

At the bases (coxas) and trochanter of the fourth pair are the racket organs or malleoli, which are characteristic sensory organs of this group of arachnids..

Cheliceros

One of the most outstanding characteristics of the order Solifugae is the size and shape of the chelicerae of these animals. These structures originate between the basal segments of the pedipalps and comprise two segments.

The second segment articulates with the base of the first segment, allowing the chelicerae to open and close dorsoventrally in a pincer fashion. The ventral segment is mobile, while the dorsal segment is fixed and larger.

These appendages are adapted to catch, immobilize and crush prey. Once they catch them, the chelicerae move in a saw shape, destroying the food and carrying it to the face..

Both segments are composed of ornaments and teeth that vary in shape and number according to the species. In females, chelicerae are larger and more ornate. In males, after the last molt, when they reach the adult stage, an organ called the flagellum develops in the dorsal segment of the chelicerae.

The function of this organ is still uncertain, although it is estimated that it may be related to the excretion and management of an exocrine secretion or have some role in territoriality during reproductive times..

Opistosome

The prosome joins the opistosome by a narrow pedicel with an internal diaphragm. The abdomen is made up of 10 or 11 segments, with the gonopore located in the first abdominal segment and surrounded by two plates that show slight differences between the sexes..

In the second and third abdominal segment, are the respiratory pores (stigmata) that connect internally to the tracheae (respiratory organs).

In most families of the order Solifugae, the anal opening is at the rear end of the abdomen. However, in the family Rhagodidae the anus is found in the ventral area of ​​the last segments.

All abdominal segments have a sclerotic plaque in the dorsal part (tergitos) and in the ventral part (sternites) and in the lateral part of each segment there is a soft membranous area (pleuriths).

These membranous areas also separate the segments and give the abdomen a certain degree of flexibility that allows them to expand during feeding and digestion..

Habitat and distribution

Distribution

Camel spiders have a wide distribution, being found both in the old world (Asia, Africa and Europe), with the exception of Australia and Madagascar, and in the new world (America).

Eight families are found in the Old World which are Ceromidae (Southern Africa), Galeodidae (Africa and West Asia), Gylippidae (Southern Africa and Southwest Asia), Hexisopodidae (Southern Africa), Karschiidae (North Africa, the Middle East and Asia ), Melanoblossiidae (Sub-Saharan Africa and Asia), Rhagodidae (Asia and Africa) and Solpugidae (Africa).

In the new world are the families Ammotrechidae (South America and Mesoamerica), Eremobatidae (North America) and Mummuciidae (South America). The Daesiidae family is found in the old and new world, with three genera in southern South America (Chile and Argentina) and several species in southern and southwestern Europe, Africa, and Asia..

Habitat

Camel spiders are practically restricted to arid, desert and semi-desert ecosystems. Despite this, some species have been recorded in rainforests or marginal areas.

In many species, animals build burrows or use depressions between rocks as shelters, staying in them for a few months, depending on the rainfall patterns of the place where they are. In this way, they avoid excessive loss of water in these environments..

Other species use less permanent shelters, in rock cavities or under decaying vegetation..

Reproduction

The reproduction of solifuges has been little studied, these studies being restricted to some families such as Galeodidae, Eremobatidae, and Solpugidae. Generally, the male makes contact with the female using his pedipalps.

If the male is accepted by the female, she acquires a quiescent behavior, although in some species the female takes an attacking posture. Once the male is accepted by the female, she uses her chelicerae to hold and position the female on the spermatophore..

In the Eremobatidae family, sperm transfer occurs directly in the female's genital operculum. The male opens said operculum with his chelicerae and introduces the seminal fluid, previously collected from his gonopore..

The females deposit their eggs in a shelter and in many cases it remains with them until the first molt of the juveniles. In other cases, the female leaves the nest when laying the eggs. Each egg mass contains between 50 and 200 eggs.

The stages of the life cycle of these animals include the eggs, post-embryos, from 8 to 10 nymph stages and the adult.

Males generally have a short-lived life. After reaching maturity, they do not feed or seek refuge because their only intention is to reproduce..

Macro view of solifuge chelicerae By RudiSteenkamp [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

Nutrition

All individuals of the order Solifugae are carnivores. These animals explore the environment in search of food and locate their prey using their pedipalps. Upon sensing a prey, it captures and fragments it using its powerful chelicerae.

Although most of their prey are cursory animals that prefer the ground, solifugos have been recorded climbing trees and walls stalking some prey. These climbing abilities are due to the fact that they have palpal structures called suctorial organs..

Although some species feed exclusively on termites, most camel spiders are generalist predators and can feed on other terrestrial arthropods and some vertebrates such as small lizards, snakes, and rodents..

Solifuges are important predators in arid environments with a high metabolism and a rapid growth rate. To cover these characteristics, they prey on any small animal that is within reach of their chelicerae. This explains the cannibalistic behavior that this order displays..

Among the arthropods that predate are also beetles, cockroaches, flies, grasshoppers, myriapods and scorpions.

Camel spiders are not poisonous, although the species Rhagodima nigrocincta it is the only one recorded with venom glands, which it apparently uses to paralyze its prey.

In the following video you can see how a camel spider attacks a millipede:

Behaviour

Camel spiders are gregarious during the post-embryo stage and the first nymph instar. However, after their first molt, individuals become very aggressive and it is common for them to become highly cannibalistic, so during this stage of development they leave the nest and become solitary..

Like many animals that live in arid areas, solifuges build burrows where they protect themselves from heat and desiccation. These shelters are generally built using their chelicerae, they can have a depth of between 10 and 20 cm and also cover the entrance with dry leaves..

These animals tend to have exploratory behaviors and are very active. Also, they are fierce fighters. In this way, individuals generally have several chain reactions when encountering another solifuge..

Some of these reactions are classified as immobility, alertness, mild threat (in which case the chelicerae move silently and balance on their legs) and serious threat (where the animal moves the chelicerae accompanying the movement with stridulations). This last reaction produces an attack or flight.

Stridulation

The stridulatory organs of solifuges are found in chelicerae and produce sound by rubbing against each other. These organs have the same morphology in both adults and juveniles and in both sexes. However, the intensity of the sound is proportional to the size of the animal.

Stridulations produce a wide frequency hissing sound, not audible to humans, with a maximum of 2.4 kHz. Although this characteristic has been very little studied in solifugees, some studies suggest that they have a defensive role in these animals..

Given that these animals do not have venom and also do not have defense mechanisms other than the use of chelicerae, they can constitute prey for other animals. It has been pointed out that they use stridulations as a way to imitate some animals with aposematic sounds, to avoid being predated.

This behavior is also related to a decrease in the cannibalistic tendencies of camel spiders..

References

  1. Cushing, P. E., Brookhart, J. O., Kleebe, H. J., Zito, G., & Payne, P. (2005). The suctorial organ of the Solifugae (Arachnida, Solifugae). Arthropod Structure & Development, 3. 4(4), 397-406.
  2. Goudsley-Thompson, J. L. (1977). Adaptational biology of solifugae (Solpugida). Bull. Br. Arachnol. Soc, 4(2), 61-71.
  3. Harvey, M. S. (2003). Catalog of the smaller arachnid orders of the world: Amblypygi, Uropygi, Schizomida, Palpigradi, Ricinulei and Solifugae. CSIRO publishing
  4. Hrušková-Martišová, M., Pekár, S., & Gromov, A. (2008). Analysis of the stridulation in solifuges (Arachnida: Solifugae). Journal of insect behavior, twenty-one(5), 440.
  5. Marshall, A. J., & Williams, W. D. (1985). Zoology. Invertebrates (Vol. 1). I reversed.
  6. Punzo, F. (2012). The biology of camel-spiders: Arachnida, Solifugae. Springer Science & Business Media.
  7. van der Meijden, A., Langer, F., Boistel, R., Vagovic, P., & Heethoff, M. (2012). Functional morphology and bite performance of raptorial chelicerae of camel spiders (Solifugae). Journal of experimental biology, 215(19), 3411-3418.

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