Centipede

From Wikipedia, the free encyclopedia

Centipedes
Image:Centipede.jpg
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Myriapoda Class: Chilopoda Latreille, 1817
Orders and Families
See text

Centipedes are terrestrial arthropods belonging to the class Chilopoda and the Subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. A key trait uniting this group is a pair of poison claws or forcipules formed from a modified first appendage. This also means that centipedes are an exclusively predatory taxa, which is uncommon.

Centipedes normally have a drab coloration combining shades of brown and red. Cavernicolous and subterranean species may lack pigmentation and many tropical Scolopendromorphs have bright aposematic colors. Size can range from a few millimeters in the smaller Lithobiomorphs and Geophilomorphs to about a foot in the largest Scolopendromorphs.

Worldwide there are estimated to be 8,000 species ^[1]. Currently there are about 3,000 described species. Geographically, centipedes have a wide range, which reaches beyond the Arctic Circle ^[2]. Centipedes are found in an array of terrestrial habitats from tropical rainforests to deserts. Within these habitats centipedes require a moist micro-habitat due to their rapid rates of water loss. Accordingly, they are found in soil and leaf litter, under stones and deadwood, and inside logs. In addition, centipedes are among the largest terrestrial invertebrate predators and often they contribute a significant proportion to invertebrate predatory biomass in terrestrial ecosystems.

Contents 1 Anatomy 2 Evolution 3 Life History 4 Ecology 5 Largest Centipede 6 Orders and families 7 List of some common species 8 Footnotes 9 References 10 Further reading 11 External links

[edit] Anatomy

Centipedes have elongated dorsal-ventrally flattened bodies with repeated segments (ranging from 15 to 191 pairs of legs) ^[3]. Each segment bears a single pair of legs and has a dorsal plate (tergite) and a ventral plate (sternite). Laterally each segment has a soft less scelerotized region known as the plueral membrane. This is where the spiracles for gas exchange are located in all orders except for the Scutigeromorpha (where they are located mid dorsally). The legs are segmented and segments are named proximal to distal: coxa, trachanter, prefemur, femur, tibia, and tarsus. Each leg terminates in a claw.

At the anterior end of the centipede is the head. Dorsally the head consists of a cephalic plate which is distinct in appearance from the tergites. Laterally on the head some centipedes have eyes. The order Geophilomorpha is blind. Scutigeromorphs have compound eyes and the other orders have no eyes or simple ocelli ranging from one pair to many. The ventral view of the head reveals the centipedes most prominent characteristic its poison claws or forcipules. There are also three pairs of mouthparts all derived from the modification of appendages. There is a mandible with a first maxillae ventral to it and a second maxillae ventral to the first. These mouthparts are used for both feeding and grooming. At the anterior of the head there is a pair of antennae which vary in length and number of segments (except for the Geophilomorpha where the # of segments is fixed at 14).

The posterior end of a centipede has a conspicuous pair of legs named the ultimate or anal legs. These legs are not used for walking and are usually morphologically distinct from other pairs. Instead, they are used for defense and mating and so they often are morphologically distinct between the sexes. Ultimate legs can be inflated, excessively spined, and or morphologically complex with crests and furrows. The sexual organs are also located on the posterior end of the centipede. Sexual organs are externally visible in Scutigeromorpha and Lithobiomorpha, and some Geophilomorpha whereby males and females are easily distinguished. Scolopendromorpha do not have externally visible sexual organs, which makes sexing difficult. Scolopendromorph females may be larger or wider than males. Precise determination of sex can be accomplished upon dissection or by gently applying pressure and warm water to the genital sternite of a specimen to cause the sexual organs to emerge externally.

It also notable that centipedes have distinct sensory structures. The Tomosvary organ in Lithobiomorphs and Scutigeromorphs is located just posterior to the position of the eyes. The organ appears externally as an ellipse and its function is largely unknown. It has been suggested that it is a pressure, light, or humidity sensor. There is some evidence that it functions as a pressure sensor to detect sounds ^[4]. There are mechanoreceptors in the form of spines or hairs covering the legs and antennae. Lithobiomorphs have coxal pores on the ventral surface of the coxae of legs 12-15 in adults. These pores are present in pore fields consisting of 3-4 rows of pores. They are suspected to function in both osmoregulation and pheremone release ^[5]. Pore fields are found on some Geophilomorph and Scolopendromorph species on various sternites and on the ultimate coxae. It is not certain if their function is similair across the orders.

[edit] Evolution

Centipedes have a fossil record dating back 420 million years to the late Silurian ^[6]. They belong to the subphylum Myriapoda which includes Diplopoda, Symphyla, and Paurapoda. The oldest fossil land animal is a myriapod. Arthropluera was a myriapod from the Carbiniferous that reached 8 feet in length. Within the myriapods centipedes are believed to be the first of the extant classes to branch from a common ancestor. There are five orders of centipede: Craterostigmomorpha, Geophilomorpha, Lithobiomorpha, Scolopendromorpha, and Scutigeromorpha. These orders are united into the monophyletic clade Chilopoda by the following synapomorphies: 1) first post-cephalic appendage modified to poison claws. 2) embryonic cuticle on second maxilliped has egg tooth. 3) the trochanter-prefemur joint is fixed. 4) a spiral ridge on the nucleus of spermatazoan ^[7]. Chilopoda is then split into two clades: the Notostigmomorpha including the Scutigeromorpha and the Pluerostigmomorpha including the other four orders. The main difference is that the Notostigmomorpha have their spiracles located mid-dorsally. It was previously believed that Chilopoda was split into Anamorpha including the Lithobiomorpha and the Scutigeromorpha, and Epimorpha including the Geophilomorpha and Scolopendromorpha based on developmental modes, with the relationship of Craterostigmomorpha being uncertain. Recent phylogenetic analyses using combined molecular and morphological characters supports the previous phylogeny ^[8]. The Epimorpha clade still exists as monophyletic within the Pleurostigmomorpha, but the Anamorpha clade is polyphyletic.

[edit] Life History

Centipede mating does not involve copulation. Males spin a small web onto which they deposit a spermatophore for the female to take up. Sometimes there is a courtship dance, and sometimes the males just leave them for the females to find. In temperate areas egg laying occurs in spring and summer but in subtropical and tropical areas there appears to be little seasonality to centipede breeding. It is also notable that there are a few known species of parthenogenetic centipedes^[9].

The Lithobiomorpha, and Scutigeromorpha lay their eggs singly in holes in the soil, the female fills the hole in on the egg and leaves it. Number of eggs laid ranges from about 10 to 50. Time of development of the embryo to hatching is highly variable and ma take from one to a few months. These two orders have an anamorphic mode of development. The young usually hatch with only 7 pairs of legs and gain the rest in successive moults. Scutigera coleoptera, the American house centipede, hatches with only 4 pairs of legs and in successive moults has 5, 7, 9, 11, 15, 15, 15 and 15 before becoming a sexually mature adult. Life stages with fewer than 15 pairs of legs are called larval stadia (~5 stages). After the full complement of legs is achieved, the now post-larval stadia (~ 5 stages) develop gonopods, sensory pores, more antennal segments, and more ocelli. Time of development to reproductive period is highly variable within and among species. For example, it can take 3 years for S. coleoptera to achieve adulthood, whereas under the right conditions Lithiobiomorph species may reach a reproductive period in 1 year. In addition, centipedes are relatively long-lived when compared to their insect cousins, for example: the European Lithobius forficatus can live for 5 or 6 years. The combination of a small number of eggs laid, long gestation period, and long time of development to reproduction has led authors to label Lithobiomorph centipedes as K-selected ^[10].

The orders Geophilomorpha and Scolopendromorpha have an epimorphic developmental mode. Young are born with the full complement of legs. Females of Geophilomorpha and Scolopendromorpha show far more parental care, the eggs 15 to 60 in number are laid in a nest in the soil or in rotten wood, the female stays with the eggs, guarding and licking them to protect them from fungi. The female in some species stays with the young after they have hatched, guarding them until they are ready to leave. If disturbed the females tend to either abandon the eggs or young or to eat them; abandoned eggs tend to fall prey to fungi rapidly, thus breeding is difficult to study in these species. Clutch sizes of Epimorpha range from 10 to about 100.

Little is known of the life history of Craterostigmomorpha.

[edit] Ecology

Centipedes are an exclusively predatory taxa. They are known as generalist predators which means that they have adapted to eat a variety of different available prey items, as opposed to specialists who are adapted to eat one prey item (or one group/taxa of prey). Centipedes are also known to be nocturnal. Studies on centipede activity rhythms confirm this, although there are a few observations of centipedes active during the day and one species Strigamia chinophila that seems to be diurnal. What centipedes actually eat is not well known, because of their cryptic lifestyle and thorough mastication of food. Laboratory feeding trials confirm that they will take most anything that is soft-bodied and in a reasonable size range. It is controversial whether or not earthworms provide the bulk of diets for Geophilomorphs. It seems intuitive, since geophilomorphs burrow through the soil and earthworm bodies would be easily pierced by their posion claws. Observations suggest that Geophilomorphs cannot subdue earthworms larger than themselves, and so smaller earthworms may be a substantial proportion of their diet ^[11]. Scolopendromorphs given their size are able to feed on vertebrates as well as invertebrates. They have been observed eating reptiles, amphibians, small mammals, and birds. Large Scolopendromorphs may be very powerful for their size. Recently, it was discovered that S. gigantea hangs from cave ceilings secured by its hind legs to catch bats in midflight ^[12]. A large proportion of Lithiobiomorph diet may come from Collembola. Little is know about Scutigeromorph or Craterostigmomorph diets. It is also worth mentioning that all centipedes are potential intraguild predators. There is evidence that centipedes and spiders may frequently prey on one another. Here is direct evidence: Scolopendromorph eats Tarantula.

Although centipedes are voracious predators, they are also sought as prey. They are eaten by a great many vetebrates and invetebrates. The african ant Amblypone pluto specializes on Geophilomorphs and the South African Cape Black-headed snake Aparallactus capensis mainly feeds on centipedes.

Centipedes are found in moist microhabitats. Water relations are an important aspect of their ecology, since they lose water rapidly in dry conditions. Water loss is a result of centipedes lacking a waxy covering of their exoskeleton and excreting waste nitrogen as ammonia, which requires extra water. Centipedes deal with water loss through a variety of adaptations. Geophilomorphs lose water less rapidly than Lithobiomorps even though they have a greater surface area to volume ratio. This may be explained by the fact that Geophilomorphs have a more heavily sclerotized plueral membrane. Spiracle shape, size and ability to constrict also have an influence on rate of water loss. In addition, it has been suggested that number and size of coxal pores may be variables affecting centipede water balance.

[edit] Largest Centipede

Scolopendra gigantea, also known as the Amazonian giant centipede, is the largest existing species of centipede in the world, reaching over 30 cm (12 inches) in length. It is known to eat bats, catching them in midflight, as well as rodents and spiders. The prehistoric Euphoberia was the largest known centipede, growing up to one metre (39 inches) in length.

There are rumors that state that the Galápagos Islands giant centipede (Scolopendra galapagoensis) can reach sizes of up to 60 cm (over 25 in), although these rumours may result from the rarity of the particular centipede. Captive Galapagos centipedes don't often exceed 20 cm (8 inches) in body length.[1]

[edit] Orders and families

Craterostigmomorpha Devonobiomorpha † Geophilomorpha Aphilodontidae Azygethidae Ballophilidae Dignathodontidae Eriphantidae Geophilidae Gonibregmatidae Himantariidae Linotaeniidae Macronicophilidae Mecistocephalidae Neogeophilidae Oryidaev Schendylidae Sogonidae Soniphilidae

Lithobiomorpha Henicopidae Lithobiidae Pterygotergidae Scolopendromorpha Cryptopidae Scolopendridae Scolopocryptopidae Scutigeromorpha Scutigeridae

[edit] List of some common species

• Arizona desert centipede
• Black centipede
• Burrowing centipede
• Chinese red-headed centipede
• Common centipede
• Common desert centipede
• Egyptian centipede
• Feather tail centipede
• Galápagos centipede
• Giant centipede (Ethmostigmus rubripes)
• Giant desert centipede
• Giant North American centipede
• Giant Sonoran centipede
• House centipede
• Megarian banded centipede
• Peruvian giant orange leg centipede (Scolopendra gigantea)
• Red feather tail centipede
• Red-headed centipede
• Stone centipede
• Sonoran desert centipede
• Tanzanian blue ringed centipede
• Vietnamese centipede

[edit] Footnotes

[edit] References

• Campbell, Neil A. (1996): Biology: Fourth Edition, Benjamin/Cummings Publishing, New York ISBN 0-8053-1957-3 p. 614
• Cloudsley-Thompson, J.L. (1968): Spiders, Scorpions, Centipedes and Mites. Pergamon Press; Oxford
• Eason, E. H., (1964): Centipedes of the British Isles. Frederick Warne

[edit] Further reading

• Edgecombe, G.D., Giribet, G. & Wheeler, W.C. (2002): Phylogeny of Henicopidae (Chilopoda: Lithobiomorpha): a combined analysis of morphology and five molecular loci. Systematic Entomology 27: 31-64. PDF

[edit] External links

• Debunking of some centipede myths, by American Tarantula Society
• Centipedes of Australia - On-line guide, key and virtual centipede head
• Tree of Life Project – Chilopoda
• What do you call a centipede?
• Pictures of many centipede species plus information
• Photos of Australian centipede - Scolopendra morsitans
• Japanese Gejigeji
• [2]cs:Stonožky

da:Skolopender de:Hundertfüßer es:Ciempiés eo:Centpieduloj fr:Chilopoda io:Skolopendro it:Scolopendra he:נדלים nl:Duizendpoten ja:ムカデ no:Skolopendere pl:Pareczniki pt:Quilópode ro:Chilopod ru:Губоногие simple:Centipede su:Babakaur fi:Juoksujalkaiset sv:Enkelfotingar tl:Alupihan th:ตะขาบ tr:Çiyanlar zh:蜈蚣