Centipede

Centipedes (from Latin prefix , "hundred", and , , "foot") are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of legs, e.g. 15 or 17 pairs of legs (30 or 34 legs) but never 16 pairs (32 legs). A key trait uniting this group is a pair of venom claws or "forcipules" formed from a modified first appendage. Centipedes are a predominantly carnivorous taxon.

Centipedes normally have a drab coloration combining shades of brown and red. Cavernicolous (cave-dwelling) and subterranean species may lack pigmentation and many tropical scolopendromorphs have bright aposematic colours. Size can range from a few millimetres in the smaller lithobiomorphs and geophilomorphs to about in the largest scolopendromorphs. Centipedes can be found in a wide variety of environments.

Worldwide there are estimated to be 8,000 species of centipede, of which 3,000 have been described. Centipedes have a wide geographical range, reaching beyond the Arctic Circle.

Centipedes possess a variable number of ocelli, which are sometimes clustered together to form true compound eyes. Even so, it appears that centipedes are only capable of discerning light and dark, and not of true vision. Indeed, many species lack eyes altogether. In some species the final pair of legs act as sense organs similar to antennae, but facing backwards. An unusual sense organ found in some groups are the organs of Tömösvary. These are located at the base of the antennae, and consist of a disc-like structure with a central pore surrounded by sensory cells. They are probably used for sensing vibrations, and may even provide a sense of hearing. Forcipules are not true mouthparts, although they are used in the capture of prey items, injecting venom and holding onto captured prey. Venom glands run through a tube almost to the tip of each forcipule. as well as rodents and spiders. The now extinct Euphoberia was the largest centipede, growing up to in length.

Life cycle

Centipede reproduction does not involve copulation. Males deposit a spermatophore for the female to take up. In one clade, this spermatophore is deposited in a web, and the male undertakes a courtship dance to encourage the female to engulf his sperm. In other cases, 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.

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 of their young or eat them; abandoned eggs tend to fall prey to fungi rapidly. Some species of Scolopendromorpha are matriphagic, meaning that the offspring eat their mother.

Little is known of the life history of Craterostigmomorpha.

Anamorphy vs. epimorphy

Centipedes grow their legs at different points in their development. In the primitive condition, exhibited by the L, Scutigeromorpha and Craterostigmomorpha, development is anamorphic. That is to say, more pairs of legs are grown between moults; for example, Scutigera coleoptrata, 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. All mature Lithobiomorph centipedes have 15 leg-bearing segments. Scolopendromorphs, given their size, are able to feed on vertebrates as well as invertebrates. They have been observed eating reptiles, amphibians, small mammals, bats and birds. Collembola may provide a large proportion of Lithiobiomorph diet. Little is known about Scutigeromorph or Craterostigmomorph diets. All centipedes are potential intraguild predators. Centipedes and spiders may frequently prey on one another. and the South African Cape black-headed snake Aparallactus capensis. Species of all orders excluding Craterostigmomorpha have adapted to caves. Centipede densities have been recorded as high as 600/m² and biomass as high as 500 mg/m² wet weight. Small geophilomorphs attain highest densities, followed by small Lithobiomorphs. Large Lithobiomorphs attain densities of 20/m². One study of scolopendromorphs records Scolopendra morsitans in a Nigerian savannah at a density of 0.16/m² and a biomass of 140 mg/m² wet weight.

Hazards to humans

Some species of centipede can be hazardous to humans because of their bite. Although a bite to an adult human is usually very painful and may cause severe swelling, chills, fever, and weakness, it is unlikely to be fatal. Bites can be dangerous to small children and those with allergies to bee stings. The bite of larger centipedes can induce anaphylactic shock in such people. Smaller centipedes usually do not puncture human skin.

Evolution

}} }} }} The upper three groups form the paraphyletic Anamorpha. The fossil record of centipedes extends back to , during the Late Silurian. They belong to the subphylum Myriapoda which includes Diplopoda, Symphyla, and Pauropoda. The oldest known fossil land animal, Pneumodesmus newmani, is a myriapod. Being among the earliest terrestrial animals, centipedes were one of the first to fill a fundamental niche as ground level generalist predators in detrital food webs. Today, centipedes are abundant and exist in many harsh habitats.

Within the myriapods, centipedes are believed to be the first of the extant classes to branch from the last common ancestor. There are five orders of centipedes: Craterostigmomorpha, Geophilomorpha, Lithobiomorpha, Scolopendromorpha, and Scutigeromorpha. These orders are united into the clade Chilopoda by the following synapomorphies:

# The first post-cephalic appendage is modified to poison claws. # The embryonic cuticle on second maxilliped has an egg tooth. # The trochanter–prefemur joint is fixed. # There is a spiral ridge on the nucleus of the spermatozoon.

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 (Lithobiomorpha and Scutigeromorpha) and Epimorpha (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.

Orders and families

Scutigeromorpha

The Scutigeromorpha are anamorphic, reaching 15 leg-bearing segments in length. They are very fast creatures, and able to withstand falling at great speed: they reach up to 15 body lengths per second when dropped, surviving the fall. They are the only centipede group to retain their original compound eyes, with which a crystalline layer analogous to that seen in chelicerates and insects can be observed. They also bear long and multi-segmented antennae. Adaptation to a burrowing lifestyle has led to the degeneration of compound eyes in other orders. This feature is of great use in phylogenetic analysis. The group is the sole representative of the Notostigmomorpha, defined by having a single spiracle opening at the posterior of each dorsal plate. The more derived groups bear a plurality of spiracular openings on their sides, and are termed the Pleurostigmomorpha. Some even have several unpaired spiracles that can be found along the mid-dorsal line and closer to their posterior section of tergites. There are three families: Psellioididae, Scutigeridae and Scutigerinidae.

Lithobiomorpha

The Lithobiomorpha represent the other main group of anamorphic centipedes; they also reach a mature length of 15 thoracic segments. This group has lost the compound eyes, and sometimes has no eyes altogether. Instead, its eyes have facets or groups of facets. Its spiracles are paired and can be found laterally. Every leg-bearing segment of this organism has a separate tergite. It also has relatively short antennae and legs. Two families are included, Henicopidae and Lithobiidae.

Craterostigmomorpha

The Craterostigmomorpha are the least diverse centipede clade, comprising only two extant species, both in the genus Ceratostigmus. Their geographic range is restricted to Tasmania and New Zealand. They have a distinct body plan; their anamorphosis comprises a single stage; they grow from 12 to 15 segments in their first moult. Their low diversity and intermediate position between the primitive Anamorphic centipedes and the derived Epimorpha has led to them being likened to the platypus.

Scolopendromorpha

The Scolopendromorpha comprise 21 or more segments with the same number of paired legs. Their antennae have 17 or more segments. Their eyes have at least 4 facets on each side. The order comprises the three families Cryptopidae, Scolopendridae and Scolopocryptopidae.

Geophilomorpha

The Geophilomorpha bear upwards of 27 leg-bearing segments. They are eyeless and blind, and bear spiracles on all leg-bearing segments – in contrast to other groups, who only bear them on their 3rd, 5th, 8th, 10th and 12th segments – a "mid-body break", accompanied by a change in tagmatic shape, occurring roughly at the interchange from odd to even segments. This group, at 1260 spp. the most diverse, also contains the largest and leggiest specimens at 29 or more pairs of legs. They also have 14–segmented antennae. The group includes four families: Mecistocephalidae, Neogeophilidade, Geophilidae and Linotaeniidae.

Selected species

. Trinidad, 1961]] {| class="wikitable sortable" |-bgcolor="#cccccc" |Scientific name || Common name |- |Alipes grandidieri || Feather tail centipede |- |Ethmostigmus trigonopodus || Blue ring centipede |- |Lithobius forficatus || Stone centipede |- |Pachymerium ferrugineum || Earth centipede |- |Scolopendra galapagoensis || Galápagos centipede |- |Scolopendra gigantea || Peruvian giant orange leg centipede |- |Scolopendra heros || Giant red-headed centipede |- |Scolopendra morsitans || Red-headed centipede |- |Scolopendra polymorpha || Giant Sonoran centipede |- |Scolopendra subspinipes || Vietnamese centipede |- |Scutigera coleoptrata || House centipede |}

See also

Centipedes of the Mazon Creek fossil beds

References

External links

Centipedes and how to care for them

Debunking of some centipede myths, American Tarantula Society

Centipedes of Australia

Chilopoda, Tree of Life Web Project

What do you call a centipede?

Scolopendra.be

Chilobase

Myriapoda.org

Tasmanian Centipedes

Millipedes and Centipedes, Kansas State University

Category:Myriapods