Amblypygi

Amblypygi
Temporal range: Upper Carboniferous–Recent
Heterophrynus, Ecuador
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Amblypygi
Thorell, 1883
Families

Amblypygi is an order of arachnid chelicerate arthropods also known as whip spiders and tailless whip scorpions (not to be confused with whip scorpions and vinegaroons that belong to the related order Thelyphonida). The name "amblypygid" means "blunt rump", a reference to a lack of the flagellum ("tail") that is otherwise seen in whip scorpions. They are harmless to humans.[1][2] Amblypygids possess no silk glands or venomous fangs. They rarely bite if threatened, but can grab fingers with their pedipalps, resulting in thorn-like puncture injury.

As of 2016, 5 families, 17 genera and around 155 species had been discovered and described.[3] They are found in tropical and subtropical regions worldwide. Some species are subterranean; all are nocturnal. Fossilized amblypygids have been found dating back to the Carboniferous period, such as Graeophonus.

Physical description

Detail of pedipalps
Parts of an amblypygid, from Pocock (1900)[4]

Amblypygids range from 5 to 70 centimetres (2.0 to 27.6 in) in legspan.[3][5] Their bodies are broad and highly flattened, with a solid carapace and a segmented abdomen. Most species have eight eyes; a pair of median eyes at the front of the carapace above the chelicerae and 2 smaller clusters of three eyes each further back on each side.

Amblypygids have raptorial pedipalps modified for grabbing and retaining prey, much like those of a mantis.[6] The first pair of legs act as sensory organs and are not used for walking. The sensory legs are very thin and elongate, have numerous sensory receptors, and can extend several times the length of body.[3]

Behaviour

Damon diadema mother carrying young

Amblypygids have eight legs, but use only six for walking, often in a crab-like, sideways fashion. The front pair are modified for use as antennae-like feelers, with many fine segments giving the appearance of a "whip". When a suitable prey is located with the antenniform legs, the amblypygid seizes its victim with the long spines on the grasping pedipalps, before masticating the captured prey with its central pincer-like chelicerae.

Comparing the front and back legs of an Amblypygid

Courtship involves the male depositing stalked spermatophores, which have one or more sperm masses at the tip, onto the ground, and using his pedipalps to guide the female over them.[7] She gathers the sperm and lays fertilized eggs into a sac carried under the abdomen. When the young hatch, they climb up onto the mother's back; any which fall off before their first moult will not survive.

Some species of amblypygids, particularly Phrynus marginemaculatus and Damon diadema, may be among the few examples of arachnids that exhibit social behavior. Research conducted at Cornell University suggests that mother amblypygids communicate with their young with her antenniform front leg, and the offspring reciprocate both with their mother and siblings. The ultimate function of this social behavior remains unknown. Amblypygids hold territories that they defend from other individuals.[8]

The amblypygid diet mostly consists of arthropod prey, but this opportunistic predator has also been observed feeding on vertebrates.[3] Before, during and after molting they generally do not feed. Like any other arachnid, an amblypygid will molt several times during its life.[3]

Genera

Damon johnstonii from West Africa

The following genera are recognised:[9][10]

Palaeoamblypygi Weygoldt, 1996
Paracharontidae Weygoldt, 1996
Euamblypygi Weygoldt, 1996
Charinidae Weygoldt, 1996
Neoamblypygi Weygoldt, 1996
Charontidae Simon, 1892
Unidistitarsata Engel & Grimaldi, 2014

family unspecified

  • †Kronocharon Engel & Grimaldi, 2014 (1 species, Cretaceous)
Phrynoidea Blanchard, 1852
Phrynichidae Simon, 1900
Phrynidae Blanchard, 1852
incertae sedis

References

  1. ↑ "Pedipalpi". The international wildlife encyclopedia. 1 (3 ed.). Tarrytown, NY: Marshall Cavendish. 2002. p. 1906. ISBN 0-7614-7267-3. Retrieved 2011-10-29.
  2. ↑ Takashima, Haruo (1950). "Notes on Amblypygi Found in Territories Adjacent to Japan". Pacific Science. 4 (4): 336–338. ISSN 0030-8870. hdl:10125/9019.
  3. 1 2 3 4 5 Chapin, KJ; Hebets, EA (2016). "Behavioral ecology of amblypygids". Journal of Arachnology. 44 (1): 1–14.
  4. ↑ R. I. Pocok (1900). Fauna of British India. Arachnida.
  5. ↑ http://www.amazon.com/Whip-Spiders-Morphology-Systematics-Chelicerata/dp/8788757463
  6. ↑ Robert D. Barnes (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 617–619. ISBN 0-03-056747-5.
  7. ↑ Peter Weygoldt (1999). "Spermatophores and the evolution of female genitalia in whip spiders (Chelicerata, Amblypygi)" (PDF). Journal of Arachnology. 27 (1): 103–116.
  8. ↑ Chapin KJ; Hill-Lindsay S (2015). "Territoriality evidenced by asymmetric intruder-holder motivation in an amblypygid". Behavioural Processes. 122: 110–115.
  9. ↑ Mark S. Harvey (2003). "Order Amblypygi". Catalogue of the smaller arachnid orders of the world: Amblypygi, Uropygi, Schizomida, Palpigradi, Ricinulei and Solifugae. CSIRO Publishing. pp. 3–58. ISBN 978-0-643-06805-6.
  10. ↑ Engel, M.S.; Grimaldi, D.A. (2014). "Whipspiders (Arachnida: Amblypygi) in amber from the Early Eocene and mid-Cretaceous, including maternal care". Novitates Paleoentomologicae. 9: 1–17.
  11. ↑ Dunlop, J.A.; Zhou, G.R.S.; Braddy, S.J. (2007). "The affinities of the Carboniferous whip spider Graeophonus anglicus Pocock, 1911 (Arachnida:Amblypygi)". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 98: 165–178. doi:10.1017/S1755691007006159.

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