Hormurus polisorum

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Hormurus polisorum
Systematics
Sub-stem : Jawbearers (Chelicerata)
Class : Arachnids (arachnida)
Order : Scorpions (Scorpiones)
Family : Hormuridae
Genre : Hormurus
Type : Hormurus polisorum
Scientific name
Hormurus polisorum
( Volschenk , Locket & Harvey , 2001)

Hormurus polisorum is a scorpion from the family Hormuridae that livesin limestone caves on Christmas Island .

description

Hormurus polisorum is a small scorpion with a reddish-brown body color that becomes noticeably paler towards the edges. The body is severely flattened. The carapace is 8.4 millimeters long in the male and 5.7 millimeters in the female. It is covered with numerous very small granules that do not form a pattern. The sternum is pentagonal with a smooth, shiny surface. Its color is a light brown in the front area, which merges into a pale yellow towards the rear. The combs of the comb organ have eight teeth in the male and six teeth in the female. The metasoma is short, slender, and yellowish-cream in color. The telson is longer than the fifth segment of the metasoma and has an extremely large poisonous bladder. The poison sting is short, strongly curved and dark brown.

Like many other cave invertebrates - including the troglobiont scorpions - Hormurus polisorum exhibits morphological adaptations to its habitat. The median pair of eyes is greatly reduced, the left ocellus is completely absent and the right is only present as an unpigmented hint. The lateral ocelli are reduced to a maximum diameter of 0.06 millimeters. The left lateral ocelli group has only two ocelli, the right three. The pedipalps with the chelae are significantly elongated. The body surface is hardly pigmented.

distribution

Hormurus polisorum is endemic to Christmas Island. Lives there with Liocheles australasiae a kind of closely related species Liocheles in surface scattering layers . It has been speculated whether Hormurus polisorium evolved from this species or whether it is the sister taxon of an extinct or as yet undiscovered aboveground species. Recent studies provide Hormurus polisorum and in southeastern Guinea widespread Hormurus karschii than be sister to a clade. This supports the assumption that both species or their common ancestor reached the habitats from the Australian plate across the ocean.

habitat

The terra typica of Hormurus polisorum are two limestone caves about 15 kilometers apart on Christmas Island . The holotype comes from the first main chamber of the Bishops Cave (CI-8) , about 120 meters from the cave entrance ( 10 ° 27 ′ 59.4 ″  S , 105 ° 35 ′ 30 ″  E ). The paratype was found in the dark zone of the 19th Hole or CI-19 cave ( 10 ° 25 ′ 2.4 ″  S , 105 ° 42 ′ 0 ″  E ). By 2014, scorpions could be found in two other caves, CI-10 and CI-103, on Christmas Island . The caves are located in the east, west and south of the island, so that Hormurus polisorum appears to be widespread but still rare.

Christmas Island is located in the Indian Ocean , about 2,600 kilometers west of Australia and 360 kilometers south of the Indonesian main island Java . It has an area of ​​about 135 square kilometers and has a tropical climate with a rainy season from December to April. Although the island is of volcanic origin, a large part of it consists of limestone . It has numerous caves in the limestone, of which those on the same plateaus are probably connected to each other. Until 1995 it was not known that there was a specialized cave fauna on Christmas Island. A specimen of Hormurus polisorum collected by a speleologist in 1987 was only known to zoologists in 1996. The discovery led to a systematic investigation of 23 of the 42 known caves on Christmas Island in 1998. A second specimen was caught.

The caves where Hormurus polisorum was found are among the at least 14 caves on the island where anchialine biotopes have developed. All of these caves have temperatures between 25.9 and 26.1 degrees Celsius and humidity between 96.6 and 98.4 percent. The caves are sensitive to the absence of the northwest monsoons , as can be caused by the El Niño phenomenon. The absence of monsoon rains leads to a partial drying out of the cave floors.

Way of life

The extensive morphological adaptations of Hormurus polisorum show that the species is a real troglobiont .

Hazard and protection

Hormurus polisorum is considered rare and it inhabits a highly specialized habitat in a very small range. This means that there is a constant threat from natural disasters and other influences. Anchialine ecosystems such as the caves in which Hormurus polisorum has been found are considered to be sensitive to the introduction of even minor organic pollution. Further threats are deforestation of the surface with the consequence of a changed water balance, the depletion of mineral resources, invasive species and human visitors.

Intensive efforts are being made worldwide to protect comparable caves. 68 percent of the area of ​​Christmas Island is protected as a national park . For the national park and its caves, including the Bishops Cave is Parks Australia North responsible. The agency is subordinate to the Australian Department for Environment and Energy. The local administration is responsible for the caves located outside the national park, including CI-19 .

Systematics

The systematic position of the genus Hormurus and its species has been subject to repeated changes in the past. Hormurus was synonymous with the genus Liocheles by Ferdinand Karsch in 1880 . At the level of families and subfamilies, there were repeated changes in the names and taxonomic ranks of individual taxa at the turn of the 20th to the 21st century. It was not until 2014 that arachnologists Lionel Monod and Lorenzo Prendini were able to reorganize and reinstate the genera Hormurus and Hormiops on the basis of extensive data on the phylogenetics , morphology and biogeography of all species of the Liocheles genus . Currently, the genus is Hormurus with ten other genera in the subfamily brought by the family Hormuridae .

The distribution of the genus Hormurus now almost completely takes into account biogeographical regions. After Monod's and Prendini's reorganization, Hormurus polisorum is the only representative of its genus that occurs west of the Wallace line modified by Huxley . The Liocheles australasiae , which also occurs on Christmas Island and is extremely widespread for a scorpion, is the only species of the genera Liocheles and Hormiops that is also widespread east of this line.

Initial description

The first description was as Liocheles polisorum in 2001 by the arachnologists Erich S. Volschenk , N. Adam Locket and Mark S. Harvey after two specimens collected in different caves on Christmas Island.

Type material

In 1987 all known caves on Christmas Island were examined as part of a speleological expedition. The holotype of Hormurus polisorum was discovered in the Bishops Cave . The male specimen was sent to the Western Australian Museum in Perth but was incorrectly delivered. It was not found until 1996 in a Perth hospital. The paratype is a female animal collected in 1998 during an inventory of the cave fauna of Christmas Island. The type material is in the collection of the Western Australian Museum in Perth.

etymology

The species name honors the American arachnologist Gary A. Polis, who died in 2000, and specifically his entire family, who gave each other support, encouragement and inspiration in their work and goals.

Synonyms

  • Liocheles polisorum Volschenk , Locket , Harvey , 2001 : the genus Hormurus was already in 1880 by Ferdinand Karsch with Liocheles been synonymised so Liocheles at the time of the first description of polisorum Hormurus the correct genus name was. The genus Hormurus was reinstated by Monod and Prendini in 2014, making Liocheles polisorum a synonym.

literature

Individual evidence

  1. ↑ a b c d Erich S. Volschenk, N. Adam Locket and Mark S. Harvey: First record of a troglobitic Ischnurid scorpion from Australasia, p. 163.
  2. ↑ Erich S. Volschenk, N. Adam Locket and Mark S. Harvey: First record of a troglobitic Ischnurid scorpion from Australasia, p. 164.
  3. ↑ a b Erich S. Volschenk, N. Adam Locket and Mark S. Harvey: First record of a troglobitic Ischnurid scorpion from Australasia, p. 169.
  4. ↑ a b c d Erich S. Volschenk, N. Adam Locket and Mark S. Harvey: First record of a troglobitic Ischnurid scorpion from Australasia, p. 161.
  5. ^ Lionel Monod and Lorenzo Prendini: Evidence for Eurogondwana, p. 91.
  6. ^ William F. Humphreys: Subterranean fauna of Christmas Island: habitats and salient features, p. 38.
  7. ^ William F. Humphreys and Stefan M. Eberhard: Subterranean Fauna of Christmas Island, p. 59.
  8. ^ A b Paul D. Meek: The History of Christmas Island and the Management of its Karst Features, p. 31.
  9. ^ William F. Humphreys and Stefan M. Eberhard: Subterranean Fauna of Christmas Island, p. 60.
  10. ^ A b c William F. Humphreys and Stefan M. Eberhard: Subterranean Fauna of Christmas Island, p. 64.
  11. ^ William F. Humphreys and Stefan M. Eberhard: Subterranean Fauna of Christmas Island, p. 66.
  12. ↑ Paul D. Meek: The History of Christmas Island and the Management of its Karst Features, pp. 32-33.
  13. ^ A b Paul D. Meek: The History of Christmas Island and the Management of its Karst Features, p. 34.
  14. ↑ a b c Lionel Monod and Lorenzo Prendini: Evidence for Eurogondwana, pp. 71–73.
  15. ↑ Lionel Monod and Lorenzo Prendini: Evidence for Eurogondwana, pp. 85–86.
  16. ↑ Lionel Monod and Lorenzo Prendini: Evidence for Eurogondwana, pp. 93–96.