Akrav israchanani

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Akrav israchanani
Akrav israchanani, dried up shell at the location in the Ajalon cave

Akrav israchanani , dried up shell at the location in the Ajalon cave

Systematics
Sub-stem : Jawbearers (Chelicerata)
Class : Arachnids (arachnida)
Order : Scorpions (Scorpiones)
Family : Akravidae
Genre : Akrav
Type : Akrav israchanani
Scientific name of the  family
Akravidae
Levy, 2007
Scientific name of the  genus
Akrav
Levy, 2007
Scientific name of the  species
Akrav israchanani
Levy , 2007

Akrav israchanani is a species of scorpion probably extinct between 1960 and 1991and the only known species of the Akravidae. The only site of their remains is the Ajalon Cave, discovered in April 2006in Israel .

Ajalon cave, hall with the cave lake

Finding

In April 2006, the Ajalon Cave was discovered in a limestone quarry in Israel . Upon closer inspection of the cave, in addition to living invertebrate cave animals of various species, the hollowed-out exoskeletons of scorpions were found. They stuck to the rocks on the bank of a small cave lake, their sites corresponded to the assumed different water levels of the lake. The scorpions were photographed where they were found and carefully detached from the rocks.

features

The shells and body parts, some of which fell apart when they were detached from the rocks of the cave or at an earlier point in time, came from at least 20 different scorpions. Israel Naaman, who discovered and picked up the scorpions in the Ajalon Cave, named the number of 32 scorpions found in his master's thesis, completed in 2011. Despite the fragmentation, the shells of the animals were in good condition, which had largely retained the diagnostic features. This was attributed to the climatic conditions in the cave, which had a high content of hydrogen sulfide in the atmosphere with almost 100% humidity and high temperatures.

The found covers were the remains of brown, medium-sized and elongated scorpions with a body length of about 50 mm, freed from all soft tissues. The carapace has slightly raised edges, the sternum is pentagonal and longer than it is wide. The limbs of the metasoma are longer than wide and are furrowed on the underside. The animals have neither eyes nor recognizable dispositions for it. The scissor fingers of her pedipalps are long, thin and have conspicuously curved tips.

The chelicerae have no ventral serrules. The elongated chelae are provided along their entire length with lined up and partially overlapping groups of denticles. The fixed scissor finger carries the trichobothria ib and it , on the ventral side of the base of the scissors the trichobothria V 1 to V 4 are arranged in a straight row over the entire length. The ventral trichobothria V 1 to V 3 are present on the patella , and the femur bears the closely spaced dorsal trichobothria d and i . The trichobothria pattern of the scorpions thus corresponds to type C.

Systematics

First description and type material

The scientific description of the scorpions found was carried out in 2007 by the Israeli arachnologist Gershom Levy . Based on the morphology , Levy placed them in a new genus and species, Akrav israchanani . The generic name Akrav is the Hebrew word for "scorpion" already used in the Bible. The specific epithet is a combination of the first names of Israel Naaman, the discoverer of the scorpions, and Chanan Dimentman , an Israeli zoologist who has studied the cave's ecosystem intensively since its discovery. In addition, it refers to Israel as terra typica of the new kind.

The remains of all the scorpions found are in the collections of the Hebrew University of Jerusalem . The holotype has the inventory number “HUJsc. 2673 ”, six paratypes have the numbers 2674 to 2679. The specified type locality is the Ajalon Cave, Israel Naaman was given as April 2006 as the collector.

Family Akravidae

The scorpions widespread in Israel and known until 2006 belong to the families Buthidae and Scorpionidae . Due to clear morphological differences, the scorpions found in the Ajalon Cave could neither be classified in this nor in any of the other scorpion families described so far. So Levy placed them in the new family Akravidae, within the superfamily Chactoidea .

The combination of various taxonomic features was decisive for this decision:

  • Pedipalps with the trichobothria pattern of type C ( exclusion of the families Buthidae and Chaerilidae );
  • pentagonal sternum, longer than wide ( excluding the family Bothriuridae );
  • crescent-shaped breathing holes;
  • smooth fingers of the chelicerae, without serrated teeth on the ventral surface; the movable finger with only one subdistal denticle, the medial and basal denticle of the fixed finger separated from each other ( exclusion of the families Iuridae and Caraboctonidae );
  • Comb organs with fulcra and only a few large teeth;
  • no tibial spurs;
  • Basitarsi with prolateral and retrolateral spurs;
  • Tarsi with paired ventral setae, without a series of intervening spines
  • the fifth segment of the metasoma with a single central keel ( excluding the family Pseudochactidae with two kills );
  • the sting has no subacular tubercle .

Review of the findings in 2010

In 2010 and 2011, arachnologists Victor Fet , Michael E. Soleglad and Sergei L. Zonstein re-examined the material in the collection of the Hebrew University. Regarding the family characteristics, they found that, unlike the first description , Akrav israchanani only has the prolateral tarsal spur. Based on this discrepancy, inaccurate statements by Levy about the arrangement of the denticles on the chelae and on similarities with the New World family Superstitioniidae , the status of the family Akravidae was questioned. The genus Akrav should be placed as a subtribe in the family Superstitioniidae, subfamily Typhlochactinae. For the time being, however, the authors have refrained from formal synonymization and intend a comprehensive phylogenetic analysis of the Akravidae and related taxa. Despite the different classification of Akrav in existing families, several changes of taxonomically important characteristics and more precise information regarding body dimensions and anatomical details, Levy's first description was essentially confirmed.

In his first description, Levy mentioned the discovery of a " mite " in one of the exoskeletons and considered the possibility that the soft tissues of the scorpions had been consumed by mites. The exact examination of the animal identified by Levy as a "mite" revealed that it was without a doubt the 3.6 millimeter long embryo of a scorpion. Numerous small, dark attachments were found on the shells of the scorpions, especially on the inside, which are in no way related to the anatomy of the scorpions, but can easily be viewed as piles of small scavengers . In some cases, feeding traces were found on softer parts of the exoskeleton. From the fauna of the Ajalon cave, only springtails of the genus Troglopedetes, about one millimeter in length , are considered to be responsible.

ecology

Connection between different levels of the Ajalon cave

Troglobionte scorpions

Troglobionte scorpions are rare worldwide. In 1964, the zoologist Albert Vandel introduced Biospéology in his fundamental work . La Biologie des animaux cavernicoles states that there are no strictly cave-dwelling scorpions. It was not until the end of the 1960s that the first troglobiont scorpions were discovered in Mexican caves with Typhlochactas rhodesi and Typhlochactas reddelli . In 1985, 13 species were known and the number of species described has increased steadily since then. The distribution of troglobiont scorpions is largely limited to the tropics, with evidence coming from Mexico, Brazil, Ecuador, Indonesia, Malaysia and Christmas Island . A number of other scorpions found in caves are considered to be only troglophilic or trogloxic elements of the respective fauna.

Finding a type of cave-dwelling scorpion in Israel, outside the tropics, was therefore surprising. Together with the crustaceans in the cave, they were interpreted as relic fauna from the time of the tropical ocean Tethys . They see other attempts at explanation as part of an underground ecosystem that has developed independently. Finally, the possibility is considered that the scorpions did not evolve with the crustaceans, but rather colonized and trapped the cave at a later date.

habitat

Until it was uncovered, the Ajalon Cave formed an ecosystem that was isolated from the outside world , into which neither water nor organic material could penetrate from the surface because of the dozen meters thick limestone layer above. In addition to a number of passages, the cave consists of a large chamber with a lake in which there is salty groundwater with a high concentration of hydrogen sulfide . The Ajalon cave is located in the area of ​​the Ayalon Saline Anomaly , the water of the cave lake comes wholly or partly from thermal springs .

Typhlocaris ayyaloni , the largest living creature in the cave and potential prey

food

The Ajalon Cave's ecosystem is based on the biomass produced by large quantities of sulfur-oxidizing bacteria . Living populations of crustaceans , pseudoscorpions , fish and springtails were found in cave animals .

The isotope analysis of the scorpions showed a PDB value of about −0.36 ‰. Feeding soil organisms from a normal atmosphere would result in a value of −0.25 to −0.18 ‰, and the deviating values ​​indicate a feeding of organic matter from the cave.

A prominent anatomical feature of Akrav israchanani are the hook-shaped curved tips of the chelae , especially the fixed limb. When the scissors are closed, the tips reach past each other and the serrated edges of the scissors create a gap. This form of claws, which is unique for scorpions, was interpreted as a possible adaptation to catching aquatic crustaceans. The Typhlocaris ayyaloni crustaceans living in the cave lake appear to be suitable prey. A few scorpions are known to catch water lice or live amphibiously in the tidal zone, and the shells of Akrav israchanani have only been found in the immediate vicinity of the cave lake.

In this context, the chelicerae of was similar formations dysderidae the genus Dysdera noted that from lice feed. In some species, compared to other representatives of the genus, specific elongations of the chelicerae can be observed, which are associated with a specialization in certain prey animals and with a special strategy of prey capture.

die out

Chronological order

Scorpion of the species Euscorpius italicus under UV light

The examination of the found remains led to the conclusion that they were not fossils , but recently deceased and dried up animals. There were no remains of internal organs in the covers. Despite intensive searches, no living or recently deceased specimens of Akrav israchanani could be found in the Ajalon cave . However, it cannot be ruled out that there are other caves in the region that are isolated from the outside world and in which a population of the animals could have survived.

The good condition of the dead animals, especially the lack of decomposition of the chitin by bacteria or fungi due to the climatic conditions in the cave , made it difficult to determine the time of death. Many of the recovered animals were covered with a salt crust, for which both the high humidity and the flooding of the hulls due to fluctuating water levels in the cave lake are possible causes. No signs of the beginning of fossilization were found.

One of the earliest findings was the surviving fluorescence of the envelopes under ultraviolet radiation . This fluorescence is typical of scorpions and is often exploited when catching live scorpions. The still existing fluorescence does not allow a chronological classification of the finds. Scorpions in museum collections with an age of 150 to 200 years also fluoresce, while in fossils from the Carboniferous to Triassic 250 to 300 million years old, the body surfaces are chemically changed and no longer fluoresce.

Only research published in 2011 on the history of the origins of the Ajalon cave and anthropogenic changes in the groundwater level in the area of ​​the cave made it possible to limit the extinction of Akrav israchanani . As part of the investigations, the water levels of the Höhlensee cave were reconstructed since 1951. The location of the dead scorpions and a comparison with the reconstructed water levels in the cave made it possible to establish that Akrav israchanani became extinct between 1960 and 1991.

Suspected causes

The hulls found showed no signs of external injuries, as would be inevitable in a fight with a hunter. In addition, no traces of animals that the scorpions may have fallen victim to have been found in the cave. Other cave-dwelling scorpions are always at the top of the food chain in their ecosystems.

In the area of ​​the Ajalon Cave, a drop in the groundwater level of 13 meters due to the pumping out of the groundwater has been established since 1951. As a result, the area of ​​the cave lake fell from around 4,000 to around 400 square meters. The lower production of biomass due to the reduction of the habitat is seen as a possible reason for the extinction of the scorpion Akrav israchanani , which, with its position at the end of the food chain , was particularly affected by disturbances in the ecosystem.

Initially, no possible prey for the scorpions was found in the cave , so that in the first description a lack of food was seen as a possible cause of extinction. Against this is the lack of external injuries in the animals found. Scorpions show cannibalism when there is a lack of food , and at least some of the dead animals should have shown corresponding traces. The interpretation of the elongated and hook-shaped curved chelae as an adaptation to the catching of crustaceans from the cave lake is more recent and also speaks against the thesis of the loss of food sources.

The scorpions found in the Ajalon cave had different ages when they died, there were fully grown and younger animals, but no youth stages. Nevertheless, the finding of an embryo in one of the envelopes indicates a reproducing population. The overall situation in the cave speaks for the sudden death of the entire population, and not for an accumulation of empty shells over several generations. A possible catastrophic event would be the release of a large amount of hydrogen sulfide from the cave lake, which caused the death of the scorpions. The survival of other land-living arthropods can easily be justified by the fact that the population of the scorpions was numerically small and resided in the particularly endangered area of ​​the cave lake.

Web links

The publications by Victor Fet (2011)http: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fwww.science.marshall.edu%2Ffet%2Feuscorpius%2FFet_Priroda%25202013_10.pdf~GB%3D~IA%3D~MDZ%3D%0A~SZ% 3D ~ double-sided% 3D ~ LT% 3DVictor% 20Fet% 20% 282011% 29 ~ PUR% 3D (online PDF, 726 kB, Russian) and Victor Fet, Michael E. Soleglad, Sergei L. Zonstein (2013)http: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fwww.science.marshall.edu%2Ffet%2Feuscorpius%2Fp2011_134.pdf~GB%3D~IA%3D~MDZ%3D%0A~SZ%3D~ double-sided% 3D ~ LT% 3DVictor% 20Fet% 2C% 20Michael% 20E.% 20Soleglad% 2C% 20Sergei% 20L.% 20Zonstein% 20% 282013% 29 ~ PUR% 3D (online PDF, 12.9 MB, English) contain extensive image material.

literature

Individual evidence

  1. ↑ Israel Naaman: Karst System and Ecology of the Ayalon Cave, Israel , p. 1.
  2. ↑ a b Gershom Levy: The first troglobite scorpion from Israel and a new chactoid family (Arachnida: Scorpiones) , pp. 91-92.
  3. ↑ a b c Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , p. 4.
  4. ↑ Israel Naaman: Karst System and Ecology of the Ayalon Cave, Israel , p. 47.
  5. ↑ a b c d e Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , p. 5.
  6. ↑ a b c d e f g h Gershom Levy: The first troglobite scorpion from Israel and a new chactoid family (Arachnida: Scorpiones) , p. 92.
  7. ↑ a b Gershom Levy: The first troglobite scorpion from Israel and a new chactoid family (Arachnida: Scorpiones) , pp. 92-93.
  8. ↑ a b c Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , p. 8.
  9. ^ Gershom Levy: The first troglobite scorpion from Israel and a new chactoid family (Arachnida: Scorpiones) , p. 93.
  10. ^ John T. Hjelle: Anatomy and Morphology , p. 33.
  11. ^ Gershom Levy: The first troglobite scorpion from Israel and a new chactoid family (Arachnida: Scorpiones) , p. 94.
  12. ↑ a b Gershom Levy: The first troglobite scorpion from Israel and a new chactoid family (Arachnida: Scorpiones) , pp. 94-95.
  13. ^ František Kovařík: Illustrated catalog of scorpions. Part I , Clarion Productions, Prague 2009, p. 17.
  14. ↑ M. Nechama Ben-Eliahu, Daniel Golani: Haasiana. A biennial Newsletter of the National Natural History Collections of the Hebrew University , Number 6, 2012, pp. 89–90, Online PDF, 650 kBhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fnnhc.huji.ac.il%2Fwp-content%2Fuploads%2Fhasiana%2FHaasiana%25206%25202012.pdf~GB%3D~IA%3D~MDZ% 3D% 0A ~ SZ% 3D ~ double-sided% 3D ~ LT% 3DOnline% 20PDF% 2C% 20650% 26nbsp% 3BkB ~ PUR% 3D (accessed March 5, 2014).
  15. ↑ a b c d e Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , p. 7.
  16. ↑ a b Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , pp. 39-44.
  17. ↑ Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , pp. 30-33.
  18. ↑ Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , pp. 21-25.
  19. ^ A b Wilson R. Lourenço, Renner Luiz Cerqueira Baptista, Alessandro Ponce de Leão Giupponi: Troglobitic scorpions: a new genus and species from Brazil . In: Comptes Rendus Biologies , Volume 327, Number 12, 2004, pp. 1151–1156, here p. 1153, doi : 10.1016 / j.crvi.2004.09.001 , Online PDF, 300 kBhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fwww.museunacional.ufrj.br%2Fmndi%2FAracnologia%2Faracnopdfs%2FLourenco%2520et%2520al%25202004%2520Troglo.pdf~GB3D MDZ% ​​3D% 0A ~ SZ% 3D ~ double-sided% 3D ~ LT% 3DOnline% 20PDF% 2C% 20300% 26nbsp% 3BkB ~ PUR% 3D (accessed on March 5, 2014) .
  20. ↑ a b Božidar PM Ćurčić: Ayyalonia dimentmani ng, n. Sp. (Ayyaloniini n. Trib., Chthoniidae, Pseudoscorpiones) from a cave in Israel . In: Archives of Biological Sciences , Volume 60, Number 3, pp. 331-339, here p. 332, doi : 10.2298 / ABS0803331C .
  21. ↑ a b c d e Gershom Levy: The first troglobite scorpion from Israel and a new chactoid family (Arachnida: Scorpiones) , p. 91.
  22. ↑ Amos Frumkin, Haim Gvirtzman: Cross-formational rising groundwater at an artesian karstic basin: the Ayalon Saline Anomaly, Israel . In: Journal of Hydrology , Volume 318, 2006, pp. 316–333, here p. 331, doi : 10.1016 / j.jhydrol.2005.06.026 , Online PDF, 650 kBhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fgvirtzman.es.huji.ac.il%2F1024x768%2Fpublications%2Fpdf%2F2006-JHydrol-Amos.pdf~GB%3D~IA%3D~MDZ% 3D% 0A ~ SZ% 3D ~ double-sided% 3D ~ LT% 3DOnline% 20PDF% 2C% 20650% 26nbsp% 3BkB ~ PUR% 3D (accessed March 5, 2014).
  23. ↑ Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , p. 46.
  24. ↑ Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , pp. 33-34.
  25. ↑ a b c d Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , pp. 45-46.
  26. ↑ a b M. Řezáč, S. Pekár, Y. Lubin: How oniscophagous spiders overcome woodlouse armor . In: Journal of Zoology , Volume 275, 2008, pp. 64-71, here pp. 66-69, doi : 10.1111 / j.1469-7998.2007.00408.x .
  27. ↑ a b Gershom Levy: The first troglobite scorpion from Israel and a new chactoid family (Arachnida: Scorpiones) , p. 95.
  28. ↑ Douglas D. Gaffin et al .: Scorpion fluorescence and reaction to light . In: Animal Behavior , Volume 83, Number 2, 2012, pp. 429-436, here p. 429, doi : 10.1016 / j.anbehav.2011.11.014 .
  29. ↑ a b Israel Naaman: Karst system and ecology of the Ayalon cave, Israel , p. 71.
  30. ↑ Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , pp. 5-6.
  31. ↑ James R. Reddell: Spiders and related groups In: William B. White, David C. Culver (Eds.): Encyclopedia of Caves. Second Edition , Academic Press, Waltham, MA 2012, pp. 786-797, here p. 787, ISBN 978-0-12-383832-2 .
  32. ↑ Victor Fet: Заметки о скорпионах и скорпиологах (German: "Notes on Scorpions"). In: Природа (German: “Priroda” / “Natur”), number 10, 2013, pp. 52–58, ISSN  0032-874X , online PDF, 726 kBhttp: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fwww.science.marshall.edu%2Ffet%2Feuscorpius%2FFet_Priroda%25202013_10.pdf~GB%3D~IA%3D~MDZ%3D%0A~SZ% 3D ~ double-sided% 3D ~ LT% 3DOnline% 20PDF% 2C% 20726% 26nbsp% 3BkB ~ PUR% 3D (Russian, accessed on March 15, 2014), on p. 56 detailed photos of Akrav israchanani with the hook-shaped tips of the pliers.
  33. ↑ Israel Naaman: Karst System and Ecology of the Ayalon Cave, Israel , p. 3.
  34. ^ Francis Dov Por et al .: Animal life in the chemoautotrophic ecosystem of the hypogenic groundwater cave of Ayyalon (Israel) , p. 9.
  35. ↑ Israel Naaman, Chanan Dimentman, Amos Frumkin: Active Hypogene Speleogenesis in a Regional Karst Aquifer: Ayyalon Cave, Israel , pp. 73-74.
  36. ↑ Israel Naaman: Karst System and Ecology of the Ayalon Cave, Israel , pp. 70–71.
  37. ↑ Israel Naaman, Chanan Dimentman, Amos Frumkin: Active Hypogene Speleogenesis in a Regional Karst Aquifer: Ayyalon Cave, Israel , p. 74.
  38. ↑ Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , p. 6.
  39. ↑ a b c Victor Fet, Michael E. Soleglad, Sergei L. Zonstein: The Genus Akrav Levy, 2007 (Scorpiones: Akravidae) Revisited , pp. 6-7.