01 December, 2011

New information on the enigmatic cave scorpion Akrav from Israel

In 2006 cave explorers found the remains of a very unusual troglobitic scorpion in the Ayyalon Cave in Israel. Later, this scorpion was described as Akrav israchanani Levy, 2007 in a brand new family Akravidae.

Victor Fet, Michael Soleglad and Sergei Zonstein have now been able to examine available Akrav materials (it has been found 20 more or less complete specimens), and have published a detailed redescription and analysis of the species, genus and family.

Interestingly, no live specimens have been found. It also looks like all scorpions died at the same time, indicating a catastrophic extinction event in the cave environment. One theory is that there was a lethal H2S gas event. The scorpions found are not considered fossils, but at the present time it is not known if Akrav is an extinct taxa or not.

The paper has many detailed color pictures of the specimens found. The authors conclude that Akrav probably belongs to the family Superstitioniidae and that the Akravidae family status is not justified. No formal decisions on this matter are done in this paper, as this will be addressed in a forthcoming paper.

And what did Akrav eat in the closed, isolated caves with no large, terrestrial prey items? The authors suggest that the scorpion actually prey on the aquatic crustaceans that are also present in pools of water in the cave. The strange, beak-shaped fingers of the pedipalps seen in this scorpion may be a specialization for catching this kind of prey.

Akrav israchanani, a relict chactoid scorpion from the famous Ayyalon Cave in Israel, is analyzed for the first time since its original description by Gershom Levy (2007). All scorpions found in this cave (20 specimens) were dead, represented by exoskeletons; they are mostly fragmented during collection, many incomplete, but extremely well preserved, and have no evidence of fossilization. Time and cause of death are unknown. Diagnostic characters described by Levy are largely confirmed, and some are further clarified. An exhaustive set of microscopic images is published, encompassing data from all best preserved specimens. Previously unpublished morphological details are illustrated such as exact pattern of trichobothria, finger dentition, structure of pectinal organs, etc. Measurements of type series are provided. Presence of mites (Acari) in the Ayyalon Cave is not confirmed: the only specimen tentatively identified as a mite proved to be a late-stage scorpion embryo found inside one of the females; it is described and illustrated. Phylogenetic placement of Akrav within Recent scorpions is discussed, and its affinity to New World Chactoidea (Superstitioniidae: Typhlochactinae) is demonstrated. Biogeographic and ecological observations are provided. Unusual structure of pedipalp fingertips is suggested to be a device for foraging on aquatic crustaceans abundant in the cave’s pool.

Fet V, Soleglad ME, Zonstein SL. The genus Akrav Levy, 2007 (Scorpiones: Akravidae) revisited. Euscorpius. 2011(134):1-49. [Free fulltext]

Family Akravidae

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