Review of the genus Vibronychiurus ( Collembola : Onychiuridae ) , with a description of two new species

A new diagnosis of Vibronychiurus Pomorski, 1998 is given. V. archivari (Christiansen, 1956) comb. n. and V. hermonicus (Gruia, Poliakov & Broza, 2000) stat. & comb. n. are redescribed on the basis of the types and new specimens. Two new species are described: V. aestimabilis sp. n. from Khakasiya (Russia) and V. caucasicus sp. n. from Caucasus (Russia). A key to the species Vibronychiurus is provided.


INTRODUCTION
Thanks to the kindness of S. Stebaeva and Y. Sveenkova I have received two unidentified species of Vibronychiurus Pomorski, 1998, collected in Russia: South Siberia (Republic of Khakasiya) and the Caucasus.For comparison, I examined the types and other material of four species included in this genus, listed in the Checklist of Collembola [(http://www.geocities.com/~fransjanssens/taxa/onycinae.htm),updated on 2005.01.27].Examination of this material has convinced me that: 1.The Russian material represents two new species of Vibronychiurus.
2. Onychiurus obsiones Cassagnau, 1963 actually belongs to the genus Onychiurus Gervais, 1841 and should be removed from the list of Vibronychiurus, because it has a distal whorl on tibiotarsi with nine setae and furca reduced to a finely granulated area with 2+2 setulae in one row posteriorly.
4. The diagnosis of the genus should be expanded, as a consequence of the discovery of two new species, which are described here.
The present work contains in addition a determination key to all species of the genus.
The nomenclature of morphological details used in the descriptions was adopted after Pomorski (1998a) and Fjellberg (1999).
Diagnosis.Cylindrical onychiurids with slightly broadened region of abdominal segments III-IV, with or without anal spines.Granulation uniform and fine, with stronger granules around anterior cephalic pseudocelli and submedian pseudocelli on abdominal tergum V. Furca reduced to finely granulated area (divided in four parts as in Figs 16 and 20) with 1+1 setulae posteriorly, in contact with border between abdominal sterna III and IV.Sense organ of antennomere III with four or five papillae and smooth, straight sensory clubs.Vesicles in postantennal organ granulated.Labial palp A type.Dorsal chaetotaxy differentiated into apically rounded macro-and mesosetae and apically pointed microsetae.Sensilla on body indistinct.1+1 microsensilla on thoracic terga II-III always present.Seta d0 on head present.Distal whorl on tibiotarsi with eleven setae.When present, male ventral organ located at ventral tube.
Remarks.The genus Vibronychiurus was established by Pomorski (1998b), based on Vibronychiurus vinolentus Pomorski, 1998 from Bulgaria and Turkey.A repeated examination of the type species revealed an error in the original diagnosis of the genus.The figure of labium had been drawn based on the right labial palp of the holotype, with broken papilla C. The left labial palp of the holotype and palpi of all the paratypes are of A type.
The genus Vibronychiurus belongs to the group of genera of Onychiurini with eleven setae in distal whorl of tibiotarsi.The genus shares two characters with Onychiuroides Bagnall, 1948 andDeharvengiurus Weiner, 1996: the same structure of labium and a similar structure of the remnant of furca.It differs from them in the presence of only two posterior cephalic pseudocelli.Onychiuroides and Deharvengiurus have at least three pseudocelli, always arranged in a triangle.
Remarks.The type material is strongly crumpled and for this reason the parapseudocelli are impossible to recognise.
The species is very closely related with V. vinolentus, from which it differs only in the absence of male ventral organ.Unreproductive males of V. archivari have no trace of differentiated setae on ventral tube.

Vibronychiurus aestimabilis sp. n.
Diagnosis.V. aestimabilis sp.n. shares the presence of anal spines with V. archivari and V. vinolentus.The new species differs from both of them in its pseudocellar formula, the number of papillae in sense organ of antennomere III and a frequent presence of a denticle on the claw.V. aestimabilis has 3+3 pseudocelli on thoracic terga II and III and five papillae in sense organ of antennomere III.The claws of V. archivari and V. vinolentus are always toothless, and they have 2+2 pseudocelli on thoracic terga II and III and only four papillae in sense organ of antennomere III.
Etymology.The species name is derived from the Latin word "aestimabilis" -respectable, venerable.The species is dedicated to the eminent collembologist Sofiya K. Stebaeva, who kindly gave me the material for investigation.

Vibronychiurus caucasicus sp. n.
Diagnosis.V. caucasicus sp.n. shares the absence of anal spines with V. hermonicus, from which it differs in fine structural details of the postantennal organ and in the claw structure.Postantennal organ of V. caucasicus consists of 10-11 vesicles and their bases are oval and separated from each other, while the organ of V. hermonicus consists of 10-14 vesicles with almost circular bases, sometimes in contact with each other.Claws of V. caucasicus are always toothless, claws of V. hermonicus have a small ventral denticle.
housed in the Department of Biodiversity and Evolutionary Taxonomy, Wroc aw University).
Etymology.The species is named after its locality -the Caucasus Mts.
Material examined.One adult male, two subadult male, two juveniles, 16 II 1999, Israel, Mount Carmel, Lower Nahal Oren, North slope, under Quercus caliprinos tree, litter + soil, leg.T. Pavlicek (housed in the Department of Biodiversity and Evolutionary Taxonomy, Wroc aw University).
Remarks.So far I have been unable to examine the types of V. hermonicus, but five available specimens collected in the type locality (Mt.Carmel, Israel) fully agree with the original description with two exceptions (which I believe may be inaccuracies of that description).The species has parapseudocelli on the ventral side of the body and no lateral denticles on claws.
V. hermonicus was described as a subspecies of Onychiurus obsiones Cassagnau, 1963 and included in the genus Orthonychiurus Stach, 1954.Examination of the type material of O. obsiones shows that it belongs to the genus Onychiurus Gervais, 1841, and there is no close relationship between the two species.Two important characters of V. hermonicus (presence of eleven setae in the distal tibiotarsal whorl and labial palp of A type) show that the species undoubtedly belongs to the genus Vibronychiurus and therefore is hereby elevated to the species rank.Corresponding characters of Orthonychiurus are the following: nine setae in the distal tibiotarsal whorl and labial palp of AB type.V. hermonicus is closely related with V. caucasicus sp.n. described above (see diagnosis of V. caucasicus).