VENTRAL SKELETON OF MALE OF IXODID TICKS OF THE SUBFAMILY AMBLYOMMINAE, ITS EVOLUTION AND ROLE FOR SUPERGENERIC TAXONOMY

A comparative study of the ventral skeleton of idiosoma of male of the subfamily Amblyomminae was carried out. Much prominence was given to the hind half of idiosoma: great diversity of the composition, shape, size and topography of integumentary hard elements. A comparative stud y of the topography of dorsoventral musculature attachment to the vent ral wall of idiosoma in its hind half was carried out, too. The struct ure of skeleton with the largest area and least differentiation should be considered most primitive; in this case all hard elements have no distinct species or group form and are attached rigidly to the extensi ble cuticle. Such structure is characteristic of Haemaphysalis (Alloce rea) inermis which has primary unpaired anal and paired postanal shiel ds occupying nearly the whole ventral surface of the hind half of idio soma (fig. 1, 1). This variant suggests the other ones characteristic of the subfamily Amblyomminae. Two types of evolutionary transformatio ns of hard ventral integuments of male have been revealed. One type re presents a successive process of skeleton reduction through disintegra tion of primary shields into numerous small ones and decrease of their sizes and number up to their complete disappearance (figs. 1, 2). Har d elements are preserved for the most long time on hind branches of th e genital groove. Continuous chains of bundles of dorsoventral muscula ture, running along hind branches of the genital groove, are attached to hard elements and reach the posterior end of idiosoma between scall ops II and III (fig. 5). In H. (Allocerea) inermis muscles are attache d to the primary paired postanal shields, and where a partial skeleton reduction took place - to derivatives of these shields. The shields o r their derivatives have no species or group form, are asymmetrical an d attached rigidly to extensible integuments; the number of derivative sclerites varies much. A complete reduction of the ventral skeleton m arks the top of this evolutionary trend. In this case the topography o f musculature attachment is preserved (fig. 5). During evolutionary tr ansformations of the other type the primary postanal shields along the line of hind branches of the genital groove broke into adanal and acc essory ones, and their medial and lateral divergence took place (figs. 3, 4). Later on, in some recent genera the skeleton underwent a parti al reduction at the expense of the decrease of the above shields in ar ea, or complete disappearance of the accessory ones (figs. 3, 2; 4-6). On the contrary, in the other genera the area of hard integuments enl arged on account of the growth or increase in the number or shields (f ig. 4). If the transformations are estimated by the character of hard integuments area, then their initial stage is close to the area in H. (Allocerea) inermis (figs. 3, 1, 3). But this type of transformations lacks a complete reduction of ventral skeleton. The topography of atta chment of the bundles of dorsoventral musculature to the ventral wall of idiosoma is characterized by the branching from the genital groove to adanal and accessory shields and the bundles do not reach marginal scallops (fig. 6). All the shields have a distinct species or group fo rm and number; the connection with extensible integuments is semimobil e. The two types evolutionary transformations of the ventral skeleton of idiosoma in male with characteristic topography of musculature atta chment enable us to place two tribes in the subfamily Amblyomminae Ban ks, 1907. The tribe Amblyommini Banks, 1907 includes the genera Haemap hysalis Koch, 1844, Amblyomma Koch, 1844, Aponomma Neum., 1899, Anomal ohimalaya Hoog., Kaser et Mitch., 1970, Dermacentor Koch, 1844, Rhipic entor Nutt. et Warb., 1908. The tribe Rhipicephalini Banks, 1907 inclu des the genera Rhipicephalus Koch, 1844, Hyalomma Koch, 1844, Cosmiomm a Schulze, 1919, Nosomma Schulze, 1919, Boophilus Cur., 1891, Margarop us Karsch., 1897.