Alloseius Mašán & Halliday, 2009

Mašán, Peter & Halliday, Bruce, 2010, Review of the European genera of Eviphididae (Acari: Mesostigmata) and the species occurring in Slovakia 2585, Zootaxa 2585, pp. 1-122 : 33-36

Genus Alloseius Mašán & Halliday

Alloseius Mašán & Halliday, 2009a: 48 . Type species Iphidosoma pratensis Karg, 1965 , by original designation. Diagnosis (adults). Dorsal idiosoma ( Figs 19, 21). Idiosoma subglobular, almost hemispherical, lemonshaped, with caudal projection bearing a pair of marginal setae in females, dorso-ventrally flattened and ovoid in males. In female, dorsal shield entire, flat, suboval, often slightly constricted medially, not completely covering dorsal idiosoma, well sclerotised and coarsely sculptured; with 30 pairs of setae; small medial protuberance bearing setae j6; anterior extension of the shield overlapping onto ventral surface beyond vertex, fused to anterior parts of peritrematal shields to form an arched ventral structure bearing short setae j1 and z1; dorsal area of shield with coarse punctate-reticulate sculptural pattern, bearing 28 pairs of needle-like setae. In male, dorsal shield suboval to ovoid, covering whole dorsal surface, smooth, with simple flat and regularly rounded vertex, and bearing 30 pairs of simple needle-like setae. Vertical setae j1 minute, columnar, apically rounded and with ventral position in female, or slightly thickened and acuminate in male. Paravertical setae z1 thin and needle-like, and positioned ventrally in both sexes. Soft integument in female with complicated sculpture on surface, with dense granulation and additional net-like pattern. Pore-like structures small and subcircular.

Ventral idiosoma ( Figs 20, 22, 23). Ventral shields well sclerotised and clearly defined. Presternal platelets absent. Female sternal shield smooth, bearing three pairs of setae and two pairs of pores; first pair of setae placed on small and flat tubercles; sternal shield and endopodal platelets II–III partly to completely fused; endopodals III–IV free in soft integument; metasternal platelets present, each bearing metasternal seta st4 and associated pore. Male sterno-genital shield with five pairs of setae and three pairs of pores; first pair of sternal pores slightly elongated, slit-like, oriented transversely (similar pores present also in deutonymphs). Epigynal shield relatively long and slender, widely rounded posteriorly, slightly constricted medially and acuminate anteriorly, with a pair of genital setae situated close to posterior margin; genital pores placed in soft integument. Post-genital or post-sternogenital sclerites present. Anal shield free, suboval to subcircular, with three circum-anal setae and well developed cribrum. Exopodal platelets IV present, narrow and curved; other exopodals absent. Peritrematal shields well developed, wider in male, anteriorly fused to ventral vertex in female; peritremes long, and with anterior ends reaching anterior margin of coxa I. Metapodal platelets present. Ventral integument of female with complicated ornamentation, consisting of granular striation combined with more coarse punctate-reticulate pattern. Dorsolateral and opisthogastric soft integument with standard number of ten pairs of setae in female and female deutonymph, or with eight pairs of setae in male and male deutonymph (excluding setae st5 also situated on soft integument in both deutonymphs).

Gnathosoma . Palptarsus without paired macroeupathidium. Cheliceral digits and segments more massive in males and deutonymphs ( Figs 31, 96) than in females ( Figs 29, 30); movable digit of chelicerae bidentate in female or unidentate in male and deutonymph; female fixed digit with unusual hyaline sheath-shaped lamina ( Figs 29, 30); male movable digit with short and simple spermatodactyl ( Fig. 96). Epistome trispinate, with elongated central projection and short lateral prongs ( Fig. 28); central projection medially spiniferous in males ( Fig. 97).

Legs. Setation of legs I-II-III-IV: coxae 2-2-2-1, trochanters 6-5-5-5, femora 13-11-6-6, genua 11-11-8-7, tibiae 11-10-7-7 ( Table 3). In female, pulvillus of legs II–IV with elongated and pointed lateral lobes, projecting beyond claws ( Fig. 25).

Notes on the genus. According to Mašán & Halliday (2009a), the differential diagnosis of the genus Alloseius was based on the combination of the following female characters: (1) dorsal shield setae j1 columnar, with rounded tips; (2) anterior dorsal shield expanded ventrally beyond the vertex, so setae j1 and z1 are positioned ventrally; (3) the peritrematal shields are fused with the expanded anterior margin of the dorsal shield to form an arch-shaped antero-ventral shield structure that embraces coxae I; (4) coarse punctate-reticulate sculpture on dorsal shield as well as on striated ventral integument; and (5) movable cheliceral digit bidentate, fixed digit with hyaline projection. These female character states may be now supplemented as follows: (1) idiosoma lemon-shaped and with caudal projection bearing a pair of setae (Jv5); (2) dorsal shield not covering whole dorsal surface, with medial protuberance; (3) anterior hyaline margin of epigynal shield acuminate; (4) pulvilli II–IV with elongated and pointed lateral lobes, projecting beyond claws; and (5) dorsolateral and opisthogastric soft integument with ten pairs of setae (but with eight pairs in males).

Alloseius is similar in some respects to Uroiphis . Both genera have an acuminate anterior margin on the epigynal shield in females, additional granulation of soft integument in females, well-developed sexual dimorphism in the form of the idiosoma and dorsal setae, and very robust cheliceral digits in males and deutonymphs. The heavy chelicera may be associated with the phoretic behaviour of the male and deutonymph in these genera. For a detailed comparison of these two genera see Table 4.

We have found an unusual and remarkable modification of the female tarsal pulvilli on legs II–IV in this genus. These pulvilli have the lateral lobes elongated, pointed, and projecting beyond the claws ( Fig. 25). The same modification can also be seen in females of the genera Crassicheles ( Fig. 53) and Neocrassicheles ( Fig. 111). This may be a morphological adaptation to life in very fresh or humid dung habitats, enabling movement in almost semiaquatic substrates that are found in these habitats. A slightly different but functionally similar adaptation occurs in some strongly hygrophilous Blattisociidae , namely Cheiroseius Berlese 1916a , Cheiroseiulus Evans & Baker 1991 and Platyseius Berlese 1916a , in which the pulvilli of tarsi II–IV have the paired paradactyli and median lobe in a form of large expanded and flattened projections ( Lindquist et al. 2009).

Only two species were included in this genus by Mašán & Halliday (2009a), namely Alloseius pratensis Karg 1965 from Germany, and Alloseius insolentis Ma 1997 from China. The previous Slovakian record of A. pratensis , under the original name Iphidosoma pratensis (by Mašán 1994b) proved to be a misidentification of Halolaspis hypedon . It is possible that Iphidosoma verrucosa Nikolsky 1990 should also be included in this genus (Nikolsky 1990a, 1990b).