Sertitympanum Elsen & Whitaker, 1985

Masan, Peter, 2017, A revision of the family Ameroseiidae (Acari, Mesostigmata), with some data on Slovak fauna, ZooKeys 704, pp. 1-228 : 1

Genus Sertitympanum Elsen & Whitaker, 1985

Sertitympanum Elsen & Whitaker, 1985: 119. Type species: Sertitympanum separationis Elsen & Whitaker, 1985, by original designation.

Diagnosis (adults).

Dorsal shield variously sclerotised and ornamented, with 28-29 pairs of setae, including z6; setae Z2 absent in some species. Dorsal shield setae similar in adults of both sexes, relatively short (with tips never reaching bases of the following setae of the same longitudinal rows), mostly smooth and spatulate, sometimes crenelated, paddle-shaped or spoon-shaped, with a broad flat end tapering to the base; setae j1 otherwise modified, smooth or serrate, usually with pointed apex, and often with ventral position on vertex. In female, st1 and st2 on sternal shield, st3 on small suboval or subtriangular pseudo-metasternal platelets, and st4 on soft integument; endopodal platelets II-III well developed, relatively large, subtriangular and close to posterolateral angles of sternal shield; anterior margin of epigynal shield usually deeply concave to form two cusps, genital poroids on soft integument. Opisthogastric region with five pairs of setae in females and males (JV1-JV3, JV5, ZV2; JV4 absent); setae JV5 usually similar to those on dorsal shield, other ventrally inserted setae simple, smooth and needle-like; females with three pairs of opisthogastric setae (JV1, JV5, ZV2) on soft integument and two pairs (JV2, JV3) on ventrianal shield; male with more expanded ventrianal shield bearing all five pairs of opisthogastric setae. Peritrematal shields anteriorly fused to dorsal shield, with enlarged cavity-like poroid structure at the level of coxa III and well developed parapodal portion. Metapodal platelets relatively large, longitudinally elongate. Soft striate integument simple, not with additional sclerotic granulation. Corniculi normally sclerotised, well spaced and trifid; setae h1 markedly thickened proximally, curved and abruptly tapered medially, attenuate distally, and sharply pointed apically. Fixed digit of chelicera with three subequal teeth on proximal masticatory area; male spermatodactyl small, shorter than movable cheliceral digit. Epistome with anterior margin produced into narrow and bifid central projection; lateral margins with several minute spines. Palptarsal apotele two-tined. Coxae I-IV with rows of minute spines, coxae II with spine-like process on anterior surface; coxae I-IV and femora I-IV with lamellar and/or papular sclerotic structures. Genu III, and tibiae III-IV with two anterolateral and two posterolateral setae. Tarsi I-IV each with empodium and rudimentary claws, or claws absent. Insemination apparatus with papilla-like sperm induction pores (solenostomes) associated with inner margin of coxae III; spermathecal ducts free and elongated.

Remarks.

Elsen and Whitaker (1985) proposed the genus Sertitympanum to accommodate three species based on females and found in North America, the type species Sertitympanum separationis , as well as Sertitympanum exarmatum and Sertitympanum contiguum . They characterised this genus by the presence of leg excrescences, peculiar cog-wheel-like sculpture on sternal shield and presence of a pair of large ventrolateral lenticular metapodal platelets (and by many other characters). These characters were considered by them to be the most important and distinct for their newly established genus, although they can be detected also in the other ameroseiid species, especially in the genus Kleemannia (for example, rounded and well scalloped circular structure on the sternal shield can be found in Kleemannia plumosa ).

The two further species of the genus, described from the North Africa (Egypt) by Nasr and Abou-Awad (1986), are lacking the cog-wheel-like sculptural pattern on the sternal shield, but despite this and slightly different appearance they are congeneric with the species from the American continent in many character states as follows: (1) form of dorsal shield setae; (2) dorsal chaetotaxy (z6 present and Z2 absent, as in Sertitympanum separationis ); (3) general arrangement of ventral shields; (4) bicuspid anterior margin of epigynal shield; (5) chaetotaxy of opisthogastric soft integument and ventrianal shield; (6) presence of cavity-like poroid structure on peritrematal shield; (7) presence of papilla-like sperm induction pores close to coxae III; (8) sclerotic sculpture and chaetotaxy of legs; (9) reduction of tarsal claws in legs I-IV (not stated in an original description of the genus, but found in S. separationis in which the claws are fully reduced); (10) special form of h1; (11) dentation of chelicera; (12) trifid form of corniculi; (13) bifurcate form of epistome (not stated in an original description of the genus but found in S. separationis ); and (14) two-tined form of palptarsal apotele.

Sertitympanum is similar in some respects to Kleemannia . Both genera have the same leg chaetotaxy, two pairs of opisthogastric setae on ventrianal shield, and arrangement and shape of some ventral shields. As a result of this similarity and the absence of a cog-wheel-like sculpture on sternal shield in some species, three Sertitympanum species were initally described in Kleemannia ( Sertitympanum bassolsae , Sertitympanum nodosum and Sertitympanum zaheri ) and classified in this genus up to now. Sertitympanum can be distinguished from Kleemannia by the following characters: (1) dentation of fixed cheliceral digit (three teeth in Sertitympanum , four in Kleemannia ); (2) structure of ambulacral apparatus (claws rudimentary or absent in Sertitympanum , claws normally developed in Kleemannia ); (3) form of central process of epistome (furcate in Sertitympanum , undivided in Kleemannia ); (4) form of h1 (thickened proximally, curved and attenuate medially, subfalcate in Sertitympanum ; thin or thickened, always straight and regularly tapered in Kleemannia ); (5) dorsal setation in forms with 28 pairs of dorsal shield setae (z6 present and Z2 absent in Sertitympanum , z6 absent and Z2 present in Kleemannia ); (6) length and form of dorsal setae (shorter, with their apices and bases well separated, leaf-shaped, oblanceolate, spatulate or obovate, with rounded apex in Sertitympanum ; longer, with their apices and bases adjacent or overlapping, tubiform or feather-shaped, with pointed apex in Kleemannia ).

There were five very similar species described to this time ( Sertitympanum aegyptiacum , Sertitympanum bassolsae , Sertitympanum nodosum , Sertitympanum palmatum and Sertitympanum zaheri ), with only simple reticulation on the sternal shield, although some curved sculptural lines, and perhaps also shallow depression, are present and better defined. Sertitympanum nodosum was introduced first (Sheals, 1962), based only on a single specimen, a weakly sclerotised and medially distorted female, found in Argentina. Unfortunately, the followers overlooked the existence of S. nodosum in a differential diagnosis to their new species ( El-Badry et al. 1979, Nasr and Abou-Awad 1986, Vargas and Polaco 2001).

Sertitympanum needs a thorough revision, and it comprises eight species considered here to be valid, most of which are widespread in nests of small mammals (species from North America), soil detritus and litter (species from Egypt). In Iran, Sertitympanum aegyptiacum is reported from honey bee hives, stored rice, rice dust and debris, and soil of vineyards ( Kazemi and Rajaei 2013). The genus Sertitympanum is here firstly recorded from Europe (see remarks in Sertitympanum nodosum ).