Achaemenothrombiidae, Saboori & Wohltmann & Hakimitabar, 2010

Saboori, Alireza, Wohltmann, Andreas & Hakimitabar, Masoud, 2010, A new family of trombidioid mites (Acari: Prostigmata) from Iran, Zootaxa 2611 (1), pp. 16-30 : 17

Achaemenothrombiidae fam. nov.

( Figs. 1–19 )

Type species: Achaemenothrombium cyrusi sp. nov.

Diagnosis. Larva: Idiosoma with three dorsal scuta. Prodorsal scutum without lateral flaps. Anus without sclerites. Supracoxal setae present on coxae of leg I. Palpal femur and genu with 1 seta each. Numbers of setae on coxae I–III: 2-2-1, on femora 6-5-5. Ge II and III each with 3 normal setae. Tibia of each leg with 8 to 10 normal setae. Ti I with 4 or 8 solenidia, Ti II with 2 or 3 solenidia. Tarsi of each leg elongate and hypertrichous. Ta I with 1 or 2 famuli, 5 or 8 to 9 solenidia and 6 or more eupathidia. Ti II with 2 to 3 solenidia and 1 eupathidium and famulus. Tarsi I & II with two falciform claws and a claw-like empodium. Tarsus III with inner claw curved outside, shorter and slightly thickened.

Remarks. The presence of a scutellum, the absence of a solenidion on tibia III and the fusion of telo- and basifemora of legs I–III indicate a close relationship of the Achaemenothrombiidae to the four families of Trombidioidea, i.e. Trombidiidae , Podothrombiidae , Neothrombiidae and Microtrombidiidae (incl. Eutrombidiinae ) ( Table 3). However, no characters of Achaemenothrombium demonstrate a clear sister relationship, or allow inclusion into any of these families without unwarranted upheaval of one (or more) families. Few analyses of phylogenetic relationships within the Trombidoidea have been carried out, most of which included larval ectomorphology only ( Welbourn 1984, 1991, Zhang 1994, Wohltmann 2006, Makol 2007), and most of which were not successful to provide unambiguous support (=apomorphies) for their hypotheses ( Table 3). Achaemenothrombium shares just one of these convincing apomorphies; i.e. the presence of a scutellum. Of the other vague characters listed as support for a particular clade, Achaemenothrombium shares with Trombidiidae the presence of two setae on coxa II. However, two setae on coxa II are also present in Neothrombiidae and moreover some Trombidiina other than Trombidoidea. Presence of more than one solenidium on tarsus II as well as the presence of multiple eupathida on tarsus I are common features of Achaemenothrombium and Podothrombiidae . However, multiple eupathidia ventrally on tarsus I do also occur in some Johnstonianidae , the number of solenidia on tarsus II ranges from 0–3 in Podothrombium - strong indication of the low value of both characters for phylogenetic interpretations. Moreover, differences in leg setation, presence of a bifid odontus and presence of two setae on coxa II make a close relationship of Achaementhrombium with Podothrombiidae unlikely. With regard to both cases, Trombidiidae and Podothrombiidae , Achaemenothrombium lacks other apomorphies listed for the respective taxon.

With regard to palp and leg setation patterns, which are often used to define families, the particular setation pattern of Achaemenothrombium again does not allow an affiliation to any other family without contradictions ( Table 4). Of the 15 segments compared in Table 4, Achaemenothrombium has just six similarities with Microtrombidiidae , five each for Trombidiidae and Podothrombidiidae, and only two with Neothrombiidae . Unique leg and palp characters for Achaemenothrombium are Ti I–III with 8 or more N, Ti I with 4 or more solenidia and Ta I with 5 or more solenidia ( Tables 3, 4).

Figures

FIGURES 1–4. Achaemenothrombium cyrusi gen. et sp. nov. (larva). 1, idiosoma, dorsal view; 2, idiosoma, ventral view; 3, scutum; 4, scutellum I & II.