Scanning electron microscopy and morphometrics of nymph and larva of the tick Hyalomma impressum (Acari: Ixodidae).

Nymphs and larvae of ixodid ticks play an important role on the distribution of ticks and transmission of pathogens. They almost infest small mammals and birds which either move from place to place as rodents or migrate across different countries as migratory birds. The morphological descriptions of nymph and larva of the tick Hyalomma impressum were firstly studied in details by scanning electron microscopy and morphometric analysis. The distinguished characters of H. impressum nymph are as follows: dorsal idiosoma (excluding scutum) with 26-27 pairs of setae, posterior margin of scutum is narrowly rounded, posterolateral margins of scutum is straight, cervical grooves on the scutum extend to the midlength, coxa I with two large spurs, coxae (II-IV) with one small spur for each, spiracle is an egg shape with a numerous pores, palpus does not project beyond the hypostome, with nine setae dorsally and six setae ventrally, hypostome has cylindrical shape, dental formula 2/2, teeth number per file is eight in the outer file and seven in the inner file, basis capitulum has triangular shape without setae dorsally and tetragonal shape with three pairs of setae ventrally. The distinctive characters of H. impressum larva are as follows: idiosoma with 13 pairs of setae for each dorsal (including scutal setae) and ventral (excluding coxal setae), scutum with cervical grooves is narrow and shallow extending about one third of the scutal length, posterior margin of scutum is broadly rounded, posterolateral margins of scutum is straight, fold-like indistinctive spurs on coxae II and III, palpus with eight setae dorsally, three setae ventrally and one seta apically, hypostome with dental formula 2/2, teeth number per file (excluding small basal and apical teeth) is seven in the outer file and six in the inner file, basis capitulum without setae dorsally and with three pairs of setae ventrally.