Parthenogenesis in Mites and Ticks (Arachnida: Acari)

SYNOPSIS. Parthenogenesis is discussed according to type (arrhenotoky, thelytoky, deuteroLoky, artificial parthenogenesis, gynogenesis) and presence in various acarine taxa. Evidence for parthenogenesis is based on rearing and/or cytological studies. Arrhenotoky occurs in Mesostigmata, Prostigmata and Astigmata and usually does not occur sporadically throughout these taxa; when present it operates in many closely related species as the major type of reproduction in certain genera, subfamilies or families. Thelytoky is present in Mesostigmata, Metastigmata, Prostigmata, Astigmata and Cryptostigmata, but in no case is the major mode of reproduction in higher taxa, i.e. subfamilies, families. Its sporadic occurrence may or may not be accompanied by polyploidy. Deuterotoky occurs in one acarine group (Listrophoridae) and artificial parthenogenesis is possible in ticks (Metastigmata). Gynogenesis is present in several species of haplo-diploid Mesostigmata (some Dermanyssidae, Phytoseiidae), although it is usually considered in connection with thelytoky. Current studies of the effects of ploidy level on morphological variation indicate greater character variability in diploid females than in haploid males. In some species of ticks thelytoky is expressed differentially even on an intraspecific level. One geographic strain of a species may have the ability to reproduce thelytokously, but if mated produces males and females.