Cytological Evidence of Pseudo-arrhenotoky in Two Phytoseiid Mites, Phytoseiulus persimilis Athias-Henriot and Amblyseius womersleyi Schicha.

Presumed Paternal Genome Loss During Embryogenesis of Predatory Phytoseiid Mites

“…However, phenotypic sex is consistent with genetic sex (karyotype) in eggs produced with an even sex ratio under minimal prey conditions ( Fig. 5; see also Toyoshima & Amano, 1999). Actually, the number of male eggs is similar among different prey conditions, although the total number of eggs decreased gradually in relation to the number of prey items available to gravid females (Toyoshima & Amano, 1998).…”

“…By karyotyping just deposited eggs, the first and the following (presumed) male eggs were haploid in P. persimilis and in Amblyseius (=Neoseiulus) womersleyi determined from a previous study (Toyoshima & Amano, 1999). The time needed for the elimination of chromosomes differed from that of M. occidentalis, as reported by Nelson-Rees et al (1980).…”

“…Therefore, male diploidy in the early embryonic stages must be confirmed by extracting the first egg (male egg) from the female body cavity. In the first egg extracted from females of P. persimilis, diploid cells were observed in an early stage of embryogenesis (the exact stage was not confirmed), and the coexistence of haploid and diploid cells in the same egg was also seen at a later stage of embryogenesis (Toyoshima & Amano, 1999). Finally, only haploid cells were observed in eggs just before deposition.…”

Expression and function analyses of sex-lethal gene in Phytoseiulus persimilis

“…Overall, eggs develop into females were bigger and rounder than those develop into males in Phytoseiidae (Toyoshima & Amano 2012; Zhang 2017), but egg size is affected by many factors as well as its sex. So, it is not accurate to separate offspring of different sexes based on egg sizes (Toyoshima & Amano 1998). In some insects such as B. mori , sex of eggs can be determined through sex-limited strains that have an autosomal fragment having a dominant gene for egg color and larval marking, like (black larval marking) silkworm strain TWPB (Sakai et al 2014; Tanaka et al 2000).…”

“…Generally, it isn't easy to identify phytoseiid sexes before adult emergence. However, in almost all cases, the first egg of P. persimilis develops into a male, and the second egg develops into a female (Amano & Chant 1978; Toyoshima & Amano 1998; Lv et al 2019). Therefore, we collected and reared large amounts of the first two eggs, and were able to measure expression of this gene in immatures of both sexes.…”