Genetic evidence for biparental males in haplo-diploid predator mites (Acarina: Phytoseiidae)

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

“…Amano and Chant(1978b)and Schulten et al(1978) showed that adult females of phytoseiid mites increased egg production relative to the duration of copulation.The results suggested that the production of eggs required a signal of insemination.In addition,it was shown that the effect of x-ray irradiation on adult males was transmitted to the offspring of both sexes in Amblyseius bibens,Phytoseiulus persimilis (Helle et al,1978)and Metaseiulus occidentalis (Hoy,1979 had deposited first eggs,were mounted at15,30,45and60minutes,respectively,after oviposition to identify the timing for the shell of the second egg to form.Timing for dissecting the idiosoma and extracting eggs from the body cavities of female P.persimilis was then determined from these observations.After the eggs had been extracted from the female body cavities,the chromosomes of the eggs were observed in the manner described above.…”

Presumed Paternal Genome Loss During Embryogenesis of Predatory Phytoseiid Mites

“…After expansion of other eggs, the first egg moves into the uterus in the ventral region and forms an eggshell there. It was also shown at the almost same time that X-ray irradiation on adult males (fathers) induced sterility in male offspring (sons) in P. persimilis, A. bibens (Helle et al, 1978), and Metaseiulus (= Galendromus) occidentalis (Hoy, 1979). No daughters emerged, and total developing offspring was low in these experiments.…”

Evolution of pseudo-arrhenotoky

“…This is strong evidence that sex ratio shifts do not occur as a result of a simple son-first pattern in combination with an effect of predator cues on brood size, but that it is the result of genuine sex-ratio control. It should also be noted that this evidence was obtained for phytoseiid species whose pseudo-arrhenotokous state is well documented by cytological and or genetical evidence (Helle et al, 1978;Hoy, 1979;Nelson-Rees et al, 1980).…”

“…These experiments strongly suggest that phytoseiid mites are capable of sex-ratio control. Even more interestingly, the experiments were done precisely with the phytoseiid species where the diploid origin of the males and paternal genome loss are proven facts: P. persimilis and T. occidentalis (Helle et al, 1978;Hoy, 1979;Nelson-Rees et al, 1980;Schulten, 1985). Why then are the sex ratios of most phytoseiid species so heavily skewed towards females?…”