COPULATION, EGG PRODUCTION AND SEX‐RATIO IN PHYTOSEIULUS PERSIMILIS AND AMBLYSEIUS BIBENS (ACARI: PHYTOSEIIDAE)

Abstract

In Phytoseiulus persimilis Athias‐Henriot and Amblyseius bibens Blommers a relation was found between the duration of copulation and the resultant egg production. After 15 min of copulation no eggs were produced but after respectively 30, 60 and 90 min an increasing number of eggs were deposited. In P. persimilis the total number of eggs can be produced after one copulation of long duration but in A. bibens several copulations are necessary for total egg production. Evidence was found that egg deposition depends on the quantity of sperm transferred during insemination. Relatively more males developed from eggs deposited during the first day of egg deposition but males are produced throughout the whole egg‐laying period. Females of P. persimilis remain fertile throughout their life until they have deposited their total possible number of eggs. Three to 4 egg‐laying periods could be induced by copulations of 30 min duration. At each period relatively more males developed from eggs laid during the first days. Males of P. persimilis were found to be very fertile. The results obtained are discussed in relation to the reproductive strategy of both species. ZUSAMMENFASSUNG KOPULATION, EIZAHL UND GESCHLECHTSVERHÄLTNIS BEI PHYTOSEIULUS PERSIMILIS UND AMBLYSEIUS BIBENS (ACARI·PHYTOSEIIDAE) Bei Phytoseiulus persimilis Athias‐Henriot und Amblyseius bibens Blommers wurde ein Zusammenhang gefunden zwischen Kopulationsdauer und der resultierenden Eiproduktion Nach 15 Minuten Kopulation wurden keine Eier produziert; nach 30, 60 und 90 Minuten Kopulation hingegen wurde eine steigende Zahl Eier abgelegt. Bei P persimilis kann die totale Eizahl nach einer einzigen Kopulation von langer Dauer produziert werden, während bei A. bibens mehrere Kopulationen notwendig sind. Es wurden Anhaltspunkte gefunden, dass die Eizahl von der während der Besamung übertragenen Spermienmenge abhängt. Aus während der ersten Tage der Eiproduktion abgelegten Eiern entwickelten sich relativ mehr Männchen, doch wurden Männchen während der ganzen Eiablageperiode produziert. Weibchen von P. persimilis bleiben während ihres ganzen Lebens, bis sie alle Eier abgelegt haben, fertil. Drei bis vier Eiablageperioden konnten durch Kopulationen von 30 Minuten Dauer induziert werden. Bei jeder Periode entwickelten sich aus den in den ersten Tagen abgelegten Eiern relativ mehr Männchen. Männchen von P. persimilis erwiesen sich als sehr fertil. Die Resultate werden im Zusammenhang mit der Vermehrungsstrategie beider Arten diskutiert.

Sperm Reception and Egg Production of Mating-Interrupted, Single-Mated, and Multiple-Mated Females of Neoseiulus californicus (McGregor) at Different Temperatures (Acari: Phytoseiidae)

“…A positive correlation between the mating duration and female oviposition has been reported in many phytoseiid species, such as Amblyseius andersoni (Chant) (Amano and Chant, 1978b), N. bibens (Blommers) (Schulten et al, 1978), Phytoseiulus persimilis (Athias-Henriot) (Amano and Chant, 1978b;Schulten et al, 1978), A. potentillae (Garman), Typhlodromus pyri (Scheuten) (Overmeer et al, 1982), N. barkeri (Hughes) (Momen, 1993), N. womersleyi (Schicha) (Tsunoda andAmano, 2001), andA. deleoni Muma andDenmark (Zaher et al, 2007).…”

“…The size of the spermatophore (or the mass of sperm and seminal fl uid) injected by each male was estimated by measuring the size of the infl ated vesicle of the female spermatheca using a micrometer attached to a phase-contrast microscope. A positive relationship has been demonstrated between spermatophore size and resultant total egg production (Amano and Chant, 1978b;Schulten et al, 1978).…”

“…deleoni Muma andDenmark (Zaher et al, 2007). One mating is suffi cient to maximize the total egg production of females in a few species, including P. persimilis (Amano and Chant, 1978a;Laing, 1968;Schulten et al, 1978;Takafuji and Chant, 1976) and A. colimensis Aponte and McMurtry (Aponte and McMurtry, 1992). However, many species may increase egg production via multiple insemination; these include A. andersoni (Amano and Chant, 1978a), T. pyri (Overmeer et al, 1982), N. barkeri (Momen, 1993), N. womersleyi (Tsunoda and Amano, 2001), Kampimodromus aberrans (Oudemans) (Papas et al, 2007), and N. californicus (Gotoh and Tsuchiya, 2008).…”

Presumed Paternal Genome Loss During Embryogenesis of Predatory Phytoseiid Mites

“…Heterochromatinization in the part of the chromosomes was observed in eggs just after deposition (Nelson-Rees et al, 1980). Although cytological evidence is insufficient, this has been presented as pseudo-arrhenotoky: male-destined oocytes need to be fertilized to begin embryogenesis, and the heterochromatinization of the paternal genomes occurs in maledestined eggs, inducing the elimination of paternal genomes during embryogenesis, resulting in functionally haploid males (Schulten, 1985). This system was also described as "parahaploidy" in previous studies (e.g., Hoy, 1979) and was recently investigated as a form of "paternal genome loss" presented in several insects (Burt & Trivers, 2006).…”

“…However, Amano and Chant (1978) and Schulten et al (1978) showed that the amount of egg production is correlated with the amount of sperm accepted by females during copulation in Phytoseiulus persimilis, Amblyseius andersoni, and Amblyseius (= Neoseiulus) bibens. For instance, in a study of P. persimilis, in which copulation was artificially interrupted (Amano & Chant, 1978), the average number of eggs deposited gradually increased from 2.7 to 66.3 when the duration of copulation increased from 30 min to 130 min.…”