Effect of adult feeding and timing of host exposure on the fertility and longevity of the parasitoid Anaphes flavipes

Abstract

The parasitoid Anaphes flavipes (Foerster) (Hymenoptera: Mymaridae) is a gregarious egg parasitoid which is widely used in biological control against important crop pest beetles of the genus Oulema (Coleoptera: Chrysomelidae). Here, we present the first experimental examination of the influence of adult feeding and timing of host exposure on the longevity and fertility of this parasitoid. We confirmed a positive effect of adult feeding on longevity of both sexes. Fed parasitoids lived 3× longer than unfed ones. On the other hand, adult feeding and feeding time had no effect on female fertility. The number of hatched offspring was not increased by adult feeding, which suggests that the parasitoid emerges with already mature ovaries (proovigenic type). However, the fertility of fed females was strongly influenced by the timing of host egg exposure. By providing distinct groups of parasitoids with host eggs at different times, we were able to show lower fertility of fed females that had been offered host eggs more than 24 h after hatching. Our results thus show that the parasitoid's fertility is determined by her age at the time of parasitization rather than by feeding.

Female manipulation of offspring sex ratio in the gregarious parasitoidAnaphes flavipesfrom a new two-generation approach

“…Anaphes flavipes were reared from host eggs ( Oulema spp.) collected in cereal fields (barley and wheat) in two localities in Prague-Suchdol, Czech Republic (GPS: 50.1385N, 14.3695E; 50.1367N, 14.3638E) from the end of April until the end of June in the years 2012, 2015, 2016 identically as in our previous studies (Samková et al 2019a, b, c, 2020, recorded in Suppl. materials).…”

“…Mated females (not older than 24 hours post emergence) were placed in Petri dishes with host eggs. Before the start of the experiment and during the experiment, the females were not fed, and they had free access to water (modified from Samková et al 2019a, b, c, 2020).…”

“…The Oulema species complex, including two ecologically very close species of O. duftschmidi Redtenbacher, 1874 and O. melanopus Linnaeus, 1758, was used identically as in our previous studies (Samková et al 2019a b c, 2020) and in other studies (Anderson & Paschke 1968, 1969), because these species occur together in the same localities at the same time (Van de Vijver et al 2019, Samková et al 2020) and are distinguished only on the basis of genital preparation (Bezděk & Baselga 2015). We consider these species particularly safe and convenient for our experiments because 1) their host eggs do not differ in length and weight (Samková et al 2019a), 2) the wasps A. flavipes are not host-specific (Samková et al 2020) and 3) the offspring of these two host species do not differ in size (Samková et al 2019a) and 4) show no morphological abnormalities (unpublish.).…”

“…Host eggs were removed along with a 1 cm long piece of leaf and then used in the experiments. Since A. flavipes females refuse host eggs older than 72 hours (Anderson & Paschke 1968), we used eggs not older than 24 hours (modified from Samková et al 2019a, b, c, 2020).…”

Scarcity of hosts for gregarious parasitoids indicates an increase of individual offspring fertility by reducing their own fertility

“…Mated females (not older than 24 hours post-emergence) were placed in Petri dishes with host eggs. Before the start of the experiments and during the experiment, all females were not fed, but they had free access to water (taken from Samkova et al 8,15,69,70 ).…”