Effects of age and repeated mating on male sperm supply and paternity in a parasitoid wasp

Abstract

International audiencePost-copulatory paternity biases after female multiple mating are major constraints on both male and female reproductive systems. The outcome of paternity in certain situations is only controlled directly by male sperm stock. This was tested experimentally in the parasitoid wasp Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), in which sperm stocks are small (several hundred) and the fertilizing efficiency of stored sperm is high (the ratio of sperm stored/fertilized eggs is about 0.75). Sperm in seminal vesicles and paternity of males of different status (virgin young, virgin old, or young previously mated) were measured after female single and double mating. The amount of sperm in the seminal vesicle differed according to male status (increasing from previously mated males to old males), but there was no difference in sperm stored by females after a single mating. In double mating experiments with two males of different status, paternity increased linearly with the relative amount of sperm in seminal vesicles. Paternity distribution conforms to ‘a fair raffle' of sperm from both donors following complete mixing of sperm prior to fertilization. Thus, in a female multiple mating context, male fitness depends principally on their sperm stock, which in turn depends on life history parameters, such as age and previous mating

Influence of body size on fecundity and sperm management in the parasitoid wasp Anisopteromalus calandrae

“…). These results show that females may mate more than once to acquire a sufficient number of sperm, although they do not actually accept more than one mating (see above) even if they are sperm‐depleted (Do Thi Khanh et al ., ; Bressac et al ., ). One possible explanation for this is that, although females could utilize abundant hosts in our experiment, such a circumstance may be very rare in nature and they are unlikely to achieve the full potential of their fecundity.…”

“…During oviposition, in which sperm is released from the spermatheca to fertilize eggs, some sperm may again be lost. Although the efficiency of fertilization is generally low in insects and internally fertilizing animals, A. calandrae along with some parasitoid wasps has a very high fertilization efficiency (Do Thi Khanh et al ., ; Bressac et al ., ), as also confirmed in present study (Figs b and ).…”

“…The adults appear to mate within their natal patches, and their sex ratios follow the predictions of local mate competition theory (Hamilton, ): the proportion of female offspring increases with a decrease in the number of females laying eggs in a patch (Nishimura & Jahn, ). Sperm stocks in the female spermatheca are relatively low (fewer than several hundred sperm), and females efficiently use the sperm to produce female offspring (the efficiency of stored sperm in the spermatheca that are used for fertilization is close to one) (Do Thi Khanh et al ., ; Bressac et al ., ).…”

Beyond sex allocation: the role of mating systems in sexual selection in parasitoid wasps

“…In parasitoids, first-male sperm precedence has been established in Trichogramma euproctidis (Damiens & Boivin, 2005; Martel et al , b 2008), Habrobracon hebetor (Ode et al , 1995) and Nasonia vitripennis (Holmes, 1974), while lack of sperm precedence (i.e. random sperm usage) has been found in Anisopteromalus calandrae Howard (Pteromalidae), Bressac, Khanh & Chevrier, 2009) and Diachasmimorpha longicaudata Ashmead (Braconidae), Martínez-Martínez et al , 1993). In the latter case, the timing of the second mating was found to be important, with the second male siring 75% of the progeny if there was a 24 h interval between matings (Martínez-Martínez et al , 1993).…”

Les hyménoptères parasitoïdes

“…Le nombre de gamètes dans les vésicules séminales augmente avec l'âge [17,18]. Après l'émergence, on en dénombre, stockés dans les vésicules séminales, environ 3 100 chez D. basalis [18], 4 000 chez A. calandrae [19], et plus de 20 000 chez N. vitripennis [20]. Leur viabilité dans les vésicules séminales n'est pas affectée par l'âge, elle est d'environ 56 % chez D. basalis à 1 j et 30 j [18].…”