Effects of adult age and body size on egg maturation in the parasitoid Gronotoma micromorpha (Hymenoptera: Figitidae)

Yajiao Wu,Yoshihisa Abe

doi:10.14411/eje.2021.038

Abstract

The cynipoid wasp Gronotoma micromorpha (Perkins) (Hymenoptera: Figitidae) is a parasitoid of the leaf miner Liriomyza trifolii (Burgess) (Diptera: Agromyzidae). The effects of adult age and body size on egg maturation in G. micromorpha were determined. The results showed that its egg load (number of mature eggs per female) increased when offered honey, water, but not hosts for 3 or 6 days after adult emergence. However, there was no significant difference in the egg loads of 3- and 6-day-old wasps. These findings and the results of previous studies on other cynipoid parasitoids suggest that when hosts are not available, females of parasitoid Cynipoidea enhance their reproductive capacity in anticipation of a future improvement in the availability of hosts by using carbohydrates and reserves stored during the larval stage. Moreover, large female wasps had higher egg loads throughout their lifetime. Given that rapid increases in the population density of L. trifolii are commonly reported in greenhouses, the demographic data of 0- and 3-day-old G. micromorpha females fed honey, need to be compared in the future. The effects of body size on the fecundity and longevity of G. micromorpha wasps should also be determined.

Highlights

Egg maturation in parasitoid wasps has been extensively investigated in order to clarify the life-history and reproductive strategies employed by these wasps (e.g., Rosenheim et al, 2000; Jervis et al, 2001, 2008)
From the viewpoint of reproduction, parasitoid wasps are classified as pro-ovigenic species, in which most or all of the potential lifetime egg complement is mature upon emergence, or synovigenic species, in which egg maturation continues throughout the adult stage (Flanders, 1950)
The egg load of G. micromorpha adults increased with age after emergence up to the midpoint of their adult life and thereafter remained constant when deprived of hosts; a similar relationship is reported for other cynipoid parasitoids, such as Ibalia leucospoides (Hochenwarth) (Hymenoptera: Ibaliidae) (Fischbein et al, 2013) and Leptopilina japonica Novković et Kimura (Hymenoptera: Figitidae) (Wang et al, 2018), but egg load continues to increase throughout adult life in Ganaspis brasiliensis Ihering (Hymenoptera: Figitidae) (Wang et al, 2018)

Summary

Introduction

Egg maturation in parasitoid wasps has been extensively investigated in order to clarify the life-history and reproductive strategies employed by these wasps (e.g., Rosenheim et al, 2000; Jervis et al, 2001, 2008). An ovigeny index, calculated by dividing the number of mature eggs upon emergence by potential lifetime fecundity, is widely used to assess a variety of reproductive traits of parasitoids (Jervis et al, 2001, 2008; Jervis & Ferns, 2004). In Cynipoidea, female parasitoids are generally pro-ovigenic or prosynovigenic (Kopelman & Chabora, 1986, 1992; Vårdal et al, 2003; Jervis et al, 2008; Fischbein et al, 2013; Wang et al, 2018; Wu & Abe, 2020). They do not feed on hosts (Bartlett, 1964; Abe, 2009) and their eggs are probably hydropic, i. Given that the prosynovigenic condition is intermediate between the pro-ovigenic and synovigenic, the likelihood of egg resorption should be determined in prosynovigenic cynipoid wasps deprived of hosts

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Conclusion