Egg load of lab-cultured Anaphes iole and effects of mate presence and exposure time on load depletion

Abstract

Anaphes iole Girault (Hymenoptera: Mymaridae) is a solitary egg parasitoid of Lygus bugs (Heteroptera: Miridae) in North America. This research considered factors that might impact the egg load of lab-cultured A. iole females, reared from Lygus hesperus Knight egg patches. The following hypotheses were tested: (1) egg load was related to body size and not affected by female age, and (2) egg load depletion was not affected by mate presence and time (in days) that females were exposed to host patches. Initial egg load averaged 48 mature eggs and no immature eggs were detected in the ovarioles of dissected females. Egg load was neither related to body size (hind tibia or forewing length) nor affected significantly by age (0, 1 or 2 days old honey-fed females). Mate presence (females with or without males) and exposure time (1, 3 or 5 days on the same host patch) had no effect on egg load depletion. Females usually depleted most of their egg load within 24 h. From 86 to 92% of females contained less than six mature eggs and no immature eggs after 1, 3 or 5 days of exposure to host patches. The results of this study suggest that A. iole females are certainly pro-ovigenic and initial egg load does not correlate with body size or age. Since mated and unmated females deplete most of their egg load in 24 h, time-efficient production of progeny may result when ovipositing parasitoids are exposed to suitable hosts for just a few days.

Egg Load and Body Size of Lab-cultured Cotesia marginiventris

“…Mohaghegh et al (1999) found no relationship between fecundity and body length of females of a Brazilian strain of Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae), which had been lab-cultured for at least five generations. Riddick (2005) found that egg load was not related to body size of Anaphes iole Girault (Hymenoptera: Mymaridae), which had been lab-cultured for more than six consecutive years. Contrary to these studies, body size can be used to predict the egg load or potential fecundity of lab-cultured C. marginiventris females.…”

“…The hind tibia was used to estimate body size. This character has been used previously for estimating body size of other parasitoids (Olson and Andow, 1998;Mills and Kuhlmann, 2000;Riddick, 2005). A digital imaging software program, Image-Pro Plus (1999), was used to make length measurements (in mm), with the aid of the dissecting microscope and camera system.…”

“…This relationship may not always hold true for very small-sized, short-lived parasitoids (Ellers and Jervis, 2004), lab-cultured parasitoids (Riddick, 2005) or lab-cultured predators (Mohaghegh et al, 1999).…”

Are Lab-cultured Anaphes iole Females Strictly Proovigenic?

“…A digital imaging software program, Image-Pro Plus (1999) and an inverted system microscope (Olympus, model #IX70) was used for counting all ovarian eggs at a magnification of 100-400X. Estimates of body size of females were not taken in this experiment, since a recent study (Riddick, 2005) indicated that neither hind tibia nor forewing length affected the initial egg load of A. iole females. A total of 24 females were dissected in this experiment.…”

“…Knowledge of the egg load (i.e., quantity of mature eggs contained within the ovaries) of newly emerged A. iole might be useful for estimating production potential of this parasitoid. Riddick (2005) indicated that the egg load of newly emerged A. iole was approximately 48 mature eggs before exposure to hosts and that 86-92% of females contained less than 6 mature eggs and no immature eggs after 1, 3 or 5 days of exposure to hosts. Also, egg load was not related to body size or affected significantly by age of A. iole females.…”