Host stage selection of the mealybug parasitoid Anagyrus spec. nov near sinope

Abstract

The mealybug parasitoid Anagyrus spec. nov near sinope (Hymenoptera: Encyrtidae) is an undescribed parasitoid of the Madeira mealybug, Phenacoccus madeirensis Green (Homoptera: Pseudococcidae). We investigated the preference of Anagyrus spec. nov near sinope for six developmental stadia (first-and second-instar nymphs, third-instar immature females, third-or fourth-instar immature males, pre-reproductive adult females, and ovipositing adult females) of P. madeirensis and the fitness consequences of the host stage selection behavior. In the no-choice test, Anagyrus spec. nov near sinope parasitized and completed development in all host stadia except third-instar immature males. When all host stadia were offered simultaneously, the parasitoids preferred third-instar immature and pre-reproductive adult females. Dissection of the stung mealybugs revealed that the clutch size (number of eggs per host) was approximately four and three in the third-instar and pre-reproductive females, respectively, and one egg per first-instar nymph. Parasitoids emerged from P. madeirensis parasitized at third-instar or pre-reproductive adult female completed development in the shortest duration, achieved a higher progeny survival rate, larger brood and body size, and the lowest proportion of males. We showed that the continued development of mealybugs had significant influence on the fitness of the parasitoids. Although deposited as eggs in first-or second-instar nymphs, parasitoids emerged from mummies that had attained third-instar or adult development achieved similar progeny survival rate, brood size, body size, and sex ratio as those parasitoids deposited and developed in third-instar or adult mealybugs. By delaying larval development in young mealybugs, Anagyrus spec. nov near sinope achieved higher fitness by allowing the parasitized mealybugs to grow and accumulate body size and resources. We suggest that the fitness consequence of host stage selection of a koinobiont parasitoid should be evaluated on both the time of parasitism and the time of mummification.

Influence of Temperature and Mating Status on the Development and Fecundity of the Mealybug Parasitoid,Anagyrussp. nov. nr.sinopeNoyes and Menezes (Hymenoptera: Encyrtidae)

“…nov. nr. sinope (Chong & Oetting 2006a). The adult mealybugs did not continue to increase their body sizes through growth after parasitism; effectively providing the developing parasitoid larvae with a fixed amount of resources.…”

“…nov. nr. sinope, actively select hosts of a specific age or size that have sufficient resources to produce progeny of a higher fitness (Godfray 1994;Harvey et al 1998;Zaviezo & Mills 2000;Milonas 2005;Chong & Oetting 2006a). Adult and second instar P. madeirensis represent hosts of two different qualities for Anagyrus sp.…”

“…nov. nr. sinope preferred third instar immature and prereproductive adult female P. madeirensis for oviposition and progeny development (Chong & Oetting 2006a). The parasitoids that developed in these preferred host stages had a shorter developmental time, a lower mortality rate, a higher proportion of females, and larger brood and body sizes.…”

“…However, younger nymphs that had continued development to become older nymphs before mummification produced a similar progeny number and sex ratio as those mealybugs that were parasitized as adults. Chong & Oetting (2006a) (Chong & Oetting 2006b). Phenacoccus madeirensis reared on sprouted russet potatoes ( Solanum tuberosum L., Solanaceae) were provided as hosts in the laboratory colony.…”

“…All adult parasitoids were collected and preserved in 70% ethanol within 6 h of eclosion, and their left hind tibial length was measured with a micrometer under dissecting microscopes. Hind tibial length was used as a surrogate for the body length and the fitness of the parasitoid (Sagarra et al 2001;Chong & Oetting 2006a). Thirty seven and 46 replicates were prepared for the adult and second instars, respectively.…”