The effect of host size on quality attributes of the egg parasitoid, Trichogramma pretiosum

Abstract

In a study of the quality of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammidae), we compared female wasps emerging from natural hosts, parasitized in the laboratory or the field with those emerging from factitious hosts used for commercial mass production. Females from the natural hosts were larger, more fecund, and longer lived than those from the factitious hosts. Compared to small females, large female wasps are substantially more fecund when honey (carbohydrate) is available but marginally more fecund when honey is unavailable. The size of a female T. pretiosum depends on two factors: the size of the host egg from which it emerges even when the wasp was gregarious, and the number of conspecifics that emerge with it. The similarities in the size distribution of female wasps emerging from natural hosts, in conjunction with the mechanism by which Trichogramma measure host size and allocate eggs accordingly, suggests the hypothesis that size related components of fitness in female T. pretiosum are under strong selection in the field.

Phenotypic plasticity and fitness in egg parasitoids

“…However, most other proxies are infl uenced by the size of an individual and in most cases a positive relationship is found (West et al 1996, Nicol & Mackauer 1999 (but see the section on phenotypic variability). In several species of Trichogramma, size was found to be positively correlated with the number of oocytes at emergence, progeny produced over 24h, searching activity, host and female encounter rates for females and males respectively (Boldt 1974, Bai et al 1992, Kazmer & Luck 1995, Boivin & Lagacé 1999.…”

“…However, most other proxies are infl uenced by the size of an individual and in most cases a positive relationship is found (West et al 1996, Nicol & Mackauer 1999 (but see the section on phenotypic variability). In several species of Trichogramma, size was found to be positively correlated with the number of oocytes at emergence, progeny produced over 24h, searching activity, host and female encounter rates for females and males respectively (Boldt 1974, Bai et al 1992, Kazmer & Luck 1995, Boivin & Lagacé 1999.Longevity is critical for egg parasitoids especially when it comes to fi nding host patches. Most egg parasitoids are poor disperser and meteorological conditions such as wind, rain or solar radiation infl uence the capacity of these organisms to disperse to fi nd hosts (Fournier & Boivin 2000, Fatouros et al 2008.…”

Tabela de vida de fertilidade de três espécies neotropicais de Trichogrammatidae em ovos de hospedeiros alternativos como critério de seleção hospedeira

“…Características como volume do ovo hospedeiro, espessura do córion, conteúdo nutricional, idade e forma de postura dos hospedeiros podem afetar a qualidade dos parasitóides, bem como a porcentagem de parasitismo, razão sexual e o número de parasitóides/ ovo do hospedeiro (Hoffmann et al 2001;Roriz et al 2006;Rukmowati-Brotodjojo & Walter 2006). Desta forma, o desempenho do parasitóide está relacionado à qualidade do hospedeiro (Bai et al 1992;Schmidt 1994), sendo a escolha do hospedeiro de criação de suma importância na etapa de criação em laboratório, pois a escolha inadequada poderá comprometer o programa de controle biológico.…”

Biological parameters and parasitism capacity of Telenomus remus Nixon (Hymenoptera: Platygastridae) reared on natural and factitious hosts for successive generations

“…Oviposition peak of different species of egg parasitoids from the genus Trichogramma, for example, have been already reported in the literature on the first day after adult emergence (Bai et al, 1992;Volkoff and Daumal, 1994). This is usually a consequence of most of these parasitoids to have the capacity to store a full complement of mature eggs in the ovaries or oviducts and complete oogenesis either before or shortly after adult emergence (pro-ovigenic parasitoids) (Mills and Kuhlmann, 2000) and, thus, adults emerge ready to lay eggs.…”