Polyembryony in Copidosoma koehleri Blanchard

Doutt, Richard L.

doi:10.1086/281554

Cited by 67 publications

(37 citation statements)

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“…43), including the astute suggestion of Silvestri (38) that soldier larvae may arise from embryos lacking a ''germ cell determinant.'' Silvestri's explanation was criticized by several workers (44)(45)(46)(47), but our results support his idea by showing that (i) embryos with PGCs develop into reproductive larvae whereas embryos lacking PGCs develop into soldiers, and (ii) ablation of the B 4 blastomere usually results in production of only soldiers. C. floridanum eggs and blastomeres are very small, and it is possible in our ablation experiments that we sometimes failed to kill the target cell, damaged a neighboring cell, or damaged the egg itself during injection into a host.…”

Section: Discussionsupporting

confidence: 76%

Caste determination in a polyembryonic wasp involves inheritance of germ cells

Donnell

Corley

Chen

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Social insects are characterized by the development of castes in which some colony members reproduce whereas others function as altruistic helpers. The conditional switch controlling caste formation usually involves environmental stimuli that act on processes that regulate development of individuals. Unlike other social species, embryos of polyembryonic wasps develop clonally to produce large numbers of genetically identical offspring and two morphologically distinct castes. All embryos in a clone exist in an identical environment, the host, yet develop into either reproductive larvae that mature into adult wasps or soldier larvae whose function is defense. Here, we report that caste determination in Copidosoma floridanum involves inheritance of germ cells. Expression of a C. floridanum homolog (Cf-vas) of the germ cell marker Vasa indicated that the B4 blastomere in four cell-stage embryos is specified as a primordial germ cell. Vas expression later in development further indicated that embryos developing into reproductive larvae possess primordial germ cells whereas embryos developing into soldier larvae do not. Ablation of the B4 blastomere resulted in most broods containing only soldiers whereas ablation of other blastomeres produced broods containing both castes. These results indicate that soldier larvae are obligately sterile and reveal a previously unknown role for germ cells in caste formation.parasitoid ͉ polyphenism ͉ social evolution ͉ polyembryony G enetic relatedness has long been considered a key factor in the transition from individuality to sociality (1-4). Most social species are insects like ants, bees, and termites that form colonies of close relatives comprised of reproductive and altruistic (nonreproducing) helper castes. Castes have also evolved in selected groups of aphids, thrips, and polyembryonic wasps (5-10). The conditional switch controlling caste formation is usually an environmental stimulus (i.e., diet, temperature, density, pheromones) that acts on internal processes regulating development (11)(12)(13)(14). Genetic factors have also been implicated in how individuals respond to environmental stimuli (15-18). The collective effect of these inputs is that reproductive caste members have well developed gonads whereas altruistic helpers (workers and soldiers) are functionally sterile or are capable of only limited reproduction (7,14). Despite the pronounced differences in behavior and morphology of different castes, the developmental processes regulating caste formation are largely unknown (11)(12)(13)(14)(15)(16)(17)(18)(19)(20).Unlike other social insects, polyembryonic wasps in the family Encyrtidae are parasites whose eggs develop clonally (21,22). Copidosoma floridanum oviposits into the eggs of the moth Trichoplusia ni. The C. floridanum egg initially forms a single morula stage embryo comprised of Ϸ200 embryonic cells surrounded by a polar body-derived extraembryonic membrane. After hatching of the host egg, the primary morula gives rise to an increasing number of embryos, ca...

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Section: Discussionsupporting

confidence: 76%

Caste determination in a polyembryonic wasp involves inheritance of germ cells

Donnell

Corley

Chen

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…In Copidosoma floridanum and congeners, the sterile soldiers are predominantly or even exclusively females (Doutt 1947;Grbic et al 1992;Ode and Strand 1995;Keasar et al 2006;Giron et al, forthcoming; for Copidosoma sosares, P. J. Ode and M. R. Strand, personal communication), suggesting that the primary function of soldiers (at least in mixed-sex full-sibling broods) is sex ratio manipulation (conflict) and not defense and facilitation.…”

Section: A General Model Of Soldier Production and Functionmentioning

confidence: 99%

“…Alternative possibilities have been suggested to explain sex-biased soldier production. Doutt (1947) suggested that the haploid genome of males could be responsible for sex differences in Copidosoma development. However, male soldiers do exist, so it is reasonable to assume that the proportions of embryos of each sex developing as sterile soldiers is unconstrained by ploidy.…”

Section: A General Model Of Soldier Production and Functionmentioning

confidence: 99%

Spiteful Soldiers and Sex Ratio Conflict in Polyembryonic Parasitoid Wasps

Gardner

Hardy²,

Taylor³

et al. 2007

The American Naturalist

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The existence of spiteful behaviors remains controversial. Spiteful behaviors are those that are harmful to both the actor and the recipient, and they represent one of the four fundamental types of social behavior (alongside selfishness, altruism, and mutual benefit). It has generally been assumed that the conditions required for spite to evolve are too restrictive, and so spite is unlikely to be important. This idea has been challenged in recent years, with the realization that localized competition can relax the conditions required for spite to evolve. Here we develop a theoretical model for a prime candidate for a spiteful behavior, the production of the sterile soldier caste in polyembryonic wasps. Our results show that (a) the biology of these soldiers is consistent with their main role being to mediate conflict over the sex ratio and not to defend against competitors and (b) greater conflict will occur in more outbred populations. We also show that the production of the sterile soldier caste can be classed as a spiteful behavior but that, to an extent, this is merely a semantic choice, and other interpretations such as altruism or indirect altruism are valid. However, the spite interpretation is useful in that it can lead to a more natural interpretation of relatedness and facilitate the classification of behaviors in a way that emphasizes biologically interesting differences that can be empirically tested.

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“…, 2004; Gordon & Strand, 2009). Development of other Copidosoma species proceeds similarly to C. floridanum although the number of progeny produced per host varies from less than a hundred to several thousand (Doutt, 1947; Cruz, 1981; Walter & Clarke, 1992; Carroll et al. , 2007).…”

Section: Introductionmentioning

confidence: 99%

Phenotypically plastic traits regulate caste formation and soldier function in polyembryonic wasps

Smith

Milton

Strand

2010

J of Evolutionary Biology

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Polyembryonic encyrtid wasps are parasitoids that have evolved a clonal form of embryogenesis and a caste system where some progeny become reproducing wasps whereas others develop into a sterile soldier caste. Theory based on the biology of Copidosoma floridanum predicts that the primary role of soldier larvae is to mediate conflict over sex ratio, which also favours female‐biased soldier production. Other data, however, suggest that female‐biased soldier production reflects a developmental constraint. Here, we assessed whether female‐biased soldier function by polyembryonic wasps reflects sex‐specific adaptation or constraint by conducting comparative studies with Copidosoma bakeri, a species that produces clutch sizes similar to C. floridanum yet rarely produces broods associated with sex ratio conflict. Our results indicate that the oviposition behaviour of adults, development of progeny and function of soldier larvae differ greatly between C. bakeri and C. floridanum. These findings indicate that caste formation and soldier function in polyembryonic encyrtid wasps are regulated by phenotypically plastic traits. Our results further suggest that the primary function of the soldier caste in some species is defence of host resources from competitors whereas in others it is the resolution of sex ratio conflict.

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Polyembryony in Copidosoma koehleri Blanchard

Cited by 67 publications

References 0 publications

Caste determination in a polyembryonic wasp involves inheritance of germ cells

Caste determination in a polyembryonic wasp involves inheritance of germ cells

Spiteful Soldiers and Sex Ratio Conflict in Polyembryonic Parasitoid Wasps

Phenotypically plastic traits regulate caste formation and soldier function in polyembryonic wasps

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