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Diversity of Ooencyrtus spp. (Hymenoptera: Encyrtidae) parasitizing the eggs of Stenozygum coloratum (Klug) (Hemiptera: Pentatomidae) with description of two new species.

ABSTRACT: Ooencyrtus spp. (Hymenoptera, Chalcidoidea, Encyrtidae) are important natural enemies of agricultural and forest insect pests, and are distributed worldwide. Their reduced dimensions, highly variable morphological characters and possible effect of wide host range and abiotic factors, make correct identification at the species level particularly difficult. This paper combined molecular, morphological, and biological data to characterize a group of Ooencyrtus spp. emerging from the eggs of the variegated caper bug, Stenozygum coloratum in the east Mediterranean area. COI and ITS2 sequencing revealed the presence of six and five divergent clades, respectively. Three clades were identified as Ooencyrtus telenomicida, Ooencyrtus pityocampae and O. pistaciae. Two clades represent new species which are here described and named Ooencyrtus zoeae and Ooencyrtus mevalbelus. These features were combined with reliable morphological characters to facilitate the separation of these species. A dichotomous key and a new synonymy are proposed. Ooencyrtus pistaciae had two distinct COI clades but only one ITS2 clade. Crossbreeding trials that included Ooencyrtus telenomicida, Ooencyrtus melvabelus sp. nov. and Ooencyrtus zoeae sp. nov. confirmed their reproductive isolation. COI sequences showed 0-0.8% and 4-9% within and between-species genetic differences, respectively. ITS2 showed 0.4-5.9% genetic differences between species, with no genetic differences within species. Haplotype diversity of Israeli and Turkish populations of the various species was 0-0.98 and was particularly low in Ooencyrtus pityocampae, whose Israeli population showed no diversity. The discovery of the Ooencyrtus spp. on the eggs of the caper bug, and their abundance support the idea that the bug can be used as an alternative host for augmentation of populations of these parasitoids in agricultural and forestry systems.

SUBMITTER: Samra S

PROVIDER: S-EPMC6221264 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Diversity of Ooencyrtus spp. (Hymenoptera: Encyrtidae) parasitizing the eggs of Stenozygum coloratum (Klug) (Hemiptera: Pentatomidae) with description of two new species.

Samra Shahar S Cascone Pasquale P Noyes John J Ghanim Murad M Protasov Alex A Guerrieri Emilio E Mendel Zvi Z

PloS one 20181107 11

Ooencyrtus spp. (Hymenoptera, Chalcidoidea, Encyrtidae) are important natural enemies of agricultural and forest insect pests, and are distributed worldwide. Their reduced dimensions, highly variable morphological characters and possible effect of wide host range and abiotic factors, make correct identification at the species level particularly difficult. This paper combined molecular, morphological, and biological data to characterize a group of Ooencyrtus spp. emerging from the eggs of the var ...[more]

PMID: 30403678

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Project description:BackgroundWolbachia bacteria are estimated to occur in more than half of all insect species. In Hymenoptera, Wolbachia often manipulates its host's reproduction to its own advantage. Wolbachia is likely the reason that males are rare in the uniparental Ooencyrtus mirus Triapitsyn & Power (Hymenoptera: Encyrtidae). The likelihood of producing male offspring can be increased by giving mothers a continuous supply of Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) host eggs to parasitize for 2-3 weeks, by feeding the parents antibiotics, or by rearing parent wasps at high temperatures; all variables that have been shown to correlate with depleting Wolbachia titers in other organisms. The purpose of the current study was to determine whether thelytoky in O. mirus is due to Wolbachia, and if so, at what time in development the sex change occurs. We also wished to determine if Wolbachia removal results in the production of intersexes, as in some other hymenopterans. Finally, mating behavior was observed to see if and where it breaks down as a result of the species becoming thelytokous.MethodsFemales were collected from parental lines of O. mirus reared at 26, 30, 31, 32, 33, 34, and 36 °C. The offspring of these females were reared at 26 °C, and their sex-ratio was determined. In a subsequent experiment, the parental generation was switched between 26 °C and 36 °C during development to narrow down the critical period at which changes occurred that subsequently affected the sex-ratio of their offspring.ResultsThe sex ratio was male biased in the offspring of O. mirus parents reared at 34 °C and 36 °C (high temperatures), even if the offspring themselves were reared at 26 °C. The constant temperature at which the percentage of males started to increase after two generations was 31 °C (10% males), rising to 39% males at 33 °C, and 100% males at 34 °C and 36 °C. Lasting more than 2 days, the critical period for the change toward a male biased sex ratio was during the second half of the parent's development. Molecular diagnostic assays confirmed that O. mirus females contain Wolbachia and males do not. Examination of preserved males and male-female pairs under a dissecting microscope showed no signs of intersex characters. Observation of the mating behavior of live O. mirus showed that males initiate courtship by drumming their antennae on a female's antennae, but after a few seconds, the females typically turn and walk away. However, a few instances of possible copulation were noted.ConclusionsAs hypothesized, the results indicated that thelytoky in O. mirus is likely mediated by Wolbachia bacteria. To maximize the population growth rate without generating males, the best temperature for mass rearing this species is 30 °C.

Dataset Information

Diversity of Ooencyrtus spp. (Hymenoptera: Encyrtidae) parasitizing the eggs of Stenozygum coloratum (Klug) (Hemiptera: Pentatomidae) with description of two new species.

Publications

Diversity of Ooencyrtus spp. (Hymenoptera: Encyrtidae) parasitizing the eggs of Stenozygum coloratum (Klug) (Hemiptera: Pentatomidae) with description of two new species.

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