Gradual, temperature-induced change of secondary sexual characteristics inTrichogramma pretiosuminfected with parthenogenesis-inducingWolbachia

Abstract

Intersex is an intermediate stage of sexual differentiation in insects. Determining intersex morphology and the cause of its production will aid in the understanding of the mechanism of sexual differentiation in insects. In this paper, Wolbachia-infected Trichogramma pretiosum (T. preW+) that shows thelytokous parthenogenesis were used as subjects. In order to determine the causes of the T. preW+ intersex and the influence of parental generation temperature on gradual changes in secondary masculinization in intersex offspring, we examined the occurrence of intersex offspring (F1 and F2 generation) after the parental generations were treated with high temperature (27, 29, 31, and 33 °C) and described the external morphology of the intersexes. The results showed that the T. preW+ parental generation temperature is positively correlated with the probability of intersex offspring. The probability of F1 intersex is significantly higher than that of F2 intersex in different high temperature. The degree of secondary masculinization in T. preW+ intersexes increases as parental generation temperature increases. In addition, our study first identified 11 intersex types in T. preW+ and found that the primary and secondary sexual characteristics showed a regular distribution. We also found that the D type and H type of intersex have the highest frequency of appearance. The external genitalia of most intersexes were female, and only three intersex types have male external genitalia. Conclusions were ultimately obtained: Wolbachia is a direct factor that causes the occurrence of intersexes, while high temperature is an indirect factor that determines the external morphology of intersexes. The effects of high temperature on T. preW+ intersexes is passed through the parental generation to offspring, and this maternal effect weakens as the number of generations increases. In T. preW+ intersex individuals, most exhibit female primary sexual characteristics, and secondary sexual characteristics exhibit signs of masculinization.

Effects of Sublethal Concentrations of Tetracycline Hydrochloride on the Biological Characteristics and Wolbachia Titer in Parthenogenesis Trichogramma pretiosum

“…Heterozygous diploid eggs develop into females, and homozygous diploid eggs develop into males, but the males are inviable or sterile [ 6 ]. Ning et al [ 25 ] speculated that the sex determination mechanisms of Trichogramma wasps might conform to genome imprinting. In this model, haploid eggs only contain a maternally imprinted sex-determination gene, and then they develop into males.…”

“…The sex ratio (SR) of offspring was also recorded for all the emerged adults. Based on the adults’ antennae characteristics [ 6 , 25 ], SR was calculated using the formulas: SR (% female) = [number of females/(number of females + number of males + number of intersex)] × 100; SR (% male) = [number of males/(number of females + number of males + number of intersex)] × 100; SR (% intersex) = [number of intersex/(number of females + number of males + number of intersex)] × 100.…”

“…Moreover, Wolbachia -infected Trichogramma brassicae would parasitize fewer host eggs compared with its bisexual strain [ 24 ]. Ning et al [ 25 ] found that Wolbachia was a direct factor that caused the occurrence of intersexes in T. pretiosum . However, it was unclear whether Wolbachia was completely eliminated because the Wolbachia titer was not tested in either female or male offspring in the above studies.…”

Effects of Wolbachia Infection, Parasitic Order, And Time Interval On The Outcome of Inter-Strain Intrinsic Competition Between Bisexual Strain And Wolbachia-Induced Thelytokous Strain of Egg Parasitoid, Trichogramma Dendrolimi

“…The single-parasitized and superparasitized host was recognized by the presence of one and two Trichogramma offspring, respectively, in a host egg. To collect the images of the immature stages of Trichogramma offspring with unchanged body size, the samples of Trichogramma offspring were treated with Carnoy's reagent for 2 h. The samples were dehydrated in a gradient of ethanol and glycerol solution according to the procedures described in our previous study (Ning et al 2019). Then, three samples at each stage were photographed using a camera with a macro lens (SMZ25; Nikon, Japan).…”

Μελέτη Κοινοτήτων Συμβιωτικών Βακτηρίων Σε Έντομα Αγροτικής Και Περιβαλλοντικής Σημασίας

“…Η συσχέτιση του αναπαραγωγικού φαινοτύπου με βακτήριο επιτεύχθηκε μετά από χορήγηση μείγματος αντιβιοτικών σε παρθενογενετικά θηλυκά του γένους Trichogramma, που είχε σαν αποτέλεσμα την εξάλειψη της αναπαραγωγικής ανωμαλίας και την επανεμφάνιση αρσενικών ατόμων. Επαναφορά της αρρενοτοκίας ή άτομα με ενδιάμεσα φυλετικά χαρακτηριστικά (intersex) παρατηρήθηκαν επίσης σε είδη του γένους Trichogramma και με την αύξηση της θερμοκρασίας (>30°C) (Ning et al, 2019;Stouthamer et al, 1990). Υπολογίζεται ότι το 15-31% των περιστατικών παρθενογένεσης στα υμενόπτερα προκαλείται από ενδοσυμβιωτικά βακτήρια (Ma and Schwander, 2017).…”