Cytoplasmic male killing elements in Adalia bipunctata (Linnaeus) (Coleoptera: Coccinellidae)

Abstract

A wild sample of Ada/ia bipunctata larvae and pupae were collected from Surrey, and F1 virgin adults mated. The sex ratio produced by these pairs was found be be variable, 22 pairs produced a sex ratio consistent with a 1:1 sex ratio, but four produced a strong female bias. Daughters and males from biased broods were mated to adults from non-biased broods of different parentage.Males and females from unrelated families were crossed. Where the female was taken from a biased clutch, the biased sex ratio trait recurred in a high proportion of cases. Where males from such broods were crossed, or females from broods with no history of bias were mated, sex ratios consistent with 1:1 were obtained. Pairs producing a strong female bias showed hatch rates which were approximately half that of crosses producing non-biased sex ratios. Treatment with tetracycline in golden syrup cured females who showed the biased sex ratio trait. Daughters conceived after this treatment produced normal sex ratios. Females fed purely on golden syrup, as a control, continued to produce female biased sex ratios until treated with tetracycline. We therefore suggest that an unknown bacterium, transmitted through egg cytoplasm but not sperm, is responsible for the early mortality of male embryos and thus a bias in the secondary sex ratio. The contribution that the study of the Coccinellidae can make to theories concerning the incidences and evolution of male killing elements is discussed in relation to egg cannibalism.

Male-killingWolbachiain a flour beetle

“…Incomplete transmission has been reported for Wolbachia (Ho¡man et al 1990) as well as other malekilling infections (Ebbert 1993). Male-lethal infections involving death during embryogenesis are often associated with egg hatch rates that are approximately half or lower than normal (Hurst et al 1992(Hurst et al , 1996Ebbert 1993). The reversion to a sex ratio of unity and increased egg hatch rates following antibiotic treatment not only provide strong support for male killing but also argue against meiotic drive as an alternative explanation for the sex-ratio distortion.…”

The effect of infection with male-killing Rickettsia on the demography of female Adalia bipunctata L. (two spot ladybird)

“…In southern England, seven per cent of female Adalia bipunctata (two spot ladybird) are host to a bacterium of the genus Rickettsia, which is transmitted to their offspring, and is lethal to male progeny (Hurst et at., 1992(Hurst et at., , 1993Werren et at., 1994). The evolutionary cause of the male-killing behaviour of inherited microorganisms has recently come under scrutiny (Skinner, 1985;Werren, 1987;Hurst, 1991;.…”

Male-killing bacterium in a fifth ladybird beetle, Coleomegilla maculata (Coleoptera: Coccinellidae)

“…The discovery of a male-killing bacterium in C. maculara brings the number of coccinellid genera (and species) known to harbour male-killers to five, and suggests that there may be many more genera and species that do so. The thesis that the presence of sibling egg cannibalism in members of this group has rendered them very prone to invasion by male-killing symbionts (Hurst et al, 1992;Hurst & Majerus, 1993) appears to be corroborated. In addition, the fact that C. maculata IS a species which has been well-worked in the laboratory over a period of more than 20 years suggests that many more species of coccinellid may be infected with male-killing bacteria than previously thought.…”

“…The susceptibility of the trait to antibiotics was tested as described by Hurst et al (1992). In short, the F1 females above showing the sex ratio trait (Table 2a) were allowed to feed daily for 1 h over a period of 14 days upon either tetracycline in golden syrup (10 per cent w/w), or golden syrup alone.…”

“…bipunctata (Hurst et al, 1992), Harinonia axyridis (Matsuka et al, 1975), Menochilius sexmaculatus (Niijima & Nakajima, 1981), and Hippodamia convergens (Shull, 1948). We here investigate the sex ratio produced by crosses of Coleomegilla maculata (DeGeer), a coccinellid which also exhibits sibling egg cannibalism, and in which the survival of neonate larvae is thought to be positively affected by an egg meal (Smith, 1961;Pienkowski, 1965).…”