Late male-killing phenomenon found in a Japanese population of the oriental tea tortrix, Homona magnanima (Lepidoptera: Tortricidae)

Abstract

A female-biased sex ratio was found in the oriental tea tortrix, Homona magnanima (Lepidoptera: Tortricidae), in Tsukuba, Ibaraki, Japan. There was no difference in mean egg hatch between the all-female and normal strains. Greater than 50% mortality was observed in the all-female strain larvae, suggesting that female-only broods are produced as a result of late male-killing. The female-biased sex ratio was maternally inherited and maintained, even when females were backcrossed with males of the normal strain, thus implicating cytoplasmic parasitism as its cause. The phenomenon was persistent in the presence of antibiotics, and was not due to infection by agents that cause other male-killing phenomena, such as Rickettsia, Wolbachia, Spiroplasma, or protozoan parasites. When a homogenate of dead male larvae of the all-female strain was inoculated in normal-strain larvae, this male-killing trait was transmitted to the next generation; thus, its causative agent is probably transmitted horizontally as well.

Novel RNA sequences associated with late male killing inHomona magnanima

“…(a) Purification of the male-killing agent Late male killing in H. magnanima is transmitted vertically only from mothers (Morimoto et al 2001). The causal agent of late male killing in H. magnanima is not Wolbachia, Spiroplasma, Rickettsia, Flavobacteria or the gamma proteobacteria, which were reported to be early male-killing agents, or the protozoa reported to be the late male-killing agent in mosquitoes.…”

“…The normal strain of H. magnanima was collected from Itsukaichi, Tokyo, Japan, in 1999. These strains were maintained as described previously (Morimoto et al 2001).…”

“…Late male killing has previously been recorded only in mosquitoes (Andreadis & Hall 1979;Andreadis 1985), caused by a microsporidian parasite, in Drosophila subquinaria ( Jaenike 2007), caused by Wolbachia, and in strains of the oriental tea tortrix, Homona magnanima (Morimoto et al 2001), at Ibaraki, Japan. The causal agent in H. magnanima is transmitted both vertically and horizontally.…”

Gross morphology and histopathology of male-killing strain larvae in the oriental tea tortrix Homona magnanima (Lepidoptera: Tortricidae)

“…Five clades of bacteria have been identified as early male-killing agents (Rickettsia, Wolbachia, Spiroplasma, Flavobacteria, and a gamma proteobacterium) (Hurst et al, 2003;Majerus, 2003). Late male killing was previously recorded only in mosquitoes and is caused by a microsporidium (Andreadis and Hall, 1979;Andreadis, 1985) but our group recently found late male killing in the oriental tea tortrix Homona magnanima (Diakonoff) collected from Ibaraki Prefecture, Japan (Morimoto et al, 2001). Morimoto et al (2001) reported that the causative agent of late male killing of H. magnanima is maternally heritable, horizontally transmissible, and microorganisms that cause other male-killing phenomena, such as Wolbachia, Spiloplasma, Rickettsia, or microsporidia, are not responsible.…”

“…LMK females were crossed with NSR males and maintained in the laboratory (Morimoto et al, 2001). In each generation, 20 female and 30 male pupae were placed in a plastic box (30ϫ20ϫ5 cm) with wax paper for oviposition.…”