Offspring Sex Ratios in Parasitoid Wasps

1987 ◽  
Vol 62 (4) ◽  
pp. 367-396 ◽  
Author(s):  
Bethia Hurlbutt King
Keyword(s):  
Sex Ratios ◽  
Parasitoid Wasps ◽  
Offspring Sex

A new male-killing parasitism:Spiroplasmabacteria infect the ladybird beetleAnisosticta novemdecimpunctata(Coleoptera: Coccinellidae)

Parasitology ◽  
2006 ◽  
Vol 132 (6) ◽  
pp. 757-765 ◽  
Author(s):  
M. C. TINSLEY ◽  
M. E. N. MAJERUS
Keyword(s):  
Phylogenetic Analysis ◽  
Sex Ratio ◽  
High Efficiency ◽  
Sex Ratios ◽  
Egg Hatch ◽  
Hatch Rate ◽  
Male Killing ◽  
Offspring Sex ◽  
Novel Host ◽  
Males And Females

Whilst most animals invest equally in males and females when they reproduce, a variety of vertically transmitted parasites has evolved the ability to distort the offspring sex ratios of their hosts. One such group of parasites are male-killing bacteria. Here we report the discovery of females of the ladybirdAnisosticta novemdecimpunctatathat produced highly female-biased offspring sex ratios associated with a 50% reduction in egg hatch rate. This trait was maternally transmitted with high efficiency, was antibiotic sensitive and was infectious following experimental haemolymph injection. We identified the cause as a male-killingSpiroplasmabacterium and phylogenetic analysis of rDNA revealed that it belongs to theSpiroplasma ixodetisclade in which other sex ratio distorters lie. We tested the potential for interspecific horizontal transfer by injection from an infectedA. novemdecimpunctataline into uninfected individuals of the two-spot ladybirdAdalia bipunctata. In this novel host, the bacterium was able to establish infection, transmit vertically and kill male embryos.

scholarly journals Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception

2007 ◽  
Vol 198 (1) ◽  
pp. 3-15 ◽  
Author(s):  
William H James
Keyword(s):  
Sex Ratios ◽  
Hormone Levels ◽  
Offspring Sex ◽  
Almost All

An attempt is made to summarize the evidence that the offspring sex ratios (proportions male at birth) of mammals (including man) are causally related to the hormone levels of both parents around the time of conception. Almost all of the cited studies were reported by non-endocrinologists. This being so, it would seem desirable to have comments of endocrinologists on this topic. The purpose of this article is to elicit such comment. Readers are requested to read the accompanying editorial (Clark & Davis 2008) to gain a better perspective of this hypothesis article.

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