Its amazing the lengths some males will go to just to maximise their chances of siring offspring. There are birds that, at the first whiff of scandal will peck at their partners? cloacae causing them to expel any vaginal contents. There are animals that will kill newborns whose paternity they suspect. Now it emerges that green-veined white butterflies (Pieris napi) go so far as to use non-fertile sperm to ?clog up the works? of female butterflies when they mate with them in order to put them off the idea of any further matings.
Penny Cook of Liverpool John Moores University, UK and Nina Wedell of the University of Stockholm, Sweden have found that the P.napi butterflies have two distinct types of sperm: fertile or ?euprene? sperm and the shorter, thinner, non-fertile, ?apyrene? sperm which lack nuclear material and represent around 90% of the total number of sperm in each ejaculate. As they explain in Nature [11 February], although both types are transferred to the female during mating (in a package known as a spermatophore) and both migrate to the site of sperm storage - the spermatheca - their effects once in place are actually quite different.
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