Autosomale weibchendeterminierende Realisatoren beiArmadillidium nasatum (Isopoda terrestria)

Summary

Sex in the woodlouseArmadillidium nasatum ordinarily is determined by a gonosomal mechanism, the male being heterogametic. In a special strain, this mechanism is modified by autosomal female-determining factors which accumulated up to a certain quantity make an XY-individual develop into a female, against its gonosomal sex. A female of this kind produces an offspring with 1 ♀:3 ♂♂ sex ratio, one third of the males bearing two Y and therefore generating arrhenogenic offspring, i.e. consisting of males only. In contrary to a normal family (“family” means the whole inbreeding descendance over some generations originating from one female) the distribution of the sexes in the family of a female out of the arrhenogenic strain does no more show any relation to the ratio 1:1. The reason is discussed why a genetic system leading to aberrant sex-relations is maintained beside a gonosomal mechanism. The advantage of a high female rate for propagation seems to be at least one of the reasons. A high number of females can be advantageous as the lack of males is compensated by concentration of the animals and by the ability of the females to store sperms.