Segregational mechanisms of sex chromosomes in Spongilla-flies (Neuroptera: Sisyridae).
Evolutionary loss of the Y chromosome has occurred in Climacia areolaris (Hagen) of the neuropteran family Sisyridae. The diploid set comprises 6 pairs of autosomes, plus 2 X chromosomes in the female and 1 X in the male. The Y is retained in Sisyra vicaria (Walker) of the same family: its chromosome number is 14 in both sexes including 2X chromosomes in the female and 1X plus Y in the male. Two alternative pathways for the segregation of the sex chromosomes-distance segregation and sex bivalent formation-co-exist in the latter species in a ratio of approximately 1 to 6; the possible phylogenetic significance of this feature is discussed.
D000818:Animals; D012734:Disorders of Sex Development; D005260:Female; D007313:Insecta / Q000166:cytology* / Q000254:growth & development; D008297:Male; D008540:Meiosis; D010802:Phylogeny; D012730:Sex Chromosomes; D013737:Testis / Q000166:cytology