The karyotypes of four species of Prot ra (Insecta, Apterigota) were determined. The diploid chromosome numbers range from eight to twenty. No sex chromosome could be morphologically detected. The chromosome centromeres are localized. The absence of males and the uncoupling of the oocyte chromosomes in Proturentomon minimum indicate a parthenogenetic way.
The chromosomes from 3 species of Collembola Onychiuridae belonging to the same genus, Onychiurus (Protafthorura), were analyzed. Onychiurus armatus and Onychiurus glebatus, with the highest chromosome number in Collembola (2n = 18), have morphologically different karyotypes. The diploid chromosome number of Onychiurus quadriocellatus is 2n = 16. There are not numerical differences between the two sexes. The taxonomic and evolutive significances of the unusual numerical differences within a collembolan...
The Lernaeid parasites of Carassius auratus, Cyprinus carpio, Lepomis gibbosus and Gambusia affinis, collected in Italy, belong to the same species: Lernaea cyprinacea L.. This is proved by the karyologic analysis (2n = 16 in all specimens) and by the variation of the anchor shape. There are no polyploid cells in L. cyprinacea embryos and sexual differences in chromosome number are lacking.
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