A Study of the Heterochromatin ofAsellus Aquaticus(Crust. Isop.)

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Abstract
The constitutive heterochromatin of Asellus aquaticus can be differentially stained using the C-banding technique. It is present in the proximity of the NOs and, only rarely, in some of the other telomeres. Part of the A. aquaticus male population presents a heteromorphic chromosome pair due to the presence on one of the metacentric chromosomes of a heterochromatic area localized about half way along each arm. All the heterochromatin of the genome fluoresces brightly when stained with chromomycin A3 but remains dull after staining with quinacrine mustard. It seems therefore reasonable to argue that this is constituted by GC-rich DNA. An analysis of the late-labelling pattern reveals the presence of two chromosomes which replicate later than the constitutive heterochromatin.