Chromatin characteristics of spermatogenesis in the spider crab Lissa chiragra (Fabricius, 1775) (Majoidea, Epialtidae)

This article uses the male spider crab Lissa chiragra, collected from Ras el Tin beach on the Mediterranean Sea at Alexandria, Egypt between January and December 2017, as a model to isolate the histone variants, H2A, H2B, H3 and H4 from spermatozoal nuclei to detect the presence of their genes and the chromatin-associated proteins. The spermatozoal chromatin in Brachyura is electron dense. During spermiogenesis somatic histones and sperm nuclear basic proteins (SNBP’s) are replaced partially or totally by protamines or keratin proteins, which are rich in arginine and oxidized cysteine. Histones, which are part of the nucleosome, are classified according to their functional and structural criteria into H2A, H2B, H3 and H4. Amino acids of the purified chromatin associated proteins are analysed with high resolution liquid chromatography. The low condensation of the nucleus of the spermatozoa is due to a low proportion and modification of the chromatin-associated histones. The DNA is organized into nucleosomes but not in higher order structures due to acetylation of histone H4, but rather via regions of histone-free DNA.