C-heterochromatin in chromosomes of Ophiogomphus cecilia cecilia (Four.) (Anisoptera: Gomphidae) with notes on the sex chromosome origin in the species

Distribution of constitutive heterochromatin and nucleolar organizer regions in two species of family Gomphidae (Odonata: Anisoptera)

“…In the family Gomphidae, Pereplov et al [11] and Pereplov and Burgov [12] performed C-banding on Ophiogomphus cecilia cecilia and observed terminal Cbands in all the autosomes whereas X chromosome was the largest element of the set and possessed heterochromatic region at one of the ends and euchromatic part with three interstitial heterochromatic blocks on the other end. They concluded that the specific distribution Distribution of constitutive heterochromatin and nucleolar organizer regions has been studied for the first time on two gomphid species.…”

Meiotic Analysis of Gomphidae Species Sheds Light on the Large X Chromosome of the Family (Anisoptera, Odonata)

“…The other is a heteromorphic bivalent formed by the pairing of the neo-neo-Y with the neo-X and a univalent corresponding to the autosome B'. However, Ictinogomphus rapax and Ophiogomphus cecilia show 11 homomorphic bivalents and the large X chromosome at meiosis [7,9,17,19]. Only the characteristics of the 23 mitotic chromosomes are available for Gomphus graslini [11].…”

“…Later, Perepelov and Bugrov [17] proposed that the large X chromosome of Ophiogomphus cecilia originated from the fusion of the original X chromosome with two chromosomes of the same autosomal pair. This hypothesis seems unlikely as it would result in a genetic imbalance in both sexes: in females by the duplication of one chromosome pair and in males by the duplication of one chromosome.…”

“…The X chromosome is generally the smallest of the complement or the second smallest element after the m chromosomes. In contrast, it is the largest of the complement in some Gomphidae species and different theories have been postulated to explain its unusual size [7][8][9][10][11][12][13][14][15][16][17]. The sex chromosome systems may have originated from fusions or insertions, such as the neo-XY/neo-XX system and the multiple X 1 X 2 Y/X 1 X 1 X 2 X 2 system in Micrathyria ungulata [2,4,6,11,18].…”

“…C-banding revealed that most autosomes have heterochromatic blocks in both telomeric regions, which are either small or large and symmetric or asymmetric [19]. The X chromosome of males is entirely C-positive, and exhibits intermediate staining or possesses C-positive bands localised in the terminal or interstitial regions [6,15,[19][20][21][22][23][24].…”