First constitutive heterochromatin characterization and Karyotype of white stork Ciconia ciconia (Aves: Ciconiidae)

Abstract

The karyotype and constitutive heterochromatin pattern of the white stork Ciconia ciconia samples obtained from Manzala lake, Dimiaat, Egypt was described. Somatic cells of Ciconia ciconia samples have diploid number 2n= 68 chromosomes. Out of 68 chromosomes, 11 pairs including sex chromosomes were macrochromosomes and the remaining pairs were microchromosomes. Of the 11 macrochromosome pairs, no.1, 2, 4 and 5 were submetacentric and pairs no. 6, 7 and 8 were described as metacentric. In addition, the autosome pair no.3 was subtelocentric, while autosome pair no.9 was acrocentric. Also, the sex chromosome Z represents the fourth one in size and it was classified as submetacentric while, W chromosome appeared as medium size and was acrocentric. Furthermore, C-banding pattern (constitutive heterochromatin) revealed variation in their sizes and occurrence between macrochromosomes. Pairs no. 7 and 8 of autosomes exhibited unusual distribution of heterochromatin, where they appeared as entirely heterochromatic. This may be related to the origin of sex chromosomes Z and W. However, there is no sufficient evidence illustrate the appearance of entirely heterochromatic autosomes. Therefore, there is no available cytogenetic literature that describes the C-banding and karyotype of Ciconia Ciconia, so the results herein are important and may assist in cytogenetic study and evolutionary pattern of Ciconiiformes.

Cytotaxonomy and Molecular Analyses of Mycteria americana (Ciconiidae: Ciconiiformes): Insights on Stork Phylogeny

“…Although cytogenetic data concerning Ciconiidae are still scarce, it is clear that this family has interesting karyotypic features, given the great diversity in diploid numbers (2n = 52 to 2n = 78) and evidence of chromosomal rearrangements with potential phylogenetic value [ 8 , 37 ]. In this sense, considering that chromosomal rearrangements play a key role in speciation and genome evolution, whole chromosome probes provide important insights into the karyotypical diversification of birds [ 38 , 39 , 40 ].…”

“…This pattern is similar to other groups of birds [ 39 , 41 , 42 ]. However, in Ciconia ciconia , the only species of Ciconiidae with a C-banding pattern, pairs 7, 8, and chromosome W seemed to be entirely heterochromatic [ 37 ].…”

“…Compared with the ancestral avian karyotype, it is possible to observe that the decrease in diploid numbers is related to a concomitant decrease in the number of microchromosomes, while macrochromosomes maintain similarity in number and morphology [ 8 , 22 , 37 ]. Although studies indicate that most bird species maintain evolutionary stability in their microchromosomal organization, in some orders (for example, Falconiformes, Psittaciformes, Cuculiformes, Trogoniformes, and Suliformes), fusions involving microchromosomes have been detected, resulting in small/medium biarmed chromosomes and consequent decrease in the diploid number [ 23 , 24 , 29 , 43 ].…”