2025/01/01 by Luciano Cesar Pozzobon, Gustavo Akira Toma, Marcelo de Bello Cioffi +3 · 1 voice
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #Chromosomal and Genetic Variations #Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities #Plant Reproductive Biology
paper · doi:10.1139/gen-2024-0165
Our comprehension of avian karyotypes still needs to be improved, especially for Suliform birds. To enhance understanding of chromosomal evolution in this order, we conducted conventional and molecular cytogenetic analysis in five species, named Sula dactylatra, Sula leucogaster, Sula sula (Sulidae), Fregata magnificens (Fregatidae), and Nannopterum brasilianum (Phalacrocoracidae). The diploid chromosome number for S. dactylatra and S. leucogaster was established as 2 n = 76 in males, and 2 n = 75 in females, but S. sula displayed a karyotype of 2 n = 76 chromosomes in males. The disparity in diploid chromosome numbers between male and female Sula is due to a multiple sex chromosome system of the Z 1 Z 1 Z 2 Z 2 /Z 1 Z 2 W type. We propose that the emergence of this multiple-sex chromosome system resulted from a Robertsonian translocation involving the W chromosome and the smallest microchromosome. Fregata magnificens exhibited a diploid number 76 (2 n = 76), while N. brasilianum displayed a diploid number of 74 (2 n = 74) in both sexes. The ribosomal cluster was located in one microchromosome pair in S. dactylatra, S. leucogaster, S. sula, and F. magnificens and in four pairs in N. brasilianum. Our findings provide evidence of a conserved multiple-sex chromosome system within the Sula genus, shedding light on the high karyotype diversity in Suliformes.