A new multiple sex chromosome system X1X1X2X2/X1Y1X2Y2in Siluriformes: cytogenetic characterization of Bunocephalus coracoideus (Aspredinidae).
We analyzed one Bunocephalus coracoideus population from the Negro River basin using cytogenetic techniques. The results showed a diploid number of 42 chromosomes in both sexes, with the karyotypic formula 4m + 14sm + 24a and fundamental number (FN) = 60 for females and the formula 5m + 14sm + 23a and FN = 61 for males, constituting an X1X1X2X2/X1Y1X2Y2multiple sex chromosome system. The constitutive heterochromatin is distributed in the pericentromeric regions of most of the chromosomes, except for the sex chromosomes, of which the X1, X2, and Y1chromosomes were euchromatic and the Y2chromosome was partially heterochromatic. 18S rDNA mapping confirmed the presence of nucleolar organizer regions on the short arms of the fifth chromosomal pair for both sexes. The 5S rDNA is present in the terminal regions of the short arms on the 2nd, 10th, and 12th pairs and on the X2chromosome of both sexes; however, we observed variations in the presence of these ribosomal cistrons on the Y1chromosome, on which the cistrons are pericentromeric, and on the Y2chromosome, on which these cistrons are present in the terminal portions of the short and long arms. Telomeric sequences are located in the terminal regions of all of the chromosomes, particularly conspicuous blocks on the 10th and 12th pairs and internal telomeric sequences in the centromeric regions of the 1st, 6th, and 9th pairs for both sexes. This work describes an new sex chromosomes system for the Siluriformes and increases our genetic knowledge of the Aspredinidae family.
Animal Genetics Laboratory, Biodiversity Coordination, National Institute of Amazonian Research, Av. André Araújo, 2936, Petrópolis, Campus II, Manaus, Amazonas, 69067-375, Brazil. milena_fro@hotmail.com.
Milena
M
Ferreira
Cytogenetics Laboratory, Biological Sciences Department, State University of Southwest Bahia, Jequié, Bahia, Brazil.
Caroline
C
Garcia
Biological Sciences Institute, Genetics Department, Amazonas Federal University, Manaus, Amazonas, Brazil.
Daniele Aparecida
DA
Matoso
Behavior Physiology and Evolution Laboratory, Biodiversity Coordination, National Institute of Amazonian Research, Manaus, Amazonas, Brazil.
Isac Silva
IS
de Jesus
Animal Genetics Laboratory, Biodiversity Coordination, National Institute of Amazonian Research, Av. André Araújo, 2936, Petrópolis, Campus II, Manaus, Amazonas, 69067-375, Brazil.
Eliana
E
Feldberg
D000818:Animals; D002397:Catfishes / Q000235:genetics*; D003582:Cytogenetics; D005260:Female; D006570:Heterochromatin; D017404:In Situ Hybridization, Fluorescence; D059785:Karyotype; D008297:Male; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D012730:Sex Chromosomes
D006570:Heterochromatin; D012337:RNA, Ribosomal, 18S; D012341:RNA, Ribosomal, 5S
5S rDNA; Banjo catfish; Constitutive heterochromatin; Multiple sex chromosomes
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