Chromosome banding in Amphibia. XVII. First demonstration of multiple sex chromosomes in amphibians: Eleutherodactylus maussi (Anura, leptodactylidae).
A cytogenetic study performed on a population of the South American leptodactylid frog Eleutherodactylus maussi revealed multiple sex chromosomes of the X1X1X2X2 female/X1X2Y male (= XXAA female/XXAY male) type. The diploid chromosome number is 2n = 36 in all females and 2n = 35 in most males. The multiple sex chromosomes originated by a centric fusion between the original Y chromosome and a large autosome. In male meiosis the X1X2Y (= XXAY) multiple sex chromosomes form a classical trivalent configuration. E. maussi is the first species discovered in the class Amphibia that is distinguished by a system of multiple sex chromosomes. Only one single male was found in the population with 2n = 36 chromosomes and lacking the Y-autosomal fusion. This karyotype (XYAA male) is interpreted as the ancestral condition, preceding the occurrence of the Y-autosome fusion.
Schmid
M
M
Department of Human Genetics, University of Würzburg, Federal Republic of Germany.
Steinlein
C
C
Feichtinger
W
W
D000818:Animals; D001001:Anura / Q000235:genetics*; D005075:Biological Evolution; D002871:Chromosome Banding; D005260:Female; D007621:Karyotyping; D008297:Male; D008540:Meiosis; D008938:Mitosis; D009867:Oogonia / Q000166:cytology; D012730:Sex Chromosomes; D013093:Spermatogonia / Q000166:cytology