First description of multivalent ring structures in eutherian mammalian meiosis: new chromosomal characterization of Cormura brevirostris (Emballonuridae, Chiroptera)

Abstract

Twelve specimens of the bat Cormura brevirostris (Emballonuridae: Chiroptera) were collected from four localities in the Brazilian Amazon region and analyzed by classical and molecular cytogenetics. The diploid number and autosomal fundamental number were as previously reported (2n = 22 and FNa = 40, respectively). Fluorescence in situ hybridization using rDNA probes and silver nitrate technique demonstrated the presence of two NOR sites and the presence of internal telomeric sequences at pericentromeric regions of all chromosomes with exception of Y. Based on meiotic studies and chromosome banding we suggest that the sex chromosome pair of C. brevirostris was equivocally identified as it appears in the literature. Meiotic analysis demonstrated that at diplotene-diakinesis the cells had a ring conformation involving four chromosome pairs. This suggests the occurrence of multiple reciprocal translocations among these chromosomes, which is a very rare phenomenon in vertebrates, and has never been described in Eutheria.

Meiotic analyses show adaptations to maintenance of fertility in X1Y1X2Y2X3Y3X4Y4X5Y5 system of amazon frog Leptodactylus pentadactylus (Laurenti, 1768)

“…Thus, when perform synapses during meiotic cycles consist of various types of multivalent associations, ranging from simple trivalent to complex forms, involving several karyotype elements 5 – 7 . These systems have also been observed in other animals, including bats 6 – 8 , rodents 3 , birds 9 , fish 10 , lizards 11 , beetles 12 , butterflies 13 , termites 14 , spiders 15 and scorpions 16 .…”

Physical mapping of repetitive DNA suggests 2n reduction in Amazon turtles Podocnemis (Testudines: Podocnemididae)

“…Chromosome mapping of telomeric sequences has been widely used to identify chromosomal rearrangements between the karyotypes of different vertebrate lineages, including various mammals [ 12 – 15 ] amphibians [ 16 , 17 ] and fishes [ 18 , 19 ]. In diverse organisms, the presence of interstitial telomeric sequences, often in association with heterochromatic regions, appear to represent remnants of chromosomal rearrangements that have contributed to reorganizing the genomic architecture and providing new chromosomal forms during evolution [ 17 , 20 – 24 ].…”

Chromosomal Evolution in Chiroptera

“…An impressive observation was recently made in Cormura brevirostris (2n = 22) from Brazil. In this species, 8 autosomes showing only monobrachial homology and the presence of a multivalent ring in male meiosis [ 70 ] may indicate chromosomal evolution by multiple simultaneous whole arm translocation events, a novelty for Eutheria. Based on their wide range of chromosomal numbers and divergences in the G-banding pattern, emballonurids can be considered a group with considerable amounts of karyotypic evolution.…”