A second case of multivalent meiotic configurations in diploid species of Anura

Lourenço, Luciana Bolsoni; Recco‐Pimentel, Shirlei Maria; Cardoso, Alisson C.

doi:10.1590/s1415-47572000000100024

Cited by 12 publications

(13 citation statements)

References 24 publications

(22 reference statements)

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“…In S. aequifasciatus and S. haraldi, the formation of the chromosomal chains is probably a result of multiple translocations of small terminal segments of chromosomal pairs ( Figure 5). Similar mechanisms have been proposed to explain the multivalent configuration in the meiotic cells of the anuran amphibians Physalaemus petersi and Eleutherodactylus binotatus (Lourenço et al, 2000;Siqueira Jr et al, 2004). In general, the hybridization and the presence of heterozygous translocations reduce population fitness due to the formation of unbalanced gametes.…”

Section: Discussionmentioning

confidence: 59%

Intriguing evidence of translocations in Discus fish (Symphysodon, Cichlidae) and a report of the largest meiotic chromosomal chain observed in vertebrates

et al. 2009

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As part of a program to understand the genetics of Amazonian ornamental fish, classical cytogenetics was used to analyze Symphysodon aequifasciatus, S. discus and S. haraldi, popular and expensive aquarium fishes that are endemic to the Amazon basin. Mitotic analyses in Symphysodon have shown some odd patterns compared with other Neotropical cichlids. We have confirmed that Symphysodon species are characterized by chromosomal diversity and meiotic complexity despite the fact that species share the same diploid number 2n ¼ 60. An intriguing meiotic chromosomal chain, with up to 20 elements during diplotene/ diakinesis, was observed in S. aequifasciatus and S. haraldi, whereas S. discus only contains typical bivalent chromosomes. Such chromosomal chains with a high number of elements have not been observed in any other vertebrates. We showed that the meiotic chromosomal chain was not sex related. This observation is unusual and we propose that the origin of meiotic multiples in males and females is based on a series of translocations that involved heterochromatic regions after hybridization of ancestor wild Discus species.

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Section: Discussionmentioning

confidence: 59%

Intriguing evidence of translocations in Discus fish (Symphysodon, Cichlidae) and a report of the largest meiotic chromosomal chain observed in vertebrates

et al. 2009

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“…The association of the NOR-bearing chromosomal arm of pair 1 with the long arm or pair 3 that carried the additional rDNA site reinforced the hypothesis of translocations as the main mechanism involved in this chromosomal rearrangement. Nevertheless, we cannot exclude the possibility that other mechanisms of dispersion, such as those discussed by Foote et al (1991), Schmid et al (1995) and Lourenço et al (1998Lourenço et al ( , 2000, are also involved, although they are less probable. These mechanisms include the transposition of mobile genetic elements, ribosomal cistron amplification and rDNA reinsertion errors during extra chromosomal amplification of ribosomal cistrons.…”

Section: Eleutherodactylus Binotatusmentioning

confidence: 79%

“…The lack of association of some chromosomes (pairs 7, 10 and 11, which remain as bivalents) with the multivalent rings could be related to the presence of interstitial heterochromatic regions in these chromosomes that could prevent pairing between homologous chromosomal arms. This hypothesis was proposed for Physalaemus petersi by Lourenço et al (2000), who described the second case of a multivalent meiotic configuration in Anura.…”

Section: Eleutherodactylus Binotatusmentioning

confidence: 94%

Cytogenetics of three Brazilian species of Eleutherodactylus (Anura, Leptodactylidae) with 22 chromosomes and re-analysis of multiple translocations in E. binotatus

2004

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In this paper, we provide a cytogenetic analysis of Eleutherodactylus guentheri, E. parvus and E. binotatus. All of the species had a diploid chromosomal number of 2n = 22. The karyotypes of E. guentheri and E. parvus were very similar and differed only slightly in the morphology of pair 2. These two species also had an NOR-bearing secondary constriction on the long arms of pair 6. The karyotype of E. binotatus differed from those of E. guentheri and E. parvus in the morphology and size of the chromosomes, in the number of chromosomal arms, in the NOR location (detected on the short arms of pair 1), and in the pattern of heterochromatin. These results reinforce the differences between E. guentheri and E. binotatus and support the existence of two species group. Five individuals of E. binotatus showed morphs for pairs 2 and 3. These morphs probably arose from the translocation of a segment from one chromosome of pair 3 to a homologue of pair 2. In addition, some mitotic metaphases of E. binotatus showed spontaneous chromosomal breaks which suggested that there were sites of fragility. Meiotic diakinesis showed multiple chromosomal rings, indicating the occurrence of multiple translocations, as previously reported by other investigators. These data suggest that, in addition to fission and fusion, other chromosomal rearrangements were probably involved in the differentiation of the karyotypes of these species of Eleutherodactylus, especially E. binotatus.

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“…arildae (with the participation of NORbearing chromosomes) might be explained by translocation events during evolution of the karyotype in these species. In anurans, this event is rare and has only been described for Eleutherodactylus binotatus [Beçak and Beçak, 1974;Siqueira et al, 2004] and Engystomops petersi [Lourenço et al, 2000]. In both cases, the presence of these rings was apparently related to the rearrangement of multiple heterozygous translocations that resulted in morphological alterations in the chromosomes involved in the ring.…”

Section: Discussionmentioning

confidence: 99%

NOR Dispersion, Telomeric Sequence Detection in Centromeric Regions and Meiotic Multivalent Configurations in Species of the <i>Aplastodiscus albofrenatus</i> Group (Anura, Hylidae)

Carvalho

García

Recco‐Pimentel

2009

Cytogenet Genome Res

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In the present study, we examined the chromosome number and morphology, heterochromatin pattern, and location of the nucleolar organizer region (NOR) and telomeric sequences in Aplastodiscus albofrenatus, A. arildae, A. ehrhardti and A. eugenioi in order to cytogenetically characterize the Aplastodiscus albofrenatus group. The 4 species analyzed in this study had diploid numbers of 2n = 22 and very similar chromosome morphology. These species could be differentiated based on the distribution and amount of heterochromatin and the location of the nucleolar organizer region (NOR). Six of the 8 A. albofrenatus individuals had an NOR polymorphism previously unknown in anurans since only one of the homologs of pairs 1 and 7 was stained. In the other 2 specimens, the NOR occurred on both homologs of pair 7. In A. ehrhardti, pairs 6 and 10 were stained by the AgNOR technique, but only pair 6 was confirmed by in situ hybridization. The NOR was located on pair 10 in A. arildae and on pair 7 in A. eugenioi. In A. albofrenatus and A. arildae, multivalent rings involving NOR-containing chromosomes were observed during prophase I of meiosis. The telomeric probe identified the telomeres in all species and also centromeric regions in the chromosomes of A. albofrenatus and A. arildae, which were coincident with centromeric heterochromatin. The conserved chromosomal morphology seen mainly in the first 7 pairs among species of the A. albofrenatus group suggests that all of these species probably originated from a common ancestral karyotype and that chromosomal rearrangements resulted in karyotype differentiation, with changes in NOR location, as well as telomeric and heterochromatin dispersal.

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A second case of multivalent meiotic configurations in diploid species of Anura

Cited by 12 publications

References 24 publications

Intriguing evidence of translocations in Discus fish (Symphysodon, Cichlidae) and a report of the largest meiotic chromosomal chain observed in vertebrates

Intriguing evidence of translocations in Discus fish (Symphysodon, Cichlidae) and a report of the largest meiotic chromosomal chain observed in vertebrates

Cytogenetics of three Brazilian species of Eleutherodactylus (Anura, Leptodactylidae) with 22 chromosomes and re-analysis of multiple translocations in E. binotatus

NOR Dispersion, Telomeric Sequence Detection in Centromeric Regions and Meiotic Multivalent Configurations in Species of the <i>Aplastodiscus albofrenatus</i> Group (Anura, Hylidae)

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