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Previous issue date: 2016-08-26 / Fundação de Amparo à Pesquisa do Estado do Amazonas - FAPEAM / Currently, marsupials are the second largest mammals living family. The groups evolutionary history
is linked to the geological history of the continent and in South America, they are represented mainly
by Didelphidae family. This family is the only present in the Amazon and in the rest of Brazil.
Marsupial cytogenetic characterization shows a conservation of diploid numbers ranging from 10 to
32 chromosomes, and in didelphids are known karyotypes 14, 18 and 22 chromosomes. In this
context, molecular cytogenetic allows for new inferences about the chromosomal evolution, supplying
additional characters to analyze, for example, mapping repetitive regions of the genome. In this paper
we map repetitive elements in species didelphids collected in 13 new locations in the Amazon in
unexplored regions, seeking to understand evolutionary patterns of karyotypes. In all were analyzed
194 individuals of 16 species featured in conventional staining, band C, Ag-RON and FISH with
probes DNAr18S, telomeric and transposable element LINE-1. We observed variation on the X
chromosome, the distribution of heterochromatin and mapping sequences of 18S ribosomal DNA and
telomeric sequences. The main variation found in the position of the centromere was the X
chromosome of C. lanatus and Marmosa murina. Geographically, the different types of X, both
species showed a segregation between eastern and western Brazil, with contact in the central
Amazon. For species Marmosops spp. two patterns of X were evidenced by the C-band technique,
but less obvious geographical distribution. The nucleolar organizer regions were confirmed by 18S
rRNA gene probe in all species except the marking of the Y chromosome Monodelphis brevicaudata.
The distribution of this marker showed only variable in Marmosa genre. Considering RON simple as a
character plesiomorphic conclude that the species of the genus Didelphis and Marmosa evolved
independently for multiple system. Marsupials are considered chromosomally conservative, however,
given the current state of knowledge to this group, inter variations and intraspecific are observed and
this is due to the expansion of the sample and the application of more accurate techniques,
suggesting the presence of chromosomal rearrangements in evolution this animal group. Regarding
the telomeric sequences, 11 species were analyzed and compared the presence of interstitial
telomeric sequences (ITSs) with the distribution of the C band and found that STIs are coincident with
heterochromatin blocks. Of the 11 species examined, only 5 had STIs, all within the centromeric
heterochromatin region. The presence of STIs was constant on the X chromosome of Marmosa
individuals and murine variable in the other species. We believe that the variable presence of STIs is
a particular characteristic of each lineage. Our results support the inference that such sequences can
not always be interpreted as a consequence of chromosomal rearrangement. Finally, we map the
LINE-1 retroelement to five species of copies: Caluromys philander, Gracilinanus emiliae, Marmosa murina, Marmosa demerarae and Didelphis marsupialis. The markings are shown scattered all
chromosomes, with no preference for specific chromosome regions, or even the X chromosome, as
reported in the literature for other marsupials. The most informative variations were in the morphology
of the X chromosome, which verified the existence of geographic patterns and are possibly related to
different species, showing that chromosomal variation has relation to the diversification of species.
Markers of repetitive sequences (18S, telomere and L1) showed variations possibly be related to
more recent events of speciation. / Os marsupiais sulamericanos estão representados principalmente pela família
Didelphidae considerada conservada cariotipicamente. No presente trabalho mapeamos
elementos repetitivos em 194 indivíduos, representando 16 espécies de didelfídeos,
coletadas em 13 localidades ainda não exploradas, do ponto de vista científico, na
Amazônia, para verificar possíveis padrões de evolução cariotípica. Para isso foram
utilizados métodos citogenéticos clássicos e moleculares. Variações no cromossomo X,
na distribuição da heterocromatina e no mapeamento de sequências de DNA ribossomal
18S e sequências teloméricas foram registradas. A principal variação foi na posição do
centrômero do cromossomo X de Caluromys lanatus e de Marmosa murina. Os diferentes
tipos de cromossomos X, de ambas espécies, mostraram uma separação em termos
geográficos entre leste e oeste do Brasil, com contato na Amazônia central. Para as
espécies de Marmosops spp., dois padrões de X foram evidenciados pelo método de
banda C, porém não foram separados geográficamente. As regiões organizadoras de
nucléolo foram confirmadas pelas sondas de DNAr 18S em todas as espécies, exceto a
marcação do cromossomo Y de Monodelphis brevicaudata. A distribuição desse marcador
se mostrou variável apenas no gênero Marmosa. Considerando a RON simples como um
caráter plesiomórfico sugerimos que as espécies do gênero Marmosa e Didelphis
marsupialis evoluíram independentemente para o sistema múltiplo. Em relação às
sequências teloméricas, 11 espécies foram analisadas e cinco apresentaram ITSs, todas
dentro da região de heterocromatina centromérica. A presença de ITS foi constante no
cromossomo X de indivíduos de Marmosa murina e variável nas demais espécies.
Acreditamos que a presença variável das ITSs seja uma característica particular de cada
linhagem. O retroelemento LINE-1 foi mapeado em exemplares de cinco espécies:
Caluromys philander, Gracilinanus emiliae, Marmosa murina, Marmosa demerarae e
Didelphis marsupialis. As marcações se mostraram dispersas por todos os cromossomos,
não havendo preferência por regiões específicas do cromossomo, nem mesmo pelo
cromossomo X. A variação do cromossomo X e os padrões de distribuição dos elementos
repetitivos podem ser reflexo dos eventos de especiação ocorridos nos didelfídeos.
Identifer | oai:union.ndltd.org:IBICT/oai:localhost:tede/2219 |
Date | 26 August 2016 |
Creators | Silva, Carlos Eduardo Faresin e |
Contributors | Feldberg, Eliana, Silva, Maria Nazareth Ferreira da |
Publisher | Instituto Nacional de Pesquisas da Amazônia, Genética, Conservação e Biologia Evolutiva (GCBEv), INPA, Brasil, Coordenação de Pós Graduação (COPG) |
Source Sets | IBICT Brazilian ETDs |
Language | Portuguese |
Detected Language | English |
Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
Format | application/pdf |
Source | reponame:Biblioteca Digital de Teses e Dissertações do INPA, instname:Instituto Nacional de Pesquisas da Amazônia, instacron:INPA |
Rights | http://creativecommons.org/licenses/by-nc-nd/4.0/, info:eu-repo/semantics/openAccess |
Relation | -5829914500254207356, 600, 600, 600, 3806999977129213183, -4671505905809893211 |
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