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Citogenética clássica e molecular de Ctenus spp. (Ctenidae, Araneae) provenientes de Manaus, AM
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Instituto Nacional de Pesquisa da Amazônia - INPA
Resumo
The Ctenidae family is composed of spiders with nocturnal and, often, aggressive behavior. This group is receiving high attention due to possibilities of ecological and medical field studies, but have few publications with cytogenetic data. The spiders in this group so far, have showed 2n = 26T + X1X20 for most cases, but some species have 2n = 26T + X1X2X30. The constant number of autosomes and the variation in the number of sex chromosomes allows the possibility of cytogenetic studies that may be useful to understand the mechanisms of chromosome evolution in this group. A classical and molecular (using 18S rDNA probes) cytogenetic characterization was performed using the species Ctenus amphora (Mello-Leitão 1930), C. crulsi (Mello-Leitão, 1930) and C. villasboasi (Mello-Leitão 1949). The three species presented a similar karyotype, with 2n = 26T + X1X20 for males and sexual chromosomes showing heteropicnosis. The results for 18S rDNA mapping revealed gene sites in the terminal region of a chromosomal pair for the three species, with
polymorphism in a C. crulsi individual, which showed sites in two pairs. The distribution pattern of constitutive heterochromatin was characteristic for the genus, with bands in
the centromeric region of all the chromosomes. The number of Nucleolar Organizer
Regions (NORs) was in agreement with the rDNA sites evidenced by the molecular
technique, with marks in a chromosomal pair for C. amphora and C. crulsi, while C. villasboasi presented NORs only in pachytenes cells. The results obtained demonstrate a pattern for the genus regarding the number of chromosomes and the sexual chromosomal system and reinforce theories that describe the fusion of chromosomes as an evolutionary tendency for the group.
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