Cytogenetic analysis of two locariid species (Teleostei, Siluriformes) from Iguatemi River (Parana River drainage) in Brazil

Abstract

Fishes of the Loricariidae family, known as “cascudos”, constitute an endemic group in Neotropical freshwaters. In this study, were cytogenetically examined two species of Loricariidae (Pterygoplichthys anisitsi Eigenmann & Kennedy, 1903 and Farlowella amazonum (Günther, 1864) belonging to Hypostominae and Loricariinae subfamilies respectively) from Iguatemi River. Our study provide the first description regarding C-band and fluorochromic analysis in Farlowella amazonum. In Farlowella amazonum, diploid number was 58 chromosomes, with single Ag-NOR and heterochromatic blocks in centromeric regions of some chromosomes and large subtelomeric blocks were evidenced on the long arm of the pair 27, being this region CMA3+/DAPI-. The Pterygoplichthys anisitsi showed diploid number equal 52 chromosomes, with single Ag-NOR and heterochromatic blocks in centromeric and telomeric regions of some chromosomes and conspicuous large telomeric blocks on the long arm of the pair 10, being this region CMA3+/DAPI-. The results show that karyotype formula is nonconservative in Pterygoplichthys anisitsi and Farlowella amazonum.

Chromosomal Diversity in Two Allopatric Populations of Farlowella hahni Meinken 1937 (Teleostei: Siluriformes): Cytogenetics and Cytochrome b Analyses

“…A number of chromosomal rearrangements, such as pericentric inversions and/or deletions are found in the genomes of F. hahni analyzed in this study, given that, although they have the same 2n, the FN value and the karyotypes are different, which the separation geographic and reduced vagility of species, which may lead to the formation of small isolated populations, may have facilitated the establishment of this karyotype variation due to the restriction of gene flow between them. In the Farlowella species analyzed up to now, the nucleolar organizer region (NOR) phenotype is simple, as confirmed by the 18S rDNA probe as shown in Fernandes et al 8,9 and Marajó et al, 10 and the present study. In the karyotype of F. hahni under study, whereas in those of F. schreitmuelleri 10 and F. hahni previous studies, 8,9 the NORs are found on the long arms of the first acrocentric pair, which appears to be a conserved pattern in this genus, except in Farlowella cf.…”

“…In the Farlowella species analyzed up to now, the nucleolar organizer region (NOR) phenotype is simple, as confirmed by the 18S rDNA probe as shown in Fernandes et al 8,9 and Marajó et al, 10 and the present study. In the karyotype of F. hahni under study, whereas in those of F. schreitmuelleri 10 and F. hahni previous studies, 8,9 the NORs are found on the long arms of the first acrocentric pair, which appears to be a conserved pattern in this genus, except in Farlowella cf. amazonum 10 the NOR site is located in the pericentromeric region of the long arms of the first metacentric pair.…”

“…A diploid number of 58 chromosomes has been identified invariably in Farlowella species, including Farlowella cf. amazonum, F. schreitmuelleri 10 and different F. hahni po-pulations as shown in Fernandes et al 8,9 and the present study. A number of chromosomal rearrangements, such as pericentric inversions and/or deletions are found in the genomes of F. hahni analyzed in this study, given that, although they have the same 2n, the FN value and the karyotypes are different, which the separation geographic and reduced vagility of species, which may lead to the formation of small isolated populations, may have facilitated the establishment of this karyotype variation due to the restriction of gene flow between them.…”

“…amazonum and F. schreitmuelleri, which have showed a diploid number of 58 chromosomes, but with minor karyotype differences between three species analyzed. [8][9][10] In Loricariinae, physical mapping of 18S rDNA were detected in three chromosomes for Rineloricaria lanceolata, 11 in two chromosomes for Harttia loricariformis 12 and individual females of Harttia punctata, 13 in one chromosome of individual males H. punctata. 13 Physical mapping of 5S rDNA in this subfamily were detected in H. punctata, located in two chromosomes for males or females.…”

First cytogenetic characterization ofLoricaria simillima(Loricariidae, Siluriformes) from Paraná River (Argentina) with emphasis in cytotaxonomy ofLoricaria

“…According to Takagui et al (2014) the presence of a few heterochromatic blocks, mainly in the pericentric region, is a remarkable feature of armored catfishes of the subfamily Loricariinae, present in species of the basal genus Harttia (Kavalco et al 2005;Blanco et al 2012) as well as in the derived genus Rineloricaria (Rosa et al 2011;Porto et al 2014b). The exceptions to this pattern are Farlowella amazonum (Fernandes et al 2015) and Loricaria cataprhacta (Porto et al 2014a), which have additional conspicuous terminal heterochromatin blocks in different chromosomes.…”