Cytogenetic and morphometric differences in populations of Astyanax "scabripinnis" (Pisces, Characidae) from Maringá region, PR, Brazil

Abstract

A cytogenetic and morphometric study of four populations of characid fish assigned to the "complex" of Astyanax scabripinnis originating from three riverine basins, namely Ivaí (populations A and B), Paranapanema (C) and Paraná (D), was carried out. Karyological analysis showed the diploid chromosome number 2n = 48 for population B and 2n = 50 for the remaining populations. All populations under study differed in the composition of karyotypes and C-banding patterns. Canonical variable analysis used to assess the morphometric data revealed that 1) the four populations under study were entirely discriminated from each other and 2) the coefficients that most contributed to this pattern were standard length, rostrodorsal distance, eye diameter and snout length. The results indicate that the differences in karyotypes were paralleled by the morphological differentiation of the populations under study and contributed to the problem of systematics of A. scabripinnis "complex".<br>Foram realizados estudos citogenéticos e morfométricos de quatro populações de peixes characídeos, designados de" complexo" de Astyanax scabripinnis, pertencentes a três bacias hidrográficas diferentes: bacia do Ivaí (populações A e B), do Paranapanema (população C) e do Paraná (população D). A análise cariotípica mostrou um número diplóide de 2n = 48 cromossomos para a população B e de 2n = 50 cromossomos para as demais populações. Todas as populações analisadas diferiram na composição cariotípica e no padrão de banda C. A análise de variável canônica, aplicada aos dados morfométricos, revelou que: 1) as quatro populações estudadas foram totalmente discriminadas entre si, e 2) os coeficientes que mais contribuíram para isto foram o comprimento padrão, distância rostro-dorsal, diâmetro do olho e comprimento do focinho. Portanto, estes resultados indicam que as diferenças cariotípicas foram acompanhadas pelas diferenças morfológicas nas populações e contribuíram para o problema da sistemática do "complexo" A. scabripinnis

Occurrence of a Metacentric Macrochromosome B in Different Species of the Genus Astyanax (Pisces, Characidae, Tetragonopterinae).

“…A complementary study in the Campos do Jorddo region showed different frequencies for this chromosome in different populations of A. scabripinnis, and confirmed a high frequency of carriers among specimens from the Pedras stream (about 79%) and lower frequencies among specimens from the Casquilho (39%) and the Perdizes (22%) streams, with a distortion in the sex ratio associated with the presence of Bs (Vicente et al 1996). On the other hand Rocon-Stange and Almeida-Toledo (1993) and Mizoguchi and Martins-Santos (1997) reported a variation of 1 to 4 microchromosomes B in some other populations of A. scabripinnis.…”

“…Maistro et al (1992), studying A. scabripinnis from another locality (Araqua river, Botucatu, Sdo Paulo State, Brazil), identified a B chromosome with a similar size and shape, but with a lower frequency about 27% and, with only females being carriers. Mizoguchi and Martins-Santos (1997), observed that this type of B chromosome was present only in 19% of the specimens from the Yukatan river (Maringa, Parana State, Brazil), and again restrict to females. A complementary study in the Campos do Jorddo region showed different frequencies for this chromosome in different populations of A. scabripinnis, and confirmed a high frequency of carriers among specimens from the Pedras stream (about 79%) and lower frequencies among specimens from the Casquilho (39%) and the Perdizes (22%) streams, with a distortion in the sex ratio associated with the presence of Bs (Vicente et al 1996).…”

“…2c). Cytogenetic studies on A. scabripinnis have been intensified over the past years (Moreira-Filho and Bertollo 1991a, Maistro et al 1998, Mizoguchi andMartins-Santos 1998, among others). Several populations of this species have a large metacentric B chromosome, similar in size to the first pair in the complement (Fig.…”

“…For the genus Astyanax in particular, these chromosomes have been described in A. scabripinnis (Salvador and Moreira-Filho 1992, Maistro et al 1992, Fauaz et al 1994, Souza and Moreira-Filho 1995, Vicente et al 1996, Mizoguchi and Martins-Santos 1997 and A. eigenmanniorum (Stripecke et al 1985). B chromosomes are "additional dispensable chromosomes that are present in some individuals from some populations in some species, which have probably arisen from the A chromosomes but that follow their own evolutionary pathway" (Camacho 1993).…”

“…Among the known examples in fish, some cases are sporadic, as in Apareiodon piracicabae and Oligossarcus pintoi (Falcao et al 1984). On the other hand, there are several situations in which these chromosomes are frequent in the populations, as in Rhamdia hilarii (Fenocchio and Bertollo 1990), Prochilodus lineatus (=scrofa) (Pauls and Bertollo 1993) and Astyanax scabripinnis (Salvador and Moreira-Filho 1992, Maistro et al 1992, Souza and Moreira-Filho 1995, Vicente et al 1996, Mizoguchi and Martins-Santos 1997. They can vary widely in size, ranging from macrochromosomes as in Astyanax scabripinnis (Salvador andMoreira-Filho 1992, Maistro et al 1992) to microchromosomes as in Moenkhausia sanctaefilomenae (Foresti et al .…”