Genetic variability of wild and captivity populations of Colossoma macropomum (Cuvier, 1818) / Variabilidade genética de populações selvagens e de cativeiro de Colossoma macropomum (Cuvier, 1818)

Tambaqui (Colossoma macropomum) is among the most important fish species of the Amazon and one of the most cultivated in Brazil. In the present work we have evaluated the genetic variability of wild and captivity populations of C. macropomum. Enzymatic markers were used to estimate the genetic variability of 41 specimens from a wild group; and 30, 33 and 45 from three captivity groups, which came from Pentecostes (Ceará State), Jaboticabal (São Paulo State) and Itacoatiara (Amazonas State), respectively. Nine isoenzymic systems were used to evaluate the genetic variability of these populations. Using zimogram data we obtained the polymorphism level, allele number, allelic frequency, observed and expected heterozigosity, Wright F statistics (FIS, FST), genetic distance, level of similarity and group analysis. The isoenzymic data showed that, from the nine systems, six presented polymorphic loci (Fbp-2, G6pdh-2, G6pdh-3, Pgi-1, Pgi-2 and Pgm-1). The populations from Pentecostes and Jaboticabal presented loss of genetic variability and low heterozigosity, compared to the wild population and to the artificial population acquired at Itacoatiara fish farm. Based on these results and on fish farmer information we could consider the population from Itacoatiara as recently derived from a wild population. Concluding, we suggest that the artificial populations of tambaqui, which contain animals originated from this funding population at Pentecostes, should be renewed with the introduction of a new group of individuals with genetic variability equivalent to the wild population.

O tambaqui é uma espécie de peixe bastante importante na região amazônica e uma das espécies mais cultivadas no Brasil. O objetivo deste trabalho foi avaliar a variabilidade genética do Colossoma macropomum de cativeiro e selvagem, utilizando marcadores isoenzimáticos. Utilizamos 41 indivíduos de uma população da natureza e 30, 33 e 45 de populações de cativeiro de Pentecoste, Jaboticabal e Itacoatiara, respectivamente. Nove sistemas isoenzimáticos foram utilizados para verificar a variabilidade genética do tambaqui, bem como os níveis de polimorfismos, números de alelos, freqüências alélicas, heterozigosidade observada e esperada, estatística F de Wright (FIS e FST), distância e similaridade genética, e análise de agrupamento. Das nove isoenzimas analisadas apenas seis sistemas apresentaram polimorfismo (Fbp-2, G6pdh-2, G6pdh-3, Pgi-1, Pgi-2 and Pgm-1). Verificamos que as populações de Pentecostes e Jaboticabal estão com falta de heterozigotos e apresentam-se estruturadas geneticamente em relação às populações de Itacoatiara e da Natureza que apresentam excesso de heterozigotos e não são estruturadas. Concluímos que os indivíduos de Itacoatiara são provenientes de populações selvagens e sugerimos que se realize uma renovação dos plantéis de tambaqui de Pentecostes e Jaboticabal, com o intuito de recuperar a variabilidade genética perdida.

Metabolic adjustments in Satanoperca aff. jurupari (Perciformes: Cichlidae)

In this paper, we describe the enzyme levels and isozyme distribution in skeletal and heart muscle of Satanoperca aff. jurupari, (Cichlidae, subgroup Geophaginae). LDH and CS were measured in skeletal and heart muscle. Starch gel electrophoresis was used to determine the isozyme/allozyme patterns in different tissues; LDH, MDHs, PGM, PGI, ADH, G-6-PDH and SOD were screened for the numbers of loci, presence of alleles, and tissue specificity. The LDH/CS ratio in heart and skeletal muscle were 173.36 and 6.1, respectively, indicating anaerobic metabolism in the former and aerobic metabolism in the latter muscle. No inhibition by pyruvate (based on the ratios of LDH activity with 1 mM and 10 mM pyruvate) was detected in heart and skeletal muscle, indicating the presence of physiological plasticity in heart muscle. The heart can cope with anaerobic metabolism for short periods of hypoxia such as occurs in nature. Isozyme patterns for most of the enzymes analyzed were similar to the general patterns for advanced teleosts. S. aff. jurupari had no reduced LDH-B* expression in heart muscle, but the, MDHs-B* locus was duplicated, as reported for most Amazon cichlids species. Only three out of the 13 loci analyzed (PGM, PGI and SOD) were variable. These results are consistent with the metabolic profile and life style of the most cichlids. A low genetic variability may be a counterpart for plasticity, and may be guaranteed by the regulation of invariable structural genes