Genetic characterization of native and introduced populations of the neotropical cichlid genus Cichla in Brazil

A molecular phylogenetic analysis based on mitochondrial 16S ribosomal DNA and Control Region sequences from native and introduced populations was undertaken, in order to characterize the introduction of Cichla (peacock bass or tucunaré) species in Brazil. Mitochondrial DNA haplotypes found in introduced fish from Minas Gerais state (southeastern Brazil) clustered only with those from native species of the Tocantins River (Cichla piquiti and C. kelberi), thereby suggesting a single or, at most, few translocation acts in this area, even though with fish from the same source-population. Our study contributes to an understanding of the introduction of Cichla in regions of Brazil outside the Amazon basin, and adds phylogenetic data to the recently describe Cichla species, endemic from the Tocantins-Araguaia basin

Allometric larval growth of the bottom-dwelling catfish Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae)

ABSTRACT We investigated the early life growth pattern of pacamã, Lophiosilurus alexandri , a catfish endemic to the rio São Francisco basin, Brazil. Pacamã larvae were kept in a galvanized trough for 29 days after hatching. We collected approximately 10 larvae daily (total number = 285). We obtained from each specimen the total length (independent variable) and 11 other body measurements (dependent variables). We performed linear regressions on the log-transformed data to determine the growth pattern of the body measurements and the respective inflexion point on the growth curves. Except for trunk length, trunk width and yolk sac volume, the remaining body measurements showed a positive allometric growth coefficient up to the respective IP followed by a decrease in the rate of relative growth afterwards. Although trunk width presented a positive allometric growth, no significant inflexion point was detected. The dorsal-ventral head flattening seen in the adult pacamã was quickly expressed in the larvae as indicated by the large allometric growth of head width. Maxillary barbels showed the highest growth rate. The exceptionally high growth rates of eyes and maxillary barbels and the acquired ability to capture prey (as suggested by mouth length growth) strengthened the hypothesis of growth priorities in which the most essential organs develop first

Genetic characterization of native and introduced populations of the neotropical cichlid genus Cichla in Brazil

A molecular phylogenetic analysis based on mitochondrial 16S ribosomal DNA and Control Region sequences from native and introduced populations was undertaken, in order to characterize the introduction of Cichla (peacock bass or tucunaré) species in Brazil. Mitochondrial DNA haplotypes found in introduced fish from Minas Gerais state (southeastern Brazil) clustered only with those from native species of the Tocantins River (Cichla piquiti and C. kelberi), thereby suggesting a single or, at most, few translocation acts in this area, even though with fish from the same source-population. Our study contributes to an understanding of the introduction of Cichla in regions of Brazil outside the Amazon basin, and adds phylogenetic data to the recently describe Cichla species, endemic from the Tocantins-Araguaia basin

Testicular structure of three species of neotropical freshwater pimelodids (Pisces, Pimelodidae)

The testes structure of the following Siluriformes was studied: Pimelodus maculatus (Lacepède, 1803), Iheringichtys labrosus (Lütken, 1874) and Conorhynchos conirostris (Valenciennes, 1840). The testes of these species were dissected into cranial and caudal regions. The fringes of mature testes were counted and measured. Student's t-test was used to identify significant differences between fringe lengths of the two regions. To study the whole testes of each species in its resting and mature stage, testes were fixed in Bouin liquid for 6-8 hours and submitted to routine histological techniques. Standard histochemical techniques were used to detect carbohydrates and proteins. The testes of all species were paired and fringed organs. Histologically, cranial fringes of all species were spermatogenic with cells inside cysts at the same phase of development. Caudal fringes of C. conirostris were spermatogenic; while P. maculatus and I. labrosus showed caudal fringes only during secretion. Histochemically, neutral glycoproteins, acid glycoconjugates, acid carboxilates, sialomucines, and acid and sulfates glycoconjugates were detected in the caudal fringe secretions of P. maculatus; and neutral glycoproteins in I. labrosus. Significant differences between the fringe lengths of the cranial and caudal regions were found for all the species studied.<br>Estudou-se a estrutura testicular dos seguintes peixes Siluriformes: Pimelodus maculatus (Lacepède, 1803), Iheringichtys labrosus (Lütken, 1874) e Conorhynchos conirostris (Valenciennes, 1840). Os testículos foram dissecados e divididos anatomicamente em regiões cranial e caudal. As franjas dos testículos em maturação foram contadas e mediu-se o comprimento das mesmas. O teste t de Student foi utilizado para verificar diferenças significativas entre o comprimento das franjas das duas regiões. Para estudo histológico, testículos inteiros de cada espécie, em repouso e em maturação, foram fixados em líquido de Bouin por 6-8 horas e submetidos às técnicas histológicas de rotina. Utilizaram-se técnicas histoquímicas clássicas para detectar carboidratos e proteínas. Os testículos das espécies estudadas são órgãos pares e franjados. Histologicamente, as franjas da região cranial de todas as espécies são espermatogênicas, com células da linhagem em mesma fase de desenvolvimento contidas em cistos. As franjas da região caudal de C. conirostris são também espermatogênicas, enquanto P. maculatus e I. labrosus apresentam franjas caudais exclusivamente secretoras. Histoquímicamente detectou-se na secreção das franjas caudais de P. maculatus glicoproteínas neutras, glicoconjugados ácidos carboxilados, incluindo sialomucinas e glicoconjugados ácidos e sulfatados e em I. labrosus glicoproteínas neutras. Houve diferenças significativas entre o comprimento das franjas das regiões cranial e caudal para todas as espécies estudadas