Drift of ichthyoplankton in two channels of the Paraná River, between Paraná and Mato Grosso do Sul states, Brazil

Analysis of drift of ichthyoplankton in two channels in the River Paraná, Brazil, were made. Sampling was undertaken from October 1995 to April 1996 during nychthemeral cycles. Water samples were collected to determine several environmental variables. Eggs densities largely differed to layers, times of day and months. In both the channels, highest occurrence of eggs was detected between January and March; greater concentrations at the bottom, during night. With regard to larvae, densities were significantly different in channels, times of days and months. Maximum occurrences were seen in the right channel, in both layers, with largest capture between January and March. Surface of the both channels presented highest density of larvae during night. Water temperature, electrical conductivity and flux velocity were different in the two channels, however, these variables and larvae density didn't showed correlations. This indicates that there was another possible factor, might be influencing the distribution of ichthyoplankton.<br>Este trabalho teve por objetivo analisar a deriva do ictioplâncton em dois canais com diferentes condições de topografia e velocidade de fluxo, entre os estados do Paraná e Mato Grosso do Sul (Brasil). As amostragens foram realizadas no período de outubro de 1995 a abril de 1996, durante ciclos nictemerais. Amostras de água foram coletadas para determinação de algumas variáveis ambientais. A densidade de ovos diferiu significativamente entre os estratos, horários e meses; sendo que em ambos os canais, as maiores ocorrências de ovos foram verificadas entre janeiro e março, com maiores concentrações no fundo durante o período noturno. Com relação as larvas, as densidades diferiram entre os canais, horários e meses. As maiores ocorrências foram observas no canal direito, em ambos estratos, com maior período de captura entre janeiro e março. A superfície dos canais apresentou as maiores densidades de larvas durante o período noturno. A temperatura da água, condutividade elétrica e velocidade de fluxo foram diferentes entre os canais, entretanto, essas variáveis e a densidade de larvas não mostraram correlação, indicando que possivelmente outro fator, esteja influenciando a distribuição do ictioplâncton neste ambiente

Early ontogeny of Clarias gariepinus (Siluriformes, Clariidae) and aspects of its invasion potential in natural freshwater environments - doi: 10.4025/actascibiolsci.v35i3.12471

This study aimed to describe the early development of Clarias gariepinus, a species that has been introduced into various watersheds worldwide, in order to help the identification of its eggs, larvae and juveniles in natural environments. The material used was obtained via induced spawning during 1999. After spawning, the periodicity of sampling varied according to ontogenic development. We analyzed 12 eggs, 146 larvae and 6 juveniles. Newly fertilized eggs are spherical, with a double membrane, the density of which varies. Initially the larvae have little pigmentation but this intensifies during development. They have four pairs of well-developed barbels, an elongated body, long dorsal and anal fins, no adipose fin and vesicles surrounding the finfold and barbels. The sequence of formation of the fins is: caudal, dorsal, anal, pectoral and pelvic. Growth pattern analysis revealed that metamorphosis usually occurs during the flexion stage. The reproductive performance of the species and its rapid early development favor aquaculture; however, they may also favor its invasion of natural environments, representing a threat for native populations.

<b>Desenvolvimento inicial de <em>Hoplias</em> aff. <em>malabaricus</em> (Bloch, 1794) (Osteichthyes, Erythrinidae) da planície alagável do alto rio Paraná, Brasil</b> - DOI: 10.4025/actascibiolsci.v30i2.3608 <b>Early development of <em>Hoplias</em> aff. <em>malabaricus</em> (Bloch, 1794) (Osteichthyes, Erythrinidae) in the upper Paraná river floodplain, Brazil</b> - DOI: 10.4025/actascibiolsci.v30i3.3608

Este trabalho teve por objetivo caracterizar o desenvolvimento inicial de <em>Hoplias</em> aff. <em>malabaricus</em>. As amostragens foram realizadas entre novembro de 1991 e fevereiro de 1995, em 42 estações de coleta, distribuídas em vários ambientes da planície alagável do alto rio Paraná, Brasil. Para a obtenção do material, foram realizadas amostragens nas regiões pelágica (rede de plâncton) e litorânea (“peneirão”). Para a caracterização das diferentes fases, os indivíduos foram separados em períodos larval (estágios de pré-flexão, flexão e pós-flexão) e juvenil. Foram analisadas as variáveis morfométricas e merísticas em 269 larvas e 74 juvenis, com comprimento padrão variando entre 6,17 e 49,12 mm. As larvas apresentaram corpo fusiforme e altamente pigmentado, olhos grandes, intestino longo e boca terminal. O número total de miômeros variou de 37 a 45 (23 a 28 pré e 11 a 18 pós-anal). Os juvenis apresentaram a forma do corpo semelhante a do adulto. O número de raios das nadadeiras encontrado para a espécie foi: peitoral 12; pélvica 7-9; dorsal 13-15; e anal 10-12. A análise do crescimento indicou a metamorfose no início do desenvolvimento desta espécie.<br>The aim of this study was to characterize the early development of <em>Hoplias</em> aff. <em>malabaricus</em>. The sampling was conducted during the period from November 1991 through February 1995, at 42 stations distributed in different environments of the upper Paraná river floodplain, Brazil. The specimens were taken from limnetic and littoral regions. Specimens were separated according to their development in larval (preflexion, flexion and postflexion stages) and juvenile periods. Morphometric and meristic variables were analyzed in 269 larvae and 74 juveniles (standard length ranging from 6.17 mm to 49.12 mm). Larvae showed fusiform body and intense pigmentation, a long intestine, large eyes and terminal mouth. Number of myomeres ranged from 37 to 45 (23-28 pre and 11-18 post-anal). The juveniles presented a body shape similar to their adults. The numbers of fin rays were: pectoral, 12; pelvic, 7-9; dorsal, 13-15; and anal, 10-12. Analysis of the growth showed metamorphosis in the early development of this species

Fish larvae from the upper Paraná River: do abiotic factors affect larval density?

The purpose of this study was to evaluate the role of abiotic factors on fish larvae occurrence. Samplings were carried out monthly at 12 stations (grouped in four areas) in the Amambaí, Ivaí and Paraná rivers and in the Itaipu Reservoir (upper Paraná River basin), from October 1994 to January 1995 (spawning season). Simultaneously, we obtained water temperature, pH, electrical conductivity, dissolved oxygen, water level, water velocity, and rainfall. Principal Component Analyses (PCA) and Detrended Correspondence Analyses (DCA) were applied to summarize abiotic and larvae density data, respectively. Amambaí River differed significantly from the other areas in relation to abiotic factors. Itaipu Reservoir differed significantly from the other areas considering species composition, and the Ivaí River also differed from the Paraná River. The relationship among PCA and DCA axes were significant, indicating that abiotic factors do influence larva. For example: Leporinus elongatus prefered the Amambaí River, Hypophthalmus edentatus, Plagioscion squamosissimus, and Hoplias aff. malabaricus the Itaipu Reservoir, and Pimelodus maculatus, Auchenipterus osteomystax and Iheringichthys labrosus the Ivaí River. We suggest that species selected some abiotic factors characteristic to a given environment as spawning grounds

Early development of <em>Auchenipterus osteomystax</em> (Osteichthyes, Auchenipteridae) from the Paraná river basin, Brazil Caracterização do desenvolvimento inicial de <em>Auchenipterus osteomystax</em> (Osteichthyes, Auchenipteridae) da bacia do rio Paraná, Brasil

The aim of the present study was to characterize the early development of <em>Auchenipterus osteomystax</em> (Ribeiro, 1918) (Osteichthyes, Auchenipteridae). Specimens were taken from plankton samples in the Upper Paraná river, Ivaí river, Upper Ivinhema river and Itaipu Reservoir. Seventy-four larvae and seven juveniles (with standard length ranging from 5.25 mm to 39.0 mm) were analyzed. Specimens were identified and separated according to their development and morphometric and meristic analyses were performed. The early development of <em>A. osteomystax</em> follows the pattern of other Siluriformes. However, individuals presented more pigmentation on the head and on fore part of the body. Number of myomeres ranged from 44 to 50<br>O objetivo deste trabalho é caracterizar o desenvolvimento inicial de <em>Auchenipterus osteomystax</em> (Ribeiro, 1918) (Osteichthyes, Auchenipteridae). O material analisado é proveniente de amostras coletadas no plâncton no alto rio Paraná, rio Ivaí, alto rio Ivinhema e reservatório de Itaipu. Foram analisadas 74 larvas e 7 juvenis, entre 5,25 mm e 39 mm de comprimento padrão. Os espécimes foram identificados e separados em diferentes estágios, e foram obtidas as variáveis morfométricas e merísticas. As larvas de <em>A. osteomystax</em> apresentam o desenvolvimento inicial semelhante ao de outros Siluriformes, no entanto são caracterizadas principalmente por apresentar um aglomerado de pigmentos na cabeça e na região anterior do corpo e número de miômeros variando de 44 a 5