História de vida de Laetacara aff. araguaiae Ottoni & Costa, 2009 (Perciformes, Cichlidae) em dois riachos no Noroeste do Estado de São Paulo, Brasil
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2010-06-01
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Instituto Virtual da Biodiversidade (BIOTA/FAPESP)
Resumo
Foi investigada a estrutura em tamanho, densidade, alimentação, fecundidade e presença de ectoparasitos em duas populações de Laetacara aff. araguaiae no Noroeste do Estado de São Paulo, em dois riachos, sendo um estruturalmente mais heterogêneo (HET) e outro relativamente mais simplificado (SIM). Foram realizadas seis amostragens em cada riacho, sendo três no período chuvoso (outubro, dezembro/2007, fevereiro/2008) e três no seco (abril, julho e setembro/2008), durante 15 minutos de coletas em cada riacho, utilizando-se uma peneira com malha de 3 mm. Foram coletados 118 indivíduos no riacho HET (49 no período chuvoso e 69 no seco) e 146 no riacho SIM (82 no chuvoso e 64 no seco). Os peixes coletados no riacho HET foram maiores do que aqueles coletados no riacho SIM, independente do período considerado. A densidade populacional foi similar entre os dois riachos, com aumento que coincidiu com o pico do período seco. Fragmentos de insetos aquáticos representaram os itens mais importantes da dieta, com variação espaço-temporal pouco relevante. A fecundidade foi significativamente maior no riacho HET, variando de 977 a 1.602 ovócitos, em contraste com as fêmeas do riacho SIM, que apresentaram de 338 a 814 ovócitos. Os ectoparasitos (Digenea) estiveram presentes somente em indivíduos do riacho SIM e encontravam-se aderidos às nadadeiras (dorsal e anal), com maior prevalência no mês de outubro. A alimentação e densidade foram similares nas duas populações de Laetacara aff. araguaiae, ao contrário da estrutura em tamanho e fecundidade. As diferenças nestes parâmetros demográficos não ocorrem ao acaso e são possivelmente reflexo das elevadas taxas de parasitismo no riacho mais simplificado que determinam menor alocação de recursos para crescimento e reprodução nesta população de peixes.
The structure in size, density, feeding, fecundity, and presence of ectoparasites in two populations of Laetacara aff. araguaiae was investigated in two streams, in Northwestern São Paulo State, one structurally more heterogeneous (HET) and other relatively more simplified (SIM). Six samples were taken in each stream, three in the wet period (October, December/2007, February/2008) and three in the dry period (April, July, September/2008), which were performed during 15 minutes of sampling in each stream, using a 3 mm-mesh sieve. A total of 118 individuals in HET stream (49 in the wet season and 69 in dry) and 146 in SIM stream were captured (82 in wet and 64 in dry). Fish collected in HET stream were larger than those collected in the SIM, both in wet and dry periods. The density was similar between two streams, with an increase agreeing with the peak of the dry period. Fragments of aquatic insects were the most important items of diet, which showed little spatial and temporal variation. Fecundity was significantly higher in HET, ranging from 977 to 1,602 oocytes, in contrast with females of the SIM, which had 338 to 814 oocytes. The ectoparasites (Digenea) were present only in specimens of the SIM, and were attached to the fins (dorsal and anal) with higher prevalence in October. Feeding and density were similar in the two populations of Laetacara aff. araguaiae, contrasting with the structure in size and fecundity. The differences in these demographic parameters do not occur randomly and are possibly reflecting the high rates of parasitism in the more simplified stretch that determines lower resources allocation to growth and reproduction of fishes in this population.
The structure in size, density, feeding, fecundity, and presence of ectoparasites in two populations of Laetacara aff. araguaiae was investigated in two streams, in Northwestern São Paulo State, one structurally more heterogeneous (HET) and other relatively more simplified (SIM). Six samples were taken in each stream, three in the wet period (October, December/2007, February/2008) and three in the dry period (April, July, September/2008), which were performed during 15 minutes of sampling in each stream, using a 3 mm-mesh sieve. A total of 118 individuals in HET stream (49 in the wet season and 69 in dry) and 146 in SIM stream were captured (82 in wet and 64 in dry). Fish collected in HET stream were larger than those collected in the SIM, both in wet and dry periods. The density was similar between two streams, with an increase agreeing with the peak of the dry period. Fragments of aquatic insects were the most important items of diet, which showed little spatial and temporal variation. Fecundity was significantly higher in HET, ranging from 977 to 1,602 oocytes, in contrast with females of the SIM, which had 338 to 814 oocytes. The ectoparasites (Digenea) were present only in specimens of the SIM, and were attached to the fins (dorsal and anal) with higher prevalence in October. Feeding and density were similar in the two populations of Laetacara aff. araguaiae, contrasting with the structure in size and fecundity. The differences in these demographic parameters do not occur randomly and are possibly reflecting the high rates of parasitism in the more simplified stretch that determines lower resources allocation to growth and reproduction of fishes in this population.
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Palavras-chave
structure in size, Density, Feeding, fecundity, ectoparasites, Heterogeneity, Upper Paraná, estrutura em tamanho, densidade, alimentação, fecundidade, ectoparasitos, heterogeneidade, Alto Paraná
Como citar
Biota Neotropica. Instituto Virtual da Biodiversidade | BIOTA - FAPESP, v. 10, n. 2, p. 153-158, 2010.