<b>Influence of <i>Eichhornia crassipes</i> and Lemna sp. on the natural diet of <i>Astyanax altiparanae</i> Garutti & Britski, 2000 in the initial stages

Abstract

ABSTRACT. Aiming to study the changes in the diet of Astyanax altiparanae in the early developmental stages, in the presence of Eichhornia crassipes (EC) and Lemna sp. (LM), larvae of Astyanax altiparanae were stocked in eight tanks of 900 L (500 ind. tank -1 ), four with EC and four with LM covering 50% surface. Tanks were inoculated with plankton and received 3.0 g inorganic fertilizer (NPK-7:14:8) and 1.5 g every week. At every three days, three larvae were taken from each tank, fixed in 4% formaldehyde and grouped into four age classes (I: 6 to 12 days, II:15 to 21 days, III:24 to 30 days; IV:33 to 39 days). The analysis of dominance and frequency of occurrence (FO) of food items indicated that, at this stage, A. altiparanae is generalist. In class I, there was a greater dominance and FO of Lecane bulla and Alona sp. in digestive tracts in the presence of both EC and LM, respectively; and larvae started to consume larger organisms, such as Chironomidae, in other age classes with EC. In the presence of LM, Alona sp. was dominant in class II; Chironomidae, in class III and Centropyxis sp., in class IV. Diatoms have greater FO both in EC and in LM. In class III, with EC, Chironomidae had higher FO, as well as Arcella sp. and Scenedesmus spp. with LM. The highest FO in class IV was found for L. bulla and Scenedesmus spp., with EC and LM, respectively. It can be concluded that EC and LM influenced the diet of Astyanax altiparanae, with alterations according to the availability of organisms and increase in age.Keywords: fish larvae, floating macrophyte, plankton, larval development, diet. ), sendo quatro com EC e quatro com LM cobrindo 50% da superfície destes. Os tanques foram inoculados com plâncton e receberam 3,0 g de fertilizante inorgânico (NPK-7:14:8) e 1,5 g semanalmente. A cada três dias foram coletadas três larvas de cada tanque, fixadas em formol a 4% e agrupadas em quatro classes de idade (I: 6 a 12 dias, II: 15 a 21 dias, III: 24 a 30 dias e IV:33 a 39 dias). Relacionando a dominância e frequência de ocorrência (FO) dos itens alimentares verificou-se que, nesta fase, o A. altiparanae é generalista. Na classe I, houve maior dominância e FO de Lecane bulla e de Alona sp. nos tratos digestórios na presença de EC e LM, respectivamente, passando a consumir organismos maiores como Chironomidae nas demais classes com EC. Na presença de LM, Alona sp. foi dominante na classe II, Chironomidae na III e Centropyxis sp. na IV. As diatomáceas tiveram maior FO tanto em EC quanto em LM. Na classe III, com EC Chironomidae teve maior FO, assim como Arcella sp. e Scenedesmus spp. com LM. A maior FO na classe IV foi de L. bulla e Scenedesmus spp. com EC e LM, respectivamente. Concluiu-se que EC e LM influenciaram a dieta de A. altiparanae, alterando-a de acordo com a disponibilidade dos organismos e com o aumento da idade. Influência dePalavras-chave: larva de peixe, macrófita flutuante, plâncton, desenvolvimento larval, alimentação.

<b>Diet of fish (Characiformes: Characidae) during early developmental stages in the Upper Paraná river basin, Brazil

“…In the second and third classes (14 to 20 and 23 to 29 days of life), there were changes with increase in the frequency of occurrence of algae, mainly with the young stages of A. lacustris, M. obtusidens and P. lineatus; and for P. mesopotamicus, there were higher values for cladocerans. Furuya, Hayashi, Furuya, and Sakaguti (2002), on Pseudoplatystoma corruscans, Borges et al (2006) and Suiberto et al (2009), on species of the genus Bryconamericus, observed an increase in the frequency of occurrence of larger items (copepods, ostracods and insect larvae) and reduction in the occurrence of smaller items (rotifers), according to increasing age of the post-larvae, which was also observed by Galdioli, Hayashi, Soares, and Marques (2017) for Astyanax lacustris at early developmental stages.…”

“…Similar results were obtained by Sipaúba-Tavares (1993), with larvae of C. macropomum and hybrids of C. macropomum x P. mesopotamicus, which prefer smaller organisms, mainly rotifers at the beginning of development, starting to consume larger organisms (cladocerans and copepods) as they grow. In studies with A. lacustris, Galdioli et al (2017), there were changes in the diet of these fish as they develop, with preference for Lecane sp. during the first days of development.…”