Moina micrura Kurtz 1874, (Crustacea: Anomopoda): Alternativa de alimento vivo para larvicultura de peixes amazônicos

Abstract

As far as we know about live feeds production, it has always been the most limitation factor to large-scale zooplankton cultivation in aquaculture practices. The sites designated for the zooplankton production are usually tanks that are fertilized with organic or inorganic nutrients to provide the development of microalgae to feed and support the growth of zooplankton. Microalgae composition and density has been reported to be one of the main controlling factors for zooplankton’s population growth during cultivation, knowing that the low availability of this resource decreases the number of produced progenies and can even change the cladocera’s reproduction type, from asexual reproduction to sexual, where the females produce at most two progenies, that go into dormancy. Resting eggs production leads to several implications involving both the production of zooplankton itself and zooplankton as a living food for the success of larviculture stage. That way, understanding the role of these forms for the zooplankton’s production as a live feed, besides of perceiving under what conditions the zooplankton produces dormant forms, was the purpose of this study. To understand this role of resting eggs in the cultivation process, a tank (9.6x4.8x0.9m) of INPA was used. In the tank, sampling was done and used to estimate density of phytoplankton, sediment sampling for both density estimation and daily hatching of resting eggs, as well as the collection of resting eggs produced by the active community in the tank. In order to understand under what conditions zooplankton starts producing this eggs, the effect of different densities of phytoplankton were tested (A1 5x103, A2 5x104, A3 5x106 cells / mL) and also different densities of zooplankton (initial density C1 5, C2 15 and C3 30 organisms), in the production of resistance forms in Moina micrura. The estimated density was 1.18 effipios/g in sediment. The mean hatching rate was 20.8 individuals m-2 day-1. The production’s average rate was 164.5 resting eggs m-2 day-1. The resting eggs present in the sediments are determinant for the success in zooplankton production. The density of phytoplankton was preponderant for asexual reproduction prevailing in the population during the period of study. We didn’t find relation between the increase in population density and the production of resting eggs in this study.