Post-larval Colossoma macropomum (Characiformes, Serrasalmidae) show better performance in excavated than concrete tanks under different feeding strategies

As the global human population increases, the demand for food grows and, consequently, practices such as aquaculture have become more common. Colossoma macropomum (Cuvier, 1818) is a native Amazonian species, considered to be the second most cultivated fish in the country. We compared the development of post-larval C. macropomum of different ages, submitted to combinations of food management on a commercial production scale. Two experiments tested the delivery of i) 55% crude protein feeding, ii) natural feeding by fertilizing the water and iii) a combination of both during hatchery in concrete tanks (10 m 2) or excavated soil-bottom tanks (4502) subjected to distinct fertilization protocols and storage densities. The weight and length of the post-larvae grown in ponds were greater (p < 2.0x10-16) for the mixed treatment, except during the first week of larvae, in which values were similar (p & 8804; 1.76x10-14) to the fertilization treatment. Concrete tanks with fertilization management without feeding were similar to the mixed treatment (p & 8804; 1.38x10-7); however, during the first week of external larvae production, the growth performance under fertilization treatment was superior to the others. Food management in excavated tanks, when compared to the same management performed in concrete tanks, registered higher averages for the productive variables of C. macropomum cultivated at the density of 200 post-larvae m-2 in all evaluated food strategies. It was verified that post-larvae of C. macropomum did not develop well in the first weeks of life when receiving only formulated diets. The increase in natural food availability through fertilization positively influenced the performance of the species, which can remain without feeding until the second week of life.

Occurrence of Arcellidae (Amorphea, Arcellinida) in a coastal stream in the State of Rio de Janeiro

The aim of this study was to elaborate a taxonomic survey on the testate amoebae of the Family Arcellidaein coastal streams in the State of Rio de Janeiro. Six samplingswere conducted in Ubatiba coastal stream (Maricá, RJ). In total, 130 liters water were filtered through a conical net of 60-μm mesh and preserved in 4% formalin. Organisms were identified with the aid of an inverted trinocular microscope. The morphological characteristics (lobose testate amoebae with shell composed of granular chitinoid elements) of each species were recorded. The species were described and illustrated. For the verification of new taxa records of Arcellidae in Rio de Janeiro and their distribution in Brazil, a search based on indexarticles by Scopus, Web of Science and Google Scholar using the keywords "tecamebas", "testate amoebae", "Arcella", "Arcellidae", "Brazil" and "Rio de Janeiro", was performed. Eight Arcellidaespecies were recorded. Some ecological and taxonomic information was provided. Due to the small amount of information on testate amoebae, this study is important because it reduces the knowledge gap regarding this community in the State of Rio de Janeiro. Furthermore, we suggest new studies on species identification to be conducted to expand regional knowledge about these organisms.

Rotifer community structure along a stretch under the influence of dams in the Upper Paraná River floodplain / Estrutura da comunidade de rotíferos ao longo de um trecho sob a influência de barragens na planície de inundação do alto rio Paraná

The construction of reservoirs imposes substantial impact on freshwater ecosystems and changes the ecological aspects of the lotic system downstream of dams. We hypothesized an increasing dissimilarity between communities in the sampling sites according to increasing distance from the Porto Primavera Dam. In addition, we expect that the rotifer community in the last sampling site will be influenced more by environmental variables related to trophic status. Samplings were conducted under the water surface of ten sites on the Paraná River in August 2013. Environmental variables were also determined. The highest number of taxa belonged to families Brachionidae, Lecanidae and Trichocercidae. The most abundant species was observed to Synchaeta oblonga, Keratella cochlearis, Brachionus calyciflorus. The species dissimilarity between sampling sites, tested using the Sorensen index, showed high dissimilarity between sampling sites. Redundancy analysis indicated a significant relationship between environmental variables (total phosphorus and ammonia) and abundance of Brachionus calyciflorus and Keratella cochlearis, in the last sampling site. Our results suggest a greater dissimilarity between the rotifer communities according to increasing distance from the Porto Primavera Dam. In addition, a higher influence of the environmental variables related to trophic conditions was observed in the last sampling site, and influenced indirectly the occurrence and abundance of some rotifer species, due to increased availability of food resources, confirming the predicted hypothesis.

A construção de reservatórios impõe considerável impacto sobre os ecossistemas de água doce e altera os aspectos ecológicos do sistema lótico a jusante das barragens. A hipótese foi que ocorrerá maior dissimilaridade entre as comunidades nos pontos amostrados à medida que se afastam da barragem de Porto Primavera. Espera-se, ainda, que a comunidade de rotíferos do último ponto de amostragem seja mais influenciada pelas variáveis ambientais relacionadas à trofia. As amostragens foram realizadas à subsuperfície da região pelágica em dez pontos no rio Paraná no mês de agosto de 2013. As espécies mais abundantes foram Synchaeta oblonga, Keratella cochlearis, Brachionus calyciflorus. As variáveis ambientais também foram determinadas. O maior número de táxons registrados pertenceu às famílias Brachionidae, Lecanidae e Trichocercidae. A similaridade da composição de espécies calculada de acordo com o índice de Sorensen registrou elevada dissimilaridade entre os pontos amostrados. A análise de redundância constatou a relação significativa entre as variáveis ambientais (fósforo total e amônia) e a abundância de Brachionus calyciflorus e Keratella cochlearis, no último ponto de amostragem. Nossos resultados sugerem que ocorreu maior dissimilaridade entre as comunidades de rotíferos à medida que se afastam da barragem de Porto Primavera. Além disso, foi observada maior influência das variáveis ambientais relacionadas às condições tróficas no último ponto de amostragem, e influenciou indiretamente a ocorrência e abundância das espécies de rotíferos, por causa do aumento da disponibilidade de recursos alimentares, corroborando com a hipótese predita.