ABSTRACT
The present study investigates the 13C and 15N isotopic composition in frozen samples (control), samples in alcohol and in formaldehyde of Plagioscion squamosissimus and Hypophthalmus edentates. From each individual we extracted a strip of muscle from the region above the lateral line, in the dorsal fin base, that was divided into three equal parts, each one was submitted to one type of treatment: freeze control group (-15oC), conservation in alcohol 70% and fixation in formaldehyde 4%. Samples were kept under those treatments for 30 days, washed and submerged in distilled water for 4 hours. Afterwards, they were dried up in air oven at 60oC for 48 hours and macerated until the obtaining of a fine powder. A significant difference was found in isotopic values of carbon and nitrogen, between the control and the samples in alcohol and formaldehyde, except for 13C from the H. edentates samples in formaldehyde. The carbon isotopic values of samples in alcohol were mostly enriched compared to control, whereas the samples in formaldehyde presented depleted values in relation to the control. The nitrogen isotopic values for both samples preserved in alcohol and formaldehyde were enriched when compared to the values of frozen samples, independently of used preservatives. Therefore, the isotopic correction should be accomplished according to the isotope and preservative employed for
The present study investigates the 13C and 15N isotopic composition in frozen samples (control), samples in alcohol and in formaldehyde of Plagioscion squamosissimus and Hypophthalmus edentates. From each individual we extracted a strip of muscle from the region above the lateral line, in the dorsal fin base, that was divided into three equal parts, each one was submitted to one type of treatment: freeze control group (-15oC), conservation in alcohol 70% and fixation in formaldehyde 4%. Samples were kept under those treatments for 30 days, washed and submerged in distilled water for 4 hours. Afterwards, they were dried up in air oven at 60oC for 48 hours and macerated until the obtaining of a fine powder. A significant difference was found in isotopic values of carbon and nitrogen, between the control and the samples in alcohol and formaldehyde, except for 13C from the H. edentates samples in formaldehyde. The carbon isotopic values of samples in alcohol were mostly enriched compared to control, whereas the samples in formaldehyde presented depleted values in relation to the control. The nitrogen isotopic values for both samples preserved in alcohol and formaldehyde were enriched when compared to the values of frozen samples, independently of used preservatives. Therefore, the isotopic correction should be accomplished according to the isotope and preservative employed for
ABSTRACT
The stable isotopes have been used to obtain the turnover rate in aquatic animals. This is one more tool to help making decisions about the conservation, considering that the anthropic impacts threaten specific areas of food, reproduction and growth of the species in natural ambient. On the other hand, in the aquaculture, the knowledge about the conversion speed of the food in tissue helps to better estimate the production. Based on that, the aim of this paper is to make a revision about the studies carried out related to the turnover rate using stable isotopes, in ecology. The turnover consists of the new tissue synthesis and of the old tissue replacement using the animal composition present diet. The turnover rate depends on the animal tissue analyzed, on the development phase, on the time and on the abiotic parameters
Os isótopos estáveis vêm sendo utilizados na obtenção da taxa de turnover em animais aquáticos e representam mais uma ferramenta no auxílio à tomada de medidas de conservação, considerando que os impactos antrópicos ameaçam áreas específicas de alimentação, reprodução e crescimento de espécies em ambientes naturais. Na aqüicultura, por outro lado, o conhecimento da velocidade de conversão do alimento em tecido auxilia em melhores estimativas de produção. Neste sentido, o presente estudo pretende fazer uma síntese dos trabalhos realizados acerca das taxas de turnover em ecologia, com uso da técnica de isótopos estáveis. O turnover consiste na síntese do novo tecido e na substituição dos tecidos velhos utilizando a composição da dieta atual do animal. A taxa de turnover é dependente do tecido animal analisado, da fase de desenvolvimento, do tempo e dos parâmetros abióticos