ABSTRACT
The present study investigates the δ13C and δ15N isotopic composition in frozen samples (control), samples in alcohol and in formaldehyde of Plagioscion squamosissimus and Hypophthalmus edentatus. 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 δ13C from the H. edentatus 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 species of freshwater fish.
O presente estudo investiga a composição isotópica de δ13C e δ15N entre as amostras congeladas (controle), em álcool e em formol de Plagioscion squamosissimus e Hypophthalmus edentatus. De cada indivíduo foi extraída uma faixa de músculo localizada na região acima da linha lateral, na base da nadadeira dorsal, a qual foi subdividida em três partes iguais, sendo cada uma delas submetida a um tipo de tratamento: congelamento - grupo control (-15oC), conservação em álcool 70% e fixação em formol 4%. As amostras foram mantidas nos referidos tratamentos por 30 dias, enxaguadas e submersas em água destilada por 4h. Em seguida, foram secas em estufa de ventilação a 60oC por 48h e maceradas até a obtenção de pó. Identificou-se diferença significativa nos valores isotópicos de carbono e de nitrogênio, entre o controle e as amostras de álcool e as de formol, com exceção do δ13C das amostras mantidas em formol de H. edentatus. Constatou-se que os valores isotópicos de carbono das amostras conservadas em álcool foram, na sua maioria, enriquecidos quando comparados com as controle, ao passo que, as amostras em formol tiveram os valores deplecionados em relação ao controle. Os valores isotópicos de nitrogênio, tanto para as amostras conservadas em álcool, quanto em formol, foram enriquecidos quando comparados aos valores daquelas congeladas, sendo estes independentes dos conservantes utilizados. Assim, a correção isotópica deve ser realizada de acordo com o isótopo e o conservante empregado para espécies de peixe de água doce.
Subject(s)
Animals , Fishes , Food Preservatives , IsotopesABSTRACT
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 aim of this work was to investigate differences in the energy content during reproductive cycle of two species of fish with different life strategies: Brycon hilarii (k-strategist) and Hypophthalmus edentatus (r-strategist). Fifty-four samples of B. hilarii and 82 of H. edentatus monthly collected from October, 2000 to March, 2004, in Manso reservoir and its influence area were selected. The caloric content was determined for each individual, in kcal g-1 of dry weight, through bomb calorimetry (Parr 1261). Comparisons among the obtained caloric values, the condition factor (K) and the Gonado Somatic Relation were reported. It was observed that, in general, the average values of the K and of the caloric content were higher among males than among females of both species. Significant differences were found in the comparisons accomplished between the energy content and the condition factor on individuals of both species. While B. hilarii presents the highest concentrations of energy in the muscles, during the maximum gonadal development, H. edentatus showed these values in the beginning of gonadal maturation. B. hilarii and H. edentatus, with different life strategies, build up and mobilize energy in different ways during reproductive cycle.
Com o objetivo de investigar diferenças no conteúdo de energia durante o ciclo reprodutivo, foram selecionados 54 exemplares de Brycon hilarii (k-estrategista) e 82 de Hypophthalmus edentatus (r-estrategista) em amostragens realizadas mensalmente, entre outubro de 2000 e março de 2004, no reservatório de Manso, Estado do Mato Grosso do Norte e em sua área de influência. Determinou-se, para cada indivíduo, o conteúdo calórico, em kcal g-1 de peso seco, com auxílio da bomba calorimétrica (Parr 1261) e, realizaram-se comparações entre os valores calóricos obtidos, o fator de condição (K) e a relação gonadossomática. Observou-se que, em geral, os valores médios de K e do conteúdo calórico foram superiores nos machos das duas espécies analisadas, embora não tenham sido identificadas diferenças significativas entre os sexos. Constatou-se que os valores calóricos de H. edentatus foram superiores aos de B. hilarii, enquanto os valores do fator de condição foram contrários, apresentando-se superiores para B. hilarii. Diferenças significativas foram constatadas nas comparações realizadas entre o conteúdo energético e o fator de condição, de indivíduos de ambas as espécies. Enquanto B. hilarii apresentou as mais elevadas concentrações de energia nos músculos, durante o máximo desenvolvimento gonadal, em H. edentatus, isso ocorreuquando iniciava o processo de maturação gonad