Energy budget and physiology in early ontogenetic stages of the Amazon river prawn☆

An energy budget allows an understanding about the way in which the energy ingested is distributed among the various functions. In this study, the energy ingested by Zoeae, Decapodids and Juveniles of M. amazonicum allocated to growth, metabolism, nitrogen excretion, feces, and exuviae was measured. Also the main organic substrates oxydized were determined. Feces produced was estimated by the difference between the energy ingested and the energy assimilated plus excreted. Metabolism was assessed based on the oxygen consumption. Ammonia excretion was measured using a spectrophotometer. The oxygen consumed/nitrogen excreted ratio was determined to obtain the substrate oxidized. The energy of the organisms, food and exuviae was determined by wet combustion. Ingestion, body energy content and energy channeled into metabolism and excretion increased during ontogeny and differed between some stages. About 4% of the ingested energy was lost as exuviae. Zoea II showed low assimilation, and ∼46 % of the energy ingested was lost as feces. In Zoea III the accumulation of energy in the biomass predominates (∼45 %) but in Decapodids II and III the use of energy to maintain metabolism predominates (∼88 %). Proteins were the main substrate oxidized. Except in Zoea III, the energy used for metabolism varied from twice to twelve times the energy channeled to growth. This differential may be associated with an uneven pattern in the use of nutrients, growth and behavior. Zoea VI to Decapodid 3 showed a higher relationship in respiration /growth, which may indicate that Artemia nauplii are not suitable for feeding in these stages. The energy budget showed that most energy is channeled to feces (Zoea II) or to metabolism in the early stages. Therefore, the efficiency is low and there is a great potential to channel energy lost in metabolic processes to accumulate in biomass and accelerate larval development by changes in management.