The present study was designed to test the effects of type of binder on growth, nutritional physiology, total apparent digestibility, and some elements of the energetic balance of early O. maya juveniles. Two experiments were performed. One was aimed at evaluating the effect of type of binder on growth, nutritional physiology, and energetic balance and the other at knowing the effect of the binder on total apparent digestibility of O. maya. Binder type affected growth and survival of early O. maya juveniles. Octopuses fed alginate-bound crab meat lost weight and died, revealing that this type of binder limits nutrient absorption from the diet. In contrast, when gelatin was used as binder, energetic balance was similar to that obtained in animals fed natural crab, indicating that octopuses can digest gelatin. Apparently, gelatin promotes absorption of nutrients similar to that observed when octopuses were fed pieces of fresh crab. Salivary glands produce enzymes that are used to predigest the food. Results of the present study indicate that octopuses require higher enzyme activity to digest fresh crab than when animals are fed gelatin-bound crab paste, and that intracellular digestion in the digestive gland is similar in animals fed either type of diet. The present study reports, for the first time, differences among binders used for cephalopods' diet. Although no compounded feed formulations are available for cephalopods, it is a necessary step in the search for an adequate compounded feed for this novel species in aquaculture.

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Proteinases from hepatopancreas (HP) and gastric juice (GJ) from wild and cultured red octopus (Octopus maya) were characterized. Hepatopancreas assays revealed optimal activity at pH 4, 9-10 and 10 for wild and pH 3, 8, and 9, for cultured octopuses, for total proteinases, trypsin and chymotrypsin, respectively. In the gastric juice, maximum activity was recorded at pH 6, 8, and 7 for total proteinases, trypsin, and chymotrypsin, respectively for both wild and cultured octopus. A reduction on enzyme activity of 70 and 20% was observed in HP and GJ extracts, respectively when protease inhibitor Pepstatin A was used. That result suggests that the main proteases in the HP were aspartic acid proteinases type (possibly Cathepsin D) and some of them were present in the GJ. Dissociating discontinuous polyacrylamide gel electrophoresis showed activity bands between 20 and 28, 30 and 34, 35 and 45, 60 and 70 kDa, and a last one between 75 and 100 kDa. We concluded that extracellular digestion of O. maya takes place in an acid environment, around pH 6. In contrast, intracellular digestion in the HP is developed at pHs between 3 and 4, where cathepsin D could be the most important enzyme for O. maya.

A study was conducted using a bioenergetics approach to generate information on energy requirement and feed utilization of Litopenaeus stylirostris. Animals (initial mean weight 21 ± 1 g were fed ad libitum six experimental diets, ranging from 25 to 58% crude protein (CP), for 50 days.Weight gain increased from 21 to 30 g with increasing dietary protein level. Survival rates averaged 80%. Basal metabolism (HeE) and heat increment of feeding (HiE) were monitored using respirometry. HeE was on average 1 kJ shrimp − 1 day − 1 or 47 kJ kg live weight − 1 day (22 kJ/kg 0.8 . d − 1 ), slightly more than what is observed in fish. HiE averaged 0.2 kJ/shrimp − 1 day − 1 or 10 kJ kg live weight − 1 day − 1 (4 kJ/kg 0.8 d − 1 ). It represented 31% and 12% digestible energy intake (DEI) for shrimp fed on 58% CP and 25% CP diet respectively. Non-fecal (UE + ZE) energy calculated on the basis of N-ammonia excretion averaged 0.2 μg N-ammonia/g dry wt./mn or 25 J live shrimp − 1 day − 1 in fasting stage and increased to 40 J in post-prandial stage. Ammonia production increased with increasing dietary crude protein (CP). The O:N ratio indicated that protein was increasingly used as an energy substrate as CP increased. The information was used to construct an energy budget for shrimp fed a protypical 40% CP diet. Gross energy intake (IE) was estimated at 6.5 kJ live shrimp − 1 day − 1 ; digestible energy intake (DEI) at 5, urinary and branchial excretion (UE + ZE) at 1.2, total heat production (HE) at 3.2; recovered energy (RE) at 0.6 (or 11% DEI). L. stylirostris adults issued from domesticated strain appeared to be more efficiently utilizing (i.e. converting into carcass energy) protein than carbohydrates. This preliminary energy budget can be used to construct theoretical feed requirement and waste outputs model for L. stylirostris.