ALBERT

Notes: The influence of protein and energy levels on growth rate, survival, pre- and post-prandial oxygen consumption, ammonia excretion, haemolymph glucose (HG), glycogen in digestive gland and osmotic pressure (OP) in white shrimp Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles was studied. Diets containing a high-quality protein at a protein/energy (P/E) ratio of 16, 26, 31 and 36 mg kJ−1 were fed at 20% of shrimp body weight of two sizes: 〈 1 g and 〉 1 g. Both species showed a optimum P/E ratio of 36 mg kJ−1 (33–44% protein and 6–23% carbohydrate) in juveniles 〈 1 g. For shrimp 〉 1 g, L. setiferus showed a higher growth rate in the diet with 16 mg kJ−1 (27% protein; 32% carbohydrate) and L. vannamei between 26 and 36 mg kJ−1 (33–44% protein and 6–23% carbohydrate). In both experiments, the growth rate of L. vannamei was 2–3 times that observed in L. setiferus. Routine oxygen consumption and apparent heat increment (AHI) of L. setiferus juveniles was two times higher than that observed in L. vannamei juveniles, which could indicate that L. setiferus has a higher metabolic rate. The O/N ratio varied according to protein level, with higher values (O/N = 180) with a 16-mg kJ−1 diet and lower values (O/N = 73) with a 36-mg kJ−1 diet in L. setiferus juveniles. A similar variation in O/N ratio was obtained in L. vannamei fed with all diets with an interval between 22 and 50. An inverse relation between ammonia excretion and HG, and digestive gland glycogen (DGG) in relation to an increase in the P/E ratio indicate that both shrimp species are well adapted to use carbohydrates and/or proteins from their diet. The higher values of hyper-osmotic capacity (hyper-OC) were observed in L. setiferus 〈 1 g fed with 36 mg kJ−1 and the lowest in L. vannamei 〈 1 g fed with 31 mg kJ−1. Intermediate values of hyper-OC were observed in both species fed all diets indicating that osmotic factors of juveniles 〈 1 g of both species are more affected by the P/E ratio than juveniles 〉 1 g. All results showed that juveniles 〉 1 g of both species are less dependent of P/E ratio than juveniles 〈 1 g. Litopenaeus vannamei is a most tolerant shrimp species with a high capacity to use a wide range of dietary P/E ratios for growth, which may be due to its lower energy requirements. Litopenaeus setiferus showed a lower capacity to accept different P/E ratios but the optimum P/E ratio obtained with this species shows that L. setiferus accept diets with a high carbohydrate level as well. These results demonstrate that there are nutritional and physiological differences that explain the differences that have been observed when both species were cultured in commercial ponds.

Notes: An experiment was conducted to study the effect of protein level on the growth rate, survival, pre- and postprandial oxygen consumption, and ammonia (N-NH3) excretion in white shrimp. Penaeus setiferus (L.), juveniles. Diets containing 10%, 20%, 30%, 40% and 50% protein were provided at a proportion of 15% of the dry weight of shrimp weighing 0.19 ± 0.01g. The instantaneous growth rate was recorded for 45 days. The optimum protein level, in terms of the best growth rate, was that of the 30% protein diet (1.1 5g45days−1). All shrimp fed with the diets had significantly higher respiration rates after feeding because of the apparent heat increment (AHI). A greater postprandial nitrogen excretion (PPNE) excretion was also observed after feeding. Shrimp maintained on the 30% protein diet had the lowest AHI and PPNE coefficients (percentage of ingested energyl. and took the least time to reach the oxygen consumption and nitrogen excretion peak. The 0:N ratios varied according to protein level, with higher values (32 and 44, fasting and Feeding, respectively) with a 30% protein diet, and lower values (10 and 13. fasting and feeding, respectively) with 10% and 50% protein diets. These results indicate that P. setiferus juveniles use protein when fed with high (50%) and low (10%) protein diets, and lipid-protein substrates with a 30% protein diet. Under these conditions, P. setiferus grow better with a 30% protein diet where shrimp use food more efficiently.

Notes: Genetic differentiation and variability data of two populations of two species of shrimp (Litopenaeus setiferus (L.) and L. schmitti (Burkenroad)) have been obtained by electrophoretic analysis and by analysis of 16S mitochondrial DNA. Using eight polymorphic enzymes, the genetic distance (GD) between the two species was 0.165. The GD between L. setiferus populations was 0.0057 and between L. schmitti populations it was 0.0034. The greatest differentiation was found within, rather than between, populations, although the differentiation value between Mexican and Cuban populations varied in accordance with the geographic distance and ecological characteristic of each. We found a high similarity between these two species with a bimodal distribution of the loci with respect to genetic identity. The homology percentages for gene 16S fragments were compared with those from six different shrimp species (L. vannamei, L. stylirostris, Farfantepenaeus notialis, Metapeneopsis lamellata) and Artemia salina. Ninety-seven percent of identity was found by analysis of a 409 bp of 16S mitochondrial DNA. With these values a phylogenetic tree was made using parsimony criteria. The GDs obtained with this method confirm the classification proposed by Pérez-Farfante & Kensley (1997).

Notes: Growth rate, soluble-protein content and digestive-enzyme activities were studied in Litopenaeus vannamei (Boone, 1931) early post-larvae under six feeding regimens, which included combinations of freshly hatched Artemia nauplii, an artificial diet and algae. Growth (0.11 mg DW day−1) and soluble-protein content (61.8 μg protein larvae−1 at PL10) of post-larvae fed mixed diets were significantly higher (P 〈 0.05). An artificial diet used alone or co-fed with algae caused the lowest growth (0.03–0.05 mg DW day−1) and soluble-protein content (13.7–15.5 μg protein larvae−1 at PL10). Trypsin-like activity was higher (up to 10 times) in post-larvae fed Artemia nauplii and an artificial diet alone or plus algae. The artificial diet stimulated chymotrypsin activity, apparently in response to squid meal present in this diet. Amylase activity increased when post-larvae were fed the artificial diet. This was apparently related more to the origin of the starch than to the total carbohydrate level of the diet. No obvious relationship was found between enzyme activity and growth in any feed combination. Based on growth and soluble-protein content, we determined that partial substitution (50%) of Artemia nauplii by artificial diet and the use of algae co-fed beyond the first post-larval stage benefits growth and the nutritional state of L. vannamei post-larvae.

Notes: The effects of the density and type of food on oxygen consumption and ingestion rate of larvae of the white shrimp Penaeus setiferus fed diatoms Chaetoceros ceratosporum, flagellates Tetraselmis chuii and Artemia franciscana nauplii were analysed. Diatoms, flagellates and Artemia nauplii were fed at five densities from 10 to 5 × 103 cells mL−1, 0 to 4 × 103 cells mL−1, and 0.1, 0.5, 1.0, 1.5 and 2 nauplii mL−1, respectively. In three experiments, two of three types of food were maintained constant at concentrations of 30-40 × 103 cells mL−1 (diatoms), 2 × 103 cells mL−1 (flagellates) and 1 Artemia nauplii mL−1. The oxygen consumption in three experiments increased with larval stage, reaching maximum values in Mill except at lower feed concentrations. A maximum ingestion peak in MI was recorded in larvae fed diatoms, whereas that peak was observed in Mil in larvae fed flagellates. The maximum ingestion rate of Artemia nauplii was observed in Mill. Feed concentrations that produced an optimum metabolic rate as a consequence of equilibrium between ingested food and larval stages were obtained with 20 and 30 × 103 cells mL−1 of C. ceratosporum, 2 and 3 × 103 cells mL−1 of T. chuii, and 1.0 Artemia nauplii mL−1. These concentrations would be the most suitable for producing P. setiferus postlarvae.

Notes: An artificial diet for shrimp larvae was microencapsulated with a polysaccharide blend [66% gum arabic, 17% mesquite gum and 17% maltodextrin 10 dextrose equivalent (DE)]. Microencapsulated diet (MD) was fed to mysis alone, as a co-feed with the microalgae Chaetoceros cerastosporum and Tetraselmis chuii (mixed) and compared with a live diet (control) of C. cerastosporum, T. chuii and Artemia nauplii. No significant differences (P 〉 0.05) were detected in growth rates, development and quality indexes of larvae fed the three experimental diets. All diets supported survival percentages of 〉90%. Shrimp larvae fed MD and mixed diets had higher specific trypsin activity and soluble protein content than those fed live diet. Amylase activity decreased in larvae fed the mixed and MD apparently due to the carbohydrate composition of the diet. The results indicate that it is possible to substitute a live diet with a microencapsulated one (with a wall composition made up of a polysaccharide blend) in Litopenaeus vannamei mysis.