Density and Water Exchange-Dependent Growth and Survival of Litopenaeus setiferus Postlarvae

This present study was designed to investigate the effects of stocking density and water exchange on the growth rate, survival and performance index of L. setiferus postlarvae under controlled laboratory conditions. The experiment was done with postlarvae (PL10 to PL40) at densities of 50, 150, 250 and 350 shrimp/m² and various different water exchanges rate per day (0, 6, 12 and 18%). The maximum growth rate was obtained for shrimp with 12% water exchange per day at all densities. A reduction of the maximum growth rate was observed in relation to density with the highest values in shrimp stocked in a density of 50 and 150 shrimp/m² (mean value of 0.53 mg/d) and the lowest in shrimp stocked in a density of 350 shrimp/m² (0.24 mg/d). The multiple regression equation obtained to relate performance index (growth rate* survival : PI), shrimp density (X₁) and water exchange (X₂) was: PI = 0.31 + (0.001) X₁+ 0.039 X₂+ 2.28 × 10⁻⁶ X₁²+ (−0.0017) X₂²+ (0.000026)X₁X₂, R ²= 0.78; P > 0.03. According to this equation the optimum shrimp density-water exchange comhination was between 5 to 12% of water exchange at stocking density of between 50 and 150 shrimp/m². Salinity, ammonia-N and nitrite-N increased according to the time spent in tanks without water exchange. With no (0%) water exchange, water quality parameters measured were outside the optimum for L. setiferus postlarvae. The use of optimum density and water exchange in a nursery system for L. setiferus with optimum variables established is proposed.     

Changes in forest structure modify understory and livestock occurrence along the natural cycle and different management strategies in Nothofagus antarctica forests

Agroforestry Systems - Sustainable forest management is proposed as a solution for many ecological and socio-economic trade-offs associated with different forest uses. In Patagonia, silvopastoral...     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

Growth and survival of juvenile spider crabs,Maja brachydactyla (Balss, 1922), fed with fresh or frozen mussels

The effects of diet freezing on the growth, survival and biochemical composition of the diets and juvenile spider crabs (Maja brachydactyla) were studied. Fresh and frozen (at ?20 °C for 21 days) mussels, Mytilus edulis, were used as food. Two experiments were conducted and in each, spider crabs were placed in individual trays. During experiment I, 40 juvenile spider crabs (2 months old) were used. Twenty animals (9 ± 2 mg) were fed fresh mussels, and 20 animals (8 ± 2 mg) were fed frozen mussels. Spider crabs fed fresh mussels grew larger than the ones fed frozen mussels (304.0 ± 118.0 and 70.0 ± 40.1 mg respectively). During experiment II, 16 juvenile spider crabs (5 months old) were used. Eight animals (3.4 ± 0.8 g) were fed fresh mussel and eight animals (4.1 ± 1.3 g) were fed frozen mussel. Spider crabs fed with fresh mussels were larger than the ones fed with frozen mussels (92.5 ± 41.7 and 41.5 ± 17.7 g respectively). There were no significant differences in the protein, amino acids and fatty acid composition between fresh and frozen mussels. The freezing procedure makes mussels less adequate for the culture of 2‐month‐old early juveniles of M. brachydactyla up to 5 months, although they promoted acceptable growth and good survival in older animals (>5 months old).     

Effect of temperature increase on the embryonic development of Patagonian red octopus Enteroctopus megalocyathus in controlled culture

One of the major problems involved in the controlled cultivation of Patagonian red octopus (Enteroctopus megalocyathus) is its long embryonic period ranging between 150–176 days, after which the hatching of planktonic paralarvae is achieved. The effect of temperature on the incubation of E. megalocyathus eggs was studied with the aim of establishing if a temperature higher than 12°C is effective to accelerate the embryonic development without altering their morphological and physiological conditions. Fertilized eggs obtained under controlled conditions at 11°C ± 0.1 were randomly distributed in 12 water baths of 30 L at 4 temperatures: 12, 14, 15 and 16°C ± 0.1°C. The experiment lasted until egg hatching occurred.The embryo growth rate was accelerated at 15–16°C, so the time spent in embryonic development can be reduced in 15% when compared with embryo development obtained from eggs incubated at 12°C. The embryos showed no significant differences in the final survival and were morphometrically similar in all stages of development at all temperatures. The increase in temperature from 12 to 16°C, even if it allowed a better growth, had high metabolic costs for embryos of E. megalocyathus. The activities of lipases and proteases were affected by interaction between temperature and the embryo stage, with high lipase activity observed in embryos of stage XV incubated at high temperatures and the highest levels of trypsin and chymotrypsin in stage XX at 14°C. The results suggest that 15°C could be the limit temperature to increase growth.     

Arabidopsis thaliana,an experimental host for tomato yellow leaf curl disease‐associated begomoviruses by agroinoculation and whitefly transmission

Tomato yellow leaf curl disease is one of the most devastating viral diseases affecting tomato crops worldwide. This disease is caused by several begomoviruses (genus Begomovirus, family Geminiviridae), such as Tomato yellow leaf curl virus (TYLCV), that are transmitted in nature by the whitefly vector Bemisia tabaci. An efficient control of this vector‐transmitted disease requires a thorough knowledge of the plant–virus–vector triple interaction. The possibility of using Arabidopsis thaliana as an experimental host would provide the opportunity to use a wide variety of genetic resources and tools to understand interactions that are not feasible in agronomically important hosts. In this study, it is demonstrated that isolates of two strains (Israel, IL and Mild, Mld) of TYLCV can replicate and systemically infect A. thaliana ecotype Columbia plants either by Agrobacterium tumefaciens‐mediated inoculation or through the natural vector Bemisia tabaci. The virus can also be acquired from A. thaliana‐infected plants by B. tabaci and transmitted to either A. thaliana or tomato plants. Therefore, A. thaliana is a suitable host for TYLCV–insect vector–plant host interaction studies. Interestingly, an isolate of the Spain (ES) strain of a related begomovirus, Tomato yellow leaf curl Sardinia virus (TYLCSV‐ES), is unable to infect this ecotype of A. thaliana efficiently. Using infectious chimeric viral clones between TYLCV‐Mld and TYLCSV‐ES, candidate viral factors involved in an efficient infection of A. thaliana were identified.     

Oxygen consumption and ammonia-N excretion related to protein requirements for growth of white shrimp, Penaeus setiferus (L.), juveniles

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.     

Digestive dynamics during chyme formation of Octopus maya (Mollusca,Cephalopoda)

In the present study, digestive dynamics, measured through the changes in the in situ pH along the digestive tract, was evaluated along with the glycogen concentration in the digestive gland (DG) and the proteolytic enzyme activity of the gastric juice (GJ) (both acid and alkaline proteases) to obtain useful information that will allow for the understanding of the DG's function and the role that it plays as an extracellular digestive enzyme source and for energy storage, providing new information on the digestive physiology of Octopus maya. The results showed that pH along the digestive tract changed according to the postprandial time following the food transit. At the beginning, the pH on crop (St) was 5, changing to 6 when the food arrived. Similar changes were observed on the caecum (Ce) and DG. Glycogen from DG is used as a source of energy during digestion and recovered 8 h after feeding. Maximum activities of digestive gland GJ enzymes were observed 6 h after feeding, indicating that chyme enzymes are still active when they arrive at the DG's lumen. The presence of food in the digestive tract modifies the pH, which, in combination with GJ, favours the activity of the released enzymes of O. maya.     

Energy Balance of Callinectes rathbunae Contreras 1930 in Floating Cages in a Tropical Coastal Lagoon

The genus Callinecres is ecologically important in the coastal lagoon region of the Gulf of Mexico. This study was conducted to test the feasibility of raising these crabs in a system of floating cages and to measure their scope for growth in a tropical coastal lagoon of the Gulf of Mexico. The equation P = As - (R + E + N) was used to estimate the scope for growth (P) for C. rathbunae under experimental conditions for 21 days. Ingested food was 3% of body weight. Assimilation (As) was 73% of assimilated energy, 21.4% was channeled to respiration (R), 2% to excretion (N) and 0.16% to exuvia (E). The remainder of the energy was channeled to growth at a net efficiency of 76%. Significant differences were not found between the calculated scope for growth and the growth achieved in the culture system ( P > 0.05). These results support the energy balance equation and suggest that the cultivation of C. rathbunae in floating cages is possible.     

Lethal Low Dissolved Oxygen Concentrations for Postlarvae and Early Juvenile Penaeus setiferus at Different Salinities and pH

Abstract This study was undertaken to determine the effect of salinity and pH on tolerance to low dissolved oxygen concentration in postlarval (PL 12; 18 mg wet weight) and early juvenile (720 mg wet weight) Peneaus setiferus . Lethal levels of dissolved oxygen were determined in animals at four combinations of salinity and pH (36 and 15 ppt salinity and pH 6 and 8). For postlarvae, the 48-h LC50 for dissolved oxygen was 1.27 mgO₂/L at 15 ppt and pH8, and was significantly lower than that obtained in the other combinations of salinity and pH (P < 0.05). For juveniles, the 72-h LC50 was 1.16 mg1L at 15 ppt and pH 8, and was significantly lower than that obtained in the other combinations of salinity and pH (P < 0.05). A significant interaction between salinity and pH was observed. These results suggest that the intensive culture of P. setiferus may be conducted at moderate salinity, where shrimp appear to be more tolerant of low concentrations of oxygen than at higher salinities.