Influence of Dietary Oil Sources on Muscle Composition and Plasma Lipoprotein Concentrations in Nile Tilapia,Oreochromis niloticus

To investigate the impact of different dietary lipid sources on fillet composition and lipid transport, we conducted a feeding trial and evaluated the proximate composition of muscle tissue, fatty acid profiles, total cholesterol (in muscle and plasma), triglycerides, and lipoprotein concentrations in Nile tilapia, Oreochromis niloticus. Five semi‐purified diets, containing different oils (soybean – SO, corn – CO, linseed – LO, fish – FO, and olive – OO), were supplied to tilapia for 160 d. Fish fed with LO and FO diets had a lower percentage of total lipids in muscle compared with the others (P < 0.05). The highest percentage of protein was found in fish fed with FO diet (P < 0.05). The muscle fatty acid profile was influenced differently by diets (P < 0.05). The group supplemented with SO and CO had a higher concentration of 18:2n‐6, whereas the fish fed with LO diet had a higher level of 18:3n‐3 and those that received the FO diet had more 22:6n‐3 in comparison with those supplemented with vegetable oils. Plasma lipid transport was also affected by the diets: the fish fed with FO diet had higher total cholesterol and high‐density lipoprotein and lower very‐low‐density lipoprotein concentrations (P < 0.05).     

Effect of the addition of Chaetoceros calcitrans,Navicula sp. and Phaeodactylum tricornutum (diatoms) on phytoplankton composition and growth of Litopenaeus vannamei (Boone) postlarvae reared in a biofloc system

The aim of this study was to evaluate the effect of the addition of Chaetoceros calcitrans, Navicula sp. and Phaeodactylum tricornutum (diatoms) on phytoplankton composition and the growth of Litopenaeus vannamei postlarvae reared in a biofloc system . Four treatments were used: BFT (biofloc system without feed and no addition of diatoms); BFT‐F (biofloc system with feed and no addition of diatoms); BFT‐D (biofloc system with the addition of diatoms and no feed); and BFT‐FD (biofloc system with the addition of feed and diatoms), all in triplicate. The shrimp (16 ± 0.02 mg) were stocked at 2500 postlarvae m^?3 and fed a commercial feed. Diatoms were added on the 1st, 5th, 10th and 15th day at a density of 5 × 10⁴ cells mL^?1 for each species. No significant differences (P > 0.05) between treatments were observed for gross primary production, net ecosystem production and water column respiration rate. However, significant differences (P < 0.05) were observed for nitrite, orthophosphate, alkalinity, final weight, weight gain, yield, feed conversion ratio (FCR), phytoplankton and cyanobacteria composition. The BFT‐FD treatment had better performance parameters for final weight (270 mg), weight gain (254 mg), yield (0.67 Kg m^?3) and FCR (0.61), indicating the benefits of the diatoms C. calcitrans, Navicula sp. and P. tricornutum for decreasing cyanobacteria and improving growth of L. vannamei postlarvae reared in biofloc systems.     

Haematologic and immunologic parameters of bullfrogs,Lithobates catesbeianus,fed probiotics

The effects of two probiotics (P₁–Lactobacillus acidophilus, Bifidobacterium bifidum and Enterococcus faecium and P₂–Bacillus subtilis) supplemented to commercial feed (40% crude protein) on the haematological and immunological parameters of the bullfrog Lithobates catesbeianus were studied. Two doses of each probiotic (5 and 10 g kg^?1 of food) were added to the diets and fed to frogs, totalling five treatments over 112 days. Haematological analyses consisted of total and differential leucocyte counts, erythrocyte and thrombocyte counts, haematocrit, haemoglobin levels and RBC indices (mean corpuscular volume, mean corpuscular haemoglobin – and mean corpuscular haemoglobin concentration) and the immunological parameters included phagocytic capacity and phagocytic index of peritoneal phagocytes. The results showed that the probiotics did not significantly influence any of the haematological parameters measured. However, immunological assays showed that the probiotics had an immunostimulating effect. The greatest effects were seen with probiotic P₁ fed at a dose of 10 g kg^?1 of diet and probiotic P₂ fed at 5 g kg^?1 of diet.     

Assessment of induction and recovery times of anaesthesia in Astyanax bimaculatus using 2‐phenoxyethanol and the essential oils of Melaleuca alternifolia and Ocimum gratissimum

This study aimed to determine the lowest effective concentration (LEC) of 2‐phenoxyethanol (2‐Phe) and essential oils (EOs) of Melaleuca alternifolia and Ocimum gratissimum able to induce anaesthesia in Astyanax bimaculatus. LEC was assumed to be the required concentration to carry out anaesthesia in less than 3 min with recovery in <5 min and sufficient to carry out routine aquaculture procedures. The following concentrations were tested: 2‐Phe (100, 200, 300, 400, 500 and 600 µl/L); M. alternifolia (200, 300, 400, 500 and 600 µl/L); and O. gratissimum (10, 20, 30, 40, 50, 60, 70, 100, 150, 250 and 300 µl/L). Results show that all three agents evaluated have effective anaesthetic properties for use in Astyanax bimaculatus with LEC for 2‐Phe, M. alternifolia and O. gratissimum of 200, 300 and 60 µl/L respectively.     

Development of a method for live octopus (Octopus vulgaris) transportation for long distance at high densities

The development of new octopus‐based products with a growing economic value ensures the commercial interest of this species, making live octopus export an activity of great interest. The aim of this study was to develop a method for long‐distance transportation of live octopus at high densities. The system was composed by 220‐L tanks with cooling and aeration, where the animals were kept separated from each others. The water temperature was maintained at 10°C, after a decreasing of 1°C/hr. Live octopus transportation was tested for 48 hr at two densities: 50 kg/m³ and 100 kg/m³. During this period, water parameters were monitored. Stress response was evaluated through the analysis of haemolymph, muscle and brain tissues. No mortality was registered after 48 hr for both treatments. In all trials, water quality remained within the normal limits in both densities; there was, however, a significative increase of ammonia levels in the water. Ammonia, dopamine and Hsp70 levels were analysed in the beginning and at the end of the experiment for both densities; however, no significant differences were found among them. In general, this system seems to be a viable solution for live octopus 48‐hr transportation at a density of 100 kg/m³.     

Pre‐Columbian fisheries catch reconstruction for a subtropical estuary in South America

Small‐scale fisheries provide food and livelihoods for thousands of people along the Brazilian coastline. However, considerable uncertainties still surround the extent to which artisanal and subsistence fisheries contribute to the total of national landings and their historical ecological significance. Fisheries monitoring is deficient in Brazil, and historical records are limited to irregular accounts spanning the last few decades, while this coastline has supported human populations for at least 6,000 years. Here, we estimate pre‐Columbian subsistence catches for a large subtropical estuary in southern Brazil. Our results suggest that prehistoric populations may have extracted volumes of fish biomass higher than or comparable with historical subsistence fisheries in the region, and that the latter is likely underestimated. If a long‐term perspective is required to evaluate the current economic value and status of fisheries in subtropical and tropical South America, this should go beyond the historical time interval and integrate the contribution of pre‐Columbian archaeology.     

Improving the estimation of soil water evaporation based on days after wetting

Soil evaporation constitutes a major pathway of water loss in agriculture. Understanding its dynamics in the face of drying and soil cover is fundamental to improve both simulation models and the sustainability of production systems. Thus, the objective of this study was to estimate soil evaporation as a function of drying and percentage of soil cover. Three experiments were carried out in three different periods. In each of the periods, in parallel and in an adjacent area, an experiment was carried out to evaluate the influence of weighing micro-lysimeter (ML) height on the estimation of direct soil evaporation. The experiments were installed with a completely randomized design. For the experiments that measured evaporation as a function of cover, the treatments consisted of six different percentages of cover of the internal area of the ML (0%, 10%, 25%, 50%, 75% and 100%), with four replicates, using artificial plants to cover the soil. The experiments that estimated evaporation as a function of ML height were conducted with eight repetitions and three different ML heights (100, 200 and 300 mm). It was observed that the accumulated evaporation up to 25 days after wetting was 52% and 53% lower in micro-lysimeters with 100 mm height, compared to those with 200 and 300 mm height, respectively, for all experiments. The new model developed to calculate soil evaporation as a function of the days after wetting and percentage of soil cover showed excellent performance (NSE > 0.95).     

Evaluation of the Microalgae Paste Viability Produced in a Mollusk Hatchery in Southern Brazil

The present study was conducted to define a methodology to produce and store small‐scale microalgae paste to be used in a mollusk hatchery. Microalgae were cultured in 500 L fiberglass tanks, under temperature of 20 ± 2 C, Guillard f/2 culture medium, and continuous light intensity of 203–226 μmol photons/m²/sec. Cultures were centrifuged at 2000 g at the exponential growth phase. Microalgae cell quality after centrifugation and during storage was determined by analyses with Evan’s blue stain and by counting the number of total marine bacteria. Treatments with and without additive were applied to the microalgae paste produced, which was distributed into 100 mL plastic containers, capped, and stored under refrigeration at 4 ± 1 C. Results indicated that in the Chaetoceros muelleri paste, centrifugation did not damage the cells and the number of total marine bacteria reduced significantly from 2.9 × 10⁶ to 8.3 × 10⁵ colony‐forming units per milliliter. Chaetoceros muelleri and Chaetoceros calcitrans pastes stored with addition of 0.1% ascorbic acid had a shelf life shorter than 2 wk. For the treatment without additive, results with Evan’s blue stain showed that cells (99%) remained viable until the sixth week of storage for C. muelleri and seventh week of storage for Skeletonema sp. and C. calcitrans. The number of bacteria did not increase during storage for C. calcitrans and Skeletonema (P > 0.05). For C. muelleri, an increase in bacteria (P < 0.05) was observed after the sixth week of storage. This study demonstrated the feasibility to produce and store microalgae paste for a period of 2–8 wk, which allows it to be used as food source and also optimizes the use of microalgae cultured in laboratory.     

Surface liming effects on soil radiation attenuation properties

Purpose

This study investigates the effects of surface liming on soil attenuation radiation properties. For this, measurements of soil chemical attributes (pH, organic carbon, H+Al, Al³⁺, Ca²⁺, and Mg²⁺) and attenuation radiation parameters (mass attenuation coefficient, μ_m, atomic and electronic cross sections, σ_a and σ_e, effective atomic number and electron density, Z_eff and N_el) were carried out. This aim was motivated by the fact that possible μ_m variation might cause as well variation in the determination of soil physical properties.

Materials and methods

The studied soil, classified as a Dystrudept sity-clay, is located in South Brazil. The trial consisted of five stripes, one of them under pasture and the remaining under no-till system (NTS). Lime rates of 0, 10, 15, and 20 t ha^?1 were broadcast on the NTS soil surface. Disturbed soil samples were collected 30 months after liming at the top (0–10 cm) and subsoil (10–20 cm) layers. Soil chemical attributes were characterized following standard experimental procedures. The soil oxide composition, obtained by EDXRF analysis, was used to calculate μ_m for ²⁴¹Am and ¹³⁷Cs photon energies with XCOM computer code. μ_m values were employed to calculate σ_a, σ_e, Z_eff, and N_el and to predict variations in soil bulk density (ρ) and total porosity (φ).

Results and discussion

Surface liming notably increased contents of soil pH, Ca²⁺, and Mg²⁺ while reduced H+Al and Al³⁺ at the top soil layer, where μ_m, σ_a, σ_e, and Z_eff were also increased with the lime rates. However, at the subsoil layer, liming neither lessened soil acidity nor induced remarkable changes in the attenuation parameters. When using ¹³⁷Cs photon energy, incoherent scattering totally dominated over the radiation interaction processes whereas photoelectric absorption and coherent scattering substantially contributed when ²⁴¹Am photon energy was used. Therefore, the increasing in soil attenuation parameters at the top soil layer was more accentuated considering ²⁴¹Am than ¹³⁷Cs photon energy. Variation in μ_m caused considerable variation in ρ and φ only for ²⁴¹Am photon energy.

Conclusions

The findings regarding the effect of μ_m variation induced by liming on the determination of soil physical properties are extremely relevant because traditionally, in the soil science area, μ_m values are calculated without considering any chemical modification to which the soil can be submitted. Bearing in mind that ρ and φ are important parameters from the agricultural and environmental points of view, not representative measurements of μ_m can lead to biased values of ρ and φ.