Ronaldo Olivera Cavalli

Performance of Macrobrachium rosenbergii broodstock fed diets with different fatty acid composition

Abstract The effect of linoleic acid (18:2 n −6) and n −3 highly unsaturated fatty acids (HUFA) on the reproductive performance and offspring quality of the freshwater prawn Macrobrachium rosenbergii was evaluated in a 180-day trial. Three isonitrogenous and isolipidic diets containing different levels of fatty acids, high 18:2 n −6 and n −3 HUFA concentrations, high 18:2 n −6 and low n −3 HUFA, and low 18:2 n −6 and n −3 HUFA, were fed ad libitum to three groups of six females. Fecundity was improved by the addition of higher amounts of 18:2 n −6 (from 3 to 13 mg g −1 DW). As a consequence of higher fecundity, smaller eggs were obtained most likely because the number of oocytes competing for a limited amount of yolk was higher. The higher gonado-somatic index of females fed diets with high levels of 18:2 n −6 and n −3 HUFA levels further supports this hypothesis. The fatty acid composition of the eggs reflected to some extent the composition of the diets. Eggs of females fed high levels of 18:2 n −6 and n −3 HUFA had the highest n −3 HUFA content and had increased hatchability. Eight-day-old larvae from females fed high levels of 18:2 n −6 and n −3 HUFA tended to present a better stress tolerance when exposed to 100 mg l −1 total ammonia for 24 h. No other differences were detected among larval characteristics from the different offspring groups. Results demonstrate that feeding M. rosenbergii broodstock with high levels of 18:2 n −6 and n −3 HUFA (13 and 15 mg g −1 DW, respectively) improved fecundity, egg hatchability, and the overall quality of the larvae.

Variations in lipid classes and fatty acid content in tissues of wild Macrobrachium rosenbergii (de Man) females during maturation

Abstract This study describes the variations in total lipid, lipid classes and fatty acids in the midgut gland (MG), ovary, and muscle tissue of wild-caught Macrobrachium rosenbergii to elucidate the importance of these components during sexual maturation. Mature females were captured in the Mae Klong River, Thailand, from July to September 1998, and divided into five groups according to their ovarian development. Total lipid levels in the ovary increased with maturation, but no concomitant decrease in MG lipids was observed. Thus, the lipid requirements of the developing ovary are thought to be more dependent on the immediate ingestion of dietary lipid than on MG reserves. Higher proportions of neutral lipids (NL), mainly triacylglycerols (TG), were observed in both MG and ovary, whereas polar lipids (PL) predominated in muscle. In the ovary, total NL increased significantly along with maturation mainly due to an increase of TG and sterols. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) formed the bulk of ovarian PL and also increased significantly as maturation progressed. Major fatty acids in both MG and ovary were 14:0, 16:0, 18:0, 18:1 n −9, 18:2 n −6, 18:3 n −3, 20:4 n −6, 20:5 n −3 and 22:6 n −3. Significant increases in the levels of saturated and mono-unsaturated fatty acids were observed in both MG and ovary. The levels of n −3 highly unsaturated fatty acids (HUFA), particularly 20:5 n −3, decreased in the MG as ovarian development proceeded. In contrast, an increase in the ovarian contents of n −3 HUFA was detected.

Ammonia toxicity as a criterion for the evaluation of larval quality in the prawn Macrobrachium rosenbergii

The feasibility of a short-term ammonia toxicity test as an evaluation criterion for larval quality was assessed in three trials. In each one, Macrobrachium rosenbergii larvae originating from the same spawn were nutritionally differentiated in two groups by feeding them either a nutrient-rich (Artemia nauplii enriched for 24 h with n-3 highly unsaturated fatty acids (HUFA) and ascorbic acid (AA)) or a nutrient-poor diet (Artemia nauplii starved for 24 h). Throughout their development, larvae from both treatments were exposed during 24 h to six concentrations of total ammonia (NH(4)(+)+NH(3)) and a control (no ammonia added). Based on mortality rates, the median lethal concentration for 50% of the population (LC(50)) was estimated. As expected from earlier work, larvae fed the optimal diet presented higher n-3 HUFA and AA contents as well as higher growth and metamorphosis rates. From the moment the effect of diet quality was analytically detectable in the tissues of the larvae, the ammonia test was able to distinguish both groups of larvae. Differences in ammonia tolerance were observed as early as larval stage 4 and remained evident throughout larval development. The short-term ammonia toxicity test proved to be a valuable, sensitive and reproducible criterion for the establishment of larval quality.

Maturation performance, offspring quality and lipid composition of Macrobrachium rosenbergii females fed increasing levels of dietary phospholipids.

The effects of increasing levels of dietaryphospholipids (PL) on the reproductive performance,egg and larval quality, and lipid composition offemales of the freshwater prawn Macrobrachiumrosenbergii were investigated. Three isolipidic dietscontaining similar amounts of highly unsaturated fattyacids but varying levels of PL (0.8, 2.4 and 4.6%)were fed during 180 days to three groups of eightfemales originating from Thai ponds. No significantdifferences were observed for fecundity, egg size andhatchability, starved larvae size, and size, survivaland tolerance to stress of 8 day-old larvae.Similarly, no major differences in the lipidcomposition of the midgut gland, ovaries and muscletissue of females could be detected. Results indicatethe lack of need of dietary supplementation of PL forM. rosenbergii broodstock, as previouslyreported for earlier life stages. It is suggested thatthe basal level of 0.8% dietary PL was sufficient tomeet the dietary demands of the prawn broodstock. ThePL requirements of M. rosenbergii broodstock, ifany, may be satisfied in commercial feeds through theinclusion of ingredients containing some phospholipidsendogenously.

Effect of dietary supplementation of vitamins C and E on maternal performance and larval quality of the prawn Macrobrachium rosenbergii

Abstract The effects of vitamin C (ascorbic acid, AA) and vitamin E (tocopherol) on the maternal performance and offspring quality of the freshwater prawn Macrobrachium rosenbergii were investigated. Prawn females were fed four diets containing different levels of 2-ascorbyl- l -polyphosphate (ApP) and α-tocopherol acetate (α-TA) during 155 days. Three diets contained increasing AA levels (59, 121 and 918 μg g −1 DW) and a basal level of α-TA (around 300 μg g −1 DW), while a fourth diet contained comparatively higher α-TA levels (899 μg g −1 DW) combined with 957 μg AA g −1 DW. Higher dietary levels of AA and α-TA did not affect moulting, growth, or mortality rates of the broodstock. Also, breeding frequency and fecundity were not related to the dietary treatments. However, the contents of AA and α-tocopherol in the midgut gland, ovary, eggs, and newly hatched larvae increased along with higher dietary levels of these vitamins. Larvae from females fed higher levels of AA and α-TA tended to present an increased tolerance when exposed to increasing ammonia concentrations. The present results therefore suggest that broodstock diets containing around 60 μg AA g −1 DW and 300 μg α-TA g −1 DW are sufficient to ensure proper reproduction and offspring viability. However, feeding M. rosenbergii females higher dietary levels of both AA and α-TA (each around 900 μg g −1 DW) might increase larval quality, as demonstrated in this study by the higher tolerance to the exposure to ammonia.

The Challenge of Sustainable Aquaculture: Effects on the Environment of the Patos Lagoon Estuary

Abstract Over the last ten years, catches of the pink shrimp Farfantepenaeus paulensis by artisanal fishermen in the Patos Lagoon Estuary (southern Brazil) have been decreasing. This has created economic and social problems for approximately 3500 families, who rely on this activity as their main source of income. In an attempt to solve these problems, the Mariculture Laboratory of the University of Rio Grande (FURG) has developed a technological package for the pen culture of this species in the estuarine area. This culture system requires low investment, is easy to manage and allows fishermen to continue their normal activities. This study evaluates the influences that this culture may have on the macrobenthic communities surrounding the enclosures. The experiment was carried out around a 0.3 ha pen placed in the estuarine area adjacent to Marinheiros Island (Rio Grande county). This area has a central channel over 5 meters deep and shallow areas less than 1.5 meters deep near the shore, where the pen was installed. Two linear transects were carried out in opposite directions parallel to the shoreline, starting from the edge of the pen. Monthly water and sediment samples were collected 5, 15, 30 and 100 m from the pen to evaluate oxygen consumption, chlorophyll-a, total phosphorus and total nitrogen concentrations. Characterization of the macrobenthic community revealed the presence of Laeonereis acuta, Nephtys fluviatilis, Neanthes sp., Kalliapseudes schubartii, Callinectes sapidus, Erodona mactroides, Heleobia australis, Heteromastus similis and isopods. Significant differences in the diversity and abundance of the species were detected between the samples, especially at the closest point to the pen, where more H. similis specimens were found. No significant differences in oxygen consumption, total nitrogen or total phosphorus concentrations were found between the sampled points. These results demonstrate that this kind of culture system does not influence water quality in the surrounding area. The higher abundance of H. similis near the pen (1 m) demonstrated a very limited impact on the macrobenthic community. Organic matter accumulation zones created by the presence of the pen might favor the presence of H. similis, which is a deposit feeder. This result could become more significant if the culture conditions are intensified or more pens are installed.