Evaluation of frozen Umbrella‐stage Artemia as first animal live food for Litopenaeus vannamei (Boone) larvae

An alternative larval shrimp feeding regime, in which umbrella‐stage Artemia were constituting the first zooplankton source was evaluated in the culture of Litopenaeus vannamei. In a preliminary experiment, umbrella‐stage Artemia were fed to larvae from zoea 2 (Z2) to mysis 2 (M2) stages to identify the larval stage at which raptorial feeding starts and to determine daily feeding rates. The following experiment evaluated the performance of two feeding regimen that differed during the late zoea/early mysis stages: a control treatment with frozen Artemia nauplii (FAN), and a treatment with frozen umbrella‐stage Artemia (FUA). The ingestion rate of umbrella‐stage Artemia increased from nine umbrella per larvae day^?1 at Z2 stage to 21 umbrella per larvae day^?1 at M2. A steep increase in ingestion and dry weight from Z3 to M2 suggests a shift to a raptorial feeding mode at the M1 stage. Treatment FUA exhibited a significantly higher larval stage index (P < 0.05) during the period that zoea larvae metamorphosed to the mysis stage, and a higher final biomass, compared with treatment FAN. Based on these results and on practical considerations, a feeding regime starting with umbrella‐stage Artemia from Z2 sub‐stage can be recommended for L. vannamei larvae rearing.     

The Effect of Live and Artificial Diets on Growth, Survival, and Trypsin Activity in Larvae of Penaeus indicus

In this study, partial and total replacement of live diets (microalgae and Artemia nauplii) with microencapsulated diets (MED) are demonstrated for larval culture of P. indicus . Slower growth and lower survival rate of larvae fed experimental MED were significantly improved by a supplement of 15 cells/μL frozen mixed algae (1:2, Tetrtaselmis and Skeletonema ) during protod stages (PZ1–PZ3). This low level of algal supplement to MED resulted in survival (85–92%) equal to that obtained from control live diets (91%) during protod stages. These significant improvements in larval growth and survival are likely to be due to higher larval digestive enzyme activities and hence more efficient digestion of the artificial diet by the larvae. Like other penaeids, P. indicus larvae show high total and tissue trypsin activities during PZ stages, with a peak at mysis stage 1 (M1), and a decrease during subsequent stages when fed on conventional live diets of algae followed by Artemia during mysis stages. Larvae fed 15 ceUs/μL mixed frozen algae in addition to MED demonstrated a significantly higher trypsin activity throughout herbivorous larval stages in comparison to larvae fed solely on MED. A freeze dried alga Rhinomonas reticulata incorporated into a MED at 23Vo (v/v) induced larval trypsin activity equal to that produced by live algae. Hence, the algal substances, which trigger digestive enzyme production, may be retained within the microcapsules. At mysis stages, however, addition of live prey (one Artemia/ mL) to cultures fed with MED significantly improved growth and survival although it depressed trypsin activity. For mysis stages it appears that the use of predigested ingredients is necessary to improve the digestibility of formulated diets.     

Successful culture of larvae of Litopenaeus vannamei fed a microbound formulated diet exclusively from either stage PZ2 or M1 to PL1

In three separate experiments, harpaticoid copepods Tisbe monozota (alive and dead) and a microparticulate microbound diet were evaluated as alternatives to live Artemia nauplii as food, beginning at either stage PZ2 or M1, in the larval culture of Litopenaeus vannamei. Larvae were cultured in 2 L round bottom flasks at a density of 150 L^− 1 (Experiment 1) and 100 L^− 1 ( 3.2 and 3.3) at 28 °C, 35‰ salinity and 12:12 LD photoperiod, and fed 4×/day^- 1. Larvae were initially fed a mixture of phytoplankton to stages PZ2 or M1 and then fed either live Artemia, live or dead copepods, or a microparticulate microbound diet. The experiments were terminated and all larvae were harvested when more than 80% of larvae had molted to postlarvae 1 (PL1) within any flask representing any of the treatments. The comparative value of the different diets and feeding regimes was determined by mean survival, mean dry weight and total length of individual larva, and percentage of surviving larvae that were PL1. Trypsin activity of samples of larvae from each treatment was also determined. The microparticulate microbound diet effectively served as a complete substitute for Artemia nauplii when fed beginning at stage M1. When fed at the beginning of the PZ2 stage, survival was comparable to that of larvae fed Artemia, but mean dry weight, mean total length, and percent of surviving larvae that were PL1 generally were significantly less. Responses to the feeding of copepods, whether fed dead or live, as a substitute were generally significantly less than those of larvae fed either the Artemia nauplii or the microparticulate diet. Values of trypsin activity (10^− 5 IU/μg^- 1 dry weight) corresponded to the relative proportions of the different larval stages within a treatment, with higher activity being characteristic of early stages. Previously demonstrated successful results with another species of crustacean suggest that the microparticulate microbound diet has characteristics that should be effective in the culture of the carnivorous stages of other crustacean and fish larvae that are currently fed live Artemia nauplii.     

Larval growth, survival and development of Metapenaeus monoceros (Fabricius) cultured in different salinities

Larvae of Metapenaeus monoceros (Fabricius) at protozoea 1 (PZ1) stage were stocked in 2‐L glass flasks to investigate the effects of various salinities (25, 30, 35, 40, 45, 50 and 55 ppt) on growth and survival until the post‐larval (PL) stages. The PZ larvae were not able to tolerate a sudden salinity drop of over 10 ppt. Yet, an abrupt salinity increase of over 10 or even 15 ppt did not cause mortality. The PZ larvae were successfully acclimated to different test salinities at a rate of 4 ppt h^?1. The larvae displayed better tolerance to high rather than low salinities. The lowest and highest critical salinities appeared to be 22 and 55 ppt respectively. Taking into account survival, growth and development results, the optimal salinity for the larval culture of M. monoceros inhabiting the Eastern Mediterranean was 40 ppt. At this salinity, the PZ1 larvae were successfully cultured until PL1 stage within 11 days with 68% survival on a feeding regime of Tetraselmis chuii Kylin (Butcher) (20 cells μ L^?1), Chaetoceros calcitrans Paulsen (50 cells μ L^?1), Isochrysis galbana Parke (30 cells μL^?1) and five newly hatched Artemia nauplii mL^?1 from M1 onwards at 28 °C.     

Predation and energetics of Penaeus indicus (Decapoda: Penaeidae) larvae feeding on Brachionus plicatilis and Artemia nauplii

Brachionus plicatilis and Artemia nauplii were fed to a number of larval stages of the penaeid prawn Penaeus indicus to determine ingestion rates, larval energy requirements and to establish at which stage larval predation commenced. The raptorial feeding rates were then contrasted on an energy basis with filter feeding rates for P. indicus larvae to compare the relative efficiency of these two feeding mechanisms. Brachionus was first eaten as early as protozoea 1 to protozoea 2, while the maximum ingestion rate of 300 rotifers larva^?1 d^?1 (1.06 J larva^?1 d^?1) was obtained during protozoea 3 to mysis 1. Artemia were effectively ingested by P. indicus protozoea 3 (4.1 J larva^?1 d^?1) to post-larva (8.2 J larva^?1 d^?1). Daily energy intake rate from filter feeding increased from 1.1 J larva^?1 d^?1 during protozoea 1 to reach a peak of 5.32 J larva^?1 d^?1 during mysis 3 after which it declined to 2.66 J larva^?1 d^?1 during the post-larval stage. This decline in energy intake from filter feeding with a concomitant increase in energy intake from Artemia predation demonstrates a predominant feeding mode changeover point during mysis 3. Energy intake was consistently low with Brachionus, indicating that it may be unnecessary for commercial culture purposes.     

Growth, survival, quality and digestive enzyme activities of larval shrimp fed microencapsulated, mixed and live diets

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.     

Ammonia tolerance of Litopenaeus vannamei (Boone) larvae

The tolerance of Litopenaeus vannamei larvae to increasing concentrations of total ammonia nitrogen (TAN) using a short‐term static renewal method at 26°C, 34 g L^?1 salinity and pH 8.5 was assessed. The median lethal concentration (24 h LC₅₀) for TAN in zoea (1‐2‐3), mysis (1‐2‐3) and postlarvae 1 were, respectively, 4.2‐9.9‐16.0; 19.0‐17.3‐17.5 and 13.2 mg L^?1TAN (0.6‐1.5‐2.4; 2.8‐2.5‐2.6 and 1.9 mg L^?1 NH₃‐N). The LC₅₀ values obtained in this study suggest that zoeal and post‐larval stages are more sensitive to 24 h ammonia exposure than the mysis stage of L. vannamei larvae. On the basis of the ammonia toxicity level (24 h LC₅₀) at zoea 1, we recommend that this level does not exceed 0.42 mg L^?1 TAN – equivalent to 0.06 mg L^?1 NH₃‐N – to reduce ammonia toxicity during the rearing of L. vannamei larvae.     

Successful rearing of whiteleg shrimp Litopenaeus vannamei larvae fed a desiccation‐tolerant nematode to replace Artemia

The nematode Panagrolaimus sp. was tested as live feed to replace Artemia nauplii during first larval stages of whiteleg shrimp Litopenaeus vannamei. In Trial 1, shrimp larvae were fed one of four diets from Zoea 2 to Postlarva 1 (PL1): (A) Artemia nauplii, control treatment; (NC) nematodes enriched in docosahexaenoic acid (DHA) provided by the dinoflagellate Crypthecodinium cohnii; (N) non‐enriched nematodes; and (Algae) a mixture of microalgae supplemented in C. cohnii cells. In Trial 2, shrimp were fed (A), (NC) and a different treatment (NS) with nematodes enriched in polyunsaturated fatty acids (PUFAs) provided by the commercial product S.presso^®, until Postlarva 6 (PL6). Mysis 1 larvae fed nematodes of the three dietary treatments were 300 μm longer (3.2 ± 0.3 mm) than control larvae. At PL1, control shrimp were 300 μm longer (4.5 ± 0.3 mm) than those fed DHA‐enriched or PUFAs‐enriched nematodes. No differences were observed in length and survival at PL6 between control larvae and those fed DHA‐enriched nematodes (5.1 ± 0.5 mm; 33.1%–44.4%). Shrimp fed microalgae showed a delay in development at PL1. This work is the first demonstration of Panagrolaimus sp. suitability as a complete substitute for Artemia in rearing shrimp from Zoea 2 to PL6.     

Feeding and digestion in the caridean shrimp larva of Palaemon elegans Rathke and Macrobrachium rosenbergii (De Man) (Crustacea: Palaemonidae) on live and artificial diets

Larvae of two caridean shrimp species, Macrobrachium rosenbergii (De Man) and Palaemon elegans Rathke, were fed live and artificial diets. P. elegans larvae fed exclusively live Artemia salina (15 nauplii mL^?1) developed into first postlarval stage (PL1) within 12 days at a temperature of 25°C and salinity 32.5 g L^?1. Their survival and mean total length at this stage were 88.5% and 6.7 mm respectively. M. rosenbergii larvae fed on 15 Artemia mL^?1 started to metamorphose into PLl within 24 days at 29–30°C and 12 g L^?1. Attempts to completely replace live Artemia for rearing P. elegans during early stages failed, and only a partial replacement was achieved for the larvae of both species. P. elegans larvae survived (49%) solely on a microgranulated diet (Frippak PL diet) from stage zoea (Z) 4–5 to PL1. Similarly, a microencapsulated diet (Frippak CD3) also sustained M. rosenbergii larvae from Z5–6 to PL1 with a 28% survival. Development of the larvae of both species was retarded by 2–3 days and their survivals were lower than those fed on the live diet. The inability of the early larvae of these caridean species to survive on artificial diets is attributed to their undeveloped guts and limited enzymatic capabilities. Trypsin activity in the larvae was determined for all larval stages. It was found that the highest trypsin activity, at stage Z4–5 in P. elegans and at stage Z5–6 in M. rosenbergii, coincides with a rapid increase in the volume of the hepatopancreas and the formation of the filter apparatus. These morphological changes in the gut structure appear to enable the larvae to utilize artificial diets after stage Z5–6. Low larval trypsin activities may be compensated by the easily digestible content of their live prey during early larval stages (Z1–Z4/5) and by longer gastroevacuation time (GET) and almost fully developed guts during later stages.     

Effect of different diets on growth and digestive enzyme activity in Litopenaeus vannamei (Boone, 1931) early post-larvae

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.     

Evaluation of microalgae diets for Litopenaeus vannamei larvae using a simple protocol

We evaluated native marine microalgae isolated from NortheasternVenezuela, as food for Litopenaeus vannamei larvae,compared to six microalgae commonly used in aquaculture. We evaluated themicroalgal ingestability calculating the biomass consumed by larvae, later weevaluated three monoalgal diets on protozoea stages of L.vannamei over 72 hr based on the larval biomass,RNA/DNAindex and the proportion of stage retarded larvae. The presence of everymicroalgae species in the protozoea's digestive tract indicated theirconsumption. Chaetoceros spp. showed high ingestabilityandTetraselmis spp. and Skeletonema sp.Ch1 showed low ingestability. The native microalgaeChaetoceros sp. A1 and Chaetocerossp.G1 were evaluated as monoalgal diets compared to Chaetocerosgracilis. Ch. gracilis demonstrated the bestresults when the evaluation was performed with the RNA/DNA index. However, thesurvival rate, larval biomass and percentage of stage retarded larvae fed withChaetoceros sp. G1 were not statistically different fromthose fed with Ch. gracilis. Taking into account thatnative microalgae produced higher biomass in shorter times when they werecultured in field conditions, the results suggest that native microalgae areadequate for large-scale culture conditions, thus reducing costs. Thedetermination of microalgal size and the larval consumption, dry and organiclarvae biomass and specially the RNA/DNA index, were valuable features of thisevaluation. The protocol developed in this study could be used to evaluatemicroalgae quality under different environmental conditions and productionregimes.     

Use of the Nematode Panagrellus redivivus as an Artemia Replacement in a Larval Penaeid Diet

Penueus vannumei larvae (P₂ through M₃) and early postlarvae (<24 h old postlarva) were fed diets consisting of algae-only, nematodes ( Panugrellus redivivus ) plus algae or Artemia plus algae. Growth (dry biomass gain) of second and third stage protozoea larvae fed the nematodealgae diet was significantly better than that of larvae fed the Artemia-algae diet. From the first mysis through the postlarval substage (<24 h old), growth of shrimp fed the nematodealgae diet equalled that of larvae fed the Artemia-algae diet. All larval substages fed nematodes plus algae accumulated significantly greater biomass than those fed a diet of only algae. Survival and percent metamorphosis of larvae fed nematodes plus algae did not differ significantly from that of larvae fed either Artemia plus algae or algae alone. A nematodealgae feeding regime, which potentially yields growth, survival and metamorphosis equal to that obtained on the standard Artemia plus algae regime, is proposed for P. vannamei .     

Larval quality in relation to consecutive spawnings in white shrimp Litopenaeus vannamei Boone

In this study, we determined the influence of the time broodstock spend in reproduction, and the effect of consecutive spawnings (spawning order) on larval quality of Litopenaeus vannamei. Spawns were sampled at days 1–4, 18–20 and 38–40 after unilateral eyestalk ablation and ordered according to the number of spawns or spawning order (1–11) of each female. Larvae were reared individually to 2‐day‐old postlarvae (PL2); spawn and larval quality was determined in terms of fecundity, fertilization, hatching, morphometric traits, ammonium stress resistance applied at zoea, salinity stress resistance applied at postlarval stages, and survival during culture. Fecundity was not affected by consecutive spawns, whereas it increased with time spent in production. Nauplii length and survival to zoea and mysis stages decreased with time spent in production, whereas no consistent influence of consecutive spawning was observed. Survival to PL2, and to the ammonia and salinity stress tests did not decrease with increasing time in production or spawning order. This study separated the specific influence of time spent in production (which negatively affects larval quality) and consecutive spawns (which had no effect or had an inconsistent effect), and reinforced previous suggestions that selection of females with multiple spawn capacity would be desirable for production purposes.     

Red Porgy,Pagrus pagrus,Larvae Performance and Nutritional Condition in Response to Different Weaning Regimes

Red porgy, Pagrus pagrus, is a candidate species for aquaculture diversification. The aim of this work was to assess whether an early supply of enriched Artemia (D1) or a direct step to dry diets (D3) would be advantageous weaning strategies for red porgy larvae, compared to a later supply of Artemia followed by dry diets (D2). Direct weaning to dry diet resulted in significantly lower growth, survival, pancreatic (trypsin and lipase), and intestinal (alkaline phosphatase) enzyme‐specific activity, with the exception of leucine‐alanine peptidase. The direct weaning strategy presented severe nutritional restrictions from early weaning stages with an associated delay of the maturation of digestive system. The two‐step strategy presented in D1 and D2 resulted in comparable results in most parameters, including survival. Weaning using enriched Artemia as an intermediate step is confirmed as the most adequate strategy for red porgy larvae. Digestive enzymes and selected fatty acids correlated well with performance responses to dietary regimes, thereby supporting the use of these parameters as sensitive and reliable indicators of red porgy nutritional or physiological status during larval stages.     

Evaluation of two probiotics used during farm production of white shrimp Litopenaeus vannamei (Crustacea: Decapoda)

This study examined the effects of Bacillus licheniformis strain CIGBC‐232, isolated from the gut of shrimp Litopenaeus vannamei and having antagonistic activity against Vibrio harveyi, on the immunity and larval quality of L. vannamei at various ontogenetic stages, in two separate experiments: (1) PL2 to PL17 exposed to the strain CIGBC‐232 under laboratory conditions (2) zoea I to PL8 exposed to the strain CIGBC‐232 and EPICIN 3W probiotics under farming conditions. The first experiment showed that phenoloxidase, peroxidase and superoxide dismutase activities were improved in animals grown with CIGBC‐232 compared to the untreated control. In tests, the resistance to osmotic stress was also enhanced. During the second experiment, animals treated with CIGBC‐232 exhibited significant (P < 0.05) increases in phenoloxidase activity (30–40% higher in zoea I–II, mysis II–III and PL 2–7) and in the respiratory burst (30% higher from PL 2 to 7) as compared to those animals that received EPICIN 3W. There was no significant difference in the lectins and agglutinins (except in PL1, 6 and 7), in peroxidase and superoxide dismutase activities, in the resistance to osmotic stress, nor in the survival rate among treatments. CIGBC‐232 treatment was able to reduce, the level of presumptive Vibrio spp. with respect to EPICIN 3W treatment in the tank water as well as in animals. At the end of both experiments, the growth of shrimp, i.e. weight and length was increased by CIGBC‐232 treatment. This study showed the probiotic effect of CIGBC‐232, which appeared to have a better probiotic performance than EPICIN 3W treatment.     

Differences in larval growth among families of Penaeus stylirostris Stimpson and P. vannamei Boone

Abstract. Full-sib families of Penaeus stylirostris Stimpson and Penaeus vannamei Boone were grown under controlled conditions in five experiments. Total length of shrimp larvae was measured at the following substages: protozoea one, mysis one and postlarva one. Analysis of variance showed that families differed significantly in size in all experiments at all substages tested. The average size possessed by a group of larvae early in development was significantly correlated with the size obtained in the later stages in P. siylirosiris , but not in P. vannamei . The component of variance in size due to family differences was determined and used to estimate heritabilities of size at the three larval substages in both species. Estimated heritabilities were higher for P. stylirostris than P. vannamei . In P. vannamei . the hcritability of size is greater for the protozoea and postlarval stages than the mysis stage.     

The Influence of Artemia and Algal Supplements during the Nursery Phase of Rearing Pacific White Shrimp, Litopenaeus vannamei

A 21‐d nursery trial was conducted to evaluate various food supplements on growth and survival of postlarval (PL) Litopenaeus vannamei. Each of four treatments was provided with an equal quantity of a dried commercial feed throughout the study. Three treatments received algae paste (Thalassiosira weissflogii) supplemented every 3 d. These include F, commercial feed plus algae; FAr3, commercial feed plus algae plus Artemia every other day during the first 7 d; and FAr7, commercial feed plus algae plus Artemia every day during the first 7 d. The fourth treatment served as control (FNA); it relied only on the commercial feed plus naturally occurring algae. At the conclusion of the nursery period, there were no significant differences in survival or feed conversion ration for PL nursed in the various treatments. Artemia did have some effect in that PL receiving Artemia supplement for 3 d (FAr3) were significantly larger than those that did not. Algal paste in itself had no significant effect. Overall, results suggest an advantage to supplementing dried feed with Artemia for at least 3 d during the first week of nursery culture but little advantage to the use of a diatom paste as a food supplement.     

Comparison of growth and survival of white shrimp postlarvae (Litopenaeus vannamei) fed dried Artemia biomass versus four commercial feeds and three crustacean meals

The use of dried Artemia biomass meal as an exclusive feed for postlarval white shrimp (Litopenaeus vannamei) was compared with four commercial feeds and three crustacean meals in a series of trials. Postlarvae (PL1–PL6) were stocked at a density of 1.5–2.5/litres in 16 tanks (100 litres volume) and fed, ad libidum, five times a day, over 23–29 days. Feeding postlarval shrimp with dried Artemia biomass resulted in a significantly larger size than feeding with three of the commercial feeds, and the crustacean meals. There was no significant size difference observed in animals fed with Artemia biomass and the commercial 'Golden Pearls' feed for postlarvae, however the coefficient of variation among the size of the 'Golden Pearls' fed animals was significantly higher. The weight increase of animals fed with Artemia biomass was higher than in animals fed with all the tested feeds. The survival rate was not significantly different in animals fed with Artemia flakes from 'Salt Creek', 'Bio-Marine', 'Golden Pearls' and Artemia biomass, however the survival rate was significantly larger in animals fed with Artemia biomass than in animals fed with the crustacean meals and 'Artemac.' Results suggest that dried Artemia biomass is a well-suited feed for postlarval L. vannamei.     

Selectivity of particle size by the shrimp Litopenaeus vannamei (Boone, 1931) larvae

Because of the filter‐feeding behavior of shrimp larvae, it is important to define precisely the size of the particle ingested in the different stages until postlarval stage where raptorial habits are more evident than the filter‐feeding lifestyle. Selectivity assays were conducted by using Polystyrene DVB particles with diameter between 1 and 50 μm as food. A group of organisms from each stage were put into the particle suspension for 15 min to let the polystyrene particles be ingested. The particle distribution in the media and the content of the gut of the larvae were characterized with digital image processing analysis. The results were compared using Ivlev selectivity formula, which compares the frequency distribution of each size of the particle in the media and in the gut of larvae. The results of selectivity were adjusted with a third‐order polynomial regression to determine the optimum and preferred size of the food particles for each larval stage between Zoea I and Postlarva I. It is concluded that the different larval stages of Litopenaeus vannamei may be considered as a single group of larvae who ingest foods with size between 5.71 and 20.33 μm. The optimal size of the food ingested was 14.42 μm wide.     

Use of Cyclop-eeze as a substitute for Artemia nauplii in larval rearing of giant freshwater prawn Macrobrachium rosenbergii (De Man 1879)

Four feeding experiments, replacing 25% (T₁), 50% (T₂), 75% (T₃) and 100% (T₄), by dry weight, of the live feed Artemia nauplii for Cyclop‐eeze, a new larval feed that was claimed to contain the highest known levels of astaxanthin and omega‐3 polyunsaturated fatty acids, were compared against a control that was fed with Artemia and egg custard alone, to the larvae of giant freshwater prawn Macrobrachium rosenbergii (De Man 1879). Analysis of different production characteristics of the larvae revealed that the highest survival up to postlarvae (PL) stage was obtained for T₂ in which 50% of the Artemia nauplii were replaced by Cyclop‐eeze [freeze‐dried (FD) deep frozen (DF)], and the highest astaxanthin content of the larval tissue obtained in T₄ in which the larvae were fed 100% Cyclop‐eeze, although the survival rate was the lowest in this treatment. The costs of different treatments were also compared. The Artemia consumption million⁻¹ larvae was the highest in control (11490 g), followed by T₁ (8240 g), T₂ (4990 g), T₃ (3730 g) and T₄, which completely replaced Artemia from stage 5 onwards (1830 g). The highest consumption of Cyclop‐eeze million⁻¹ larvae was in T₄ (1670 and 10 880 g), followed by T₃ (850 and 5560 g), T₂ (410 and 2690 g) and T₁ (230 and 1490 g) of FD and DF, respectively. The astaxanthin contents of the late‐stage larvae fed under the four treatments were 24.90, 27.40, 28.60 and 35.60 μg g⁻¹ tissue for T₁, T₂, T₃ and T₄, respectively, while that of the control was 23.70 μg g⁻¹. The lowest cost of live feeds million⁻¹ PL was obtained for T₂ (US$ 428.60), followed by T₁ (US$ 490.46), control (US$ 529.07) and T₃ (US$ 583.26), while it was the highest for T₄ (US$ 890.93). The results indicated that Cyclop‐eeze could economically replace Artemia nauplii at 50% level that could significantly improve the survival and carotenoid composition of the larvae of M. rosenbergii.