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preliminary evaluation of the potential of b. plicatilis for use as a live food for freshwater prawn larvae

Research Article ºÚÁÏÍø
Shivananda Murthy H1, Yogeeshababu MC1 and Tejpal CS2*
1Department of Aquaculture, Karnataka Veterinary, Animal and Fisheries Sciences University, College of Fisheries, Mangalore 575002, India
2National Fisheries Development Board, Department of Animal Husbandry, Dairying and Fisheries, Ministry of Agriculture, GOI, India
*Corresponding author: Tejpal CS
National Fisheries Development Board
Department of Animal Husbandry, Dairying and Fisheries
Ministry of Agriculture, GOI, India
E-mail: tejpal.arun@rediffmail.com
 
Received October 07, 2011; Published October 26, 2012
 
Citation: Shivananda Murthy H, Yogeeshababu MC, Tejpal CS. (2012) Preliminary Evaluation of the Potential of B. plicatilis for Use as a Live Food for Freshwater Prawn Larvae. 1:383. doi:10.4172/scientificreports.383
 
Copyright: © 2012 Shivananda Murthy H, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
 
Abstract
 
Artemia is predominantly used as a live feed in freshwater prawn hatcheries. In view of high cost of cysts and their occasional scarcity, the dependence on Artemia is a major concern in the expansion of Macrobrachium rosenbergii hatcheries. Efforts are made to replace Artemia by other live food organisms and inert feeds. In the present study, an attempt was made to evaluate rotifer, Brachionus plicatilis to replace Artemia either partially or fully in prawn larval rearing unit. The experiment was carried out in triplicate groups with four feed treatments. Prawn larvae were fed with Artemia alone (100%) T1 (A100), T2 Artemia (70%) and Brachionus plicatilis (30%) (A70 and B30), T3 Artemia and B. plicatilis, (50% each) (A50:B50) and T4 B. plicatilis alone (100%) (B100). Group T2 (A70 and B30) resulted in good survival, growth and mean larval stage (MLS) of prawn larvae, which was not significantly different from treatment T1 group fed with Artemia alone. The survival obtained in A50:B50 and B. plicatilis (B100) alone was not satisfactory, and differ significantly from the other treatments.
 
Keywords
 
Larval nutrition; Survival; Growth; Rotifer; Artemia nauplii; Brachionus plicatilis; Macrobrachium rosenbergii
 
Introduction
 
Artemia nauplii are the predominant live food used in shrimp and prawn hatcheries. Though supplementation of Artemia with prepared feed has been reported [1,2], no substitutes have yet become standard in freshwater prawn hatcheries. In view of high cost of cysts coupled with their occasional scarcity, the dependence on Artemia is a major concern in the sustainable seed production of M. rosenbergii in hatcheries. Further, the exuvia and capsules (outer calcareous layer of cysts) accumulate in the larval rearing tanks. Bacterial degradation of these materials fouls the water; accumulated debris entangles larvae and leads to increased larval mortalities. The cysts or shells which are ingested by the larvae cannot be digested and they may cause blockage of the gut or have other deleterious effects [3]. Although partial success has been achieved in the development of formulated feed to supplement and replace Artemia in prawn larval culture [1], the use of these diets has limited success in promoting sustained larval production [4]. In contrast, rotifer B. plicatilis has a short life cycle, can be cultured in high densities and has favourable nutritional contents [5]. Since it is small in size, it can be consumed completely by small decapods crustacean larvae. The individuals of M. rosenbergii in early larval stages (I to III) apparently graze on the appendages of Artemia but are not able to consume entire nauplii [6]. In contrast to this Brachionus plicatilis found to be good live diet for M. rosenbergii because early larval stages could consume entire rotifer simply due to its smaller size. In this direction, an attempt was made in this study to evaluate rotifer, B. plicatilis to replace Artemia either partially or fully in prawn hatcheries.
 
Materials and Methods
 
Experimental animal
 
One day old larvae of Macrobrachium rosenbergii were procured from the College of Fisheries hatchery, Mangalore, India and were used for the study.
 
Experimental design
 
18,000 one day old prawn larvae were randomly distributed into four groups. Four treatment groups namely, T1 (100% Artemia (A 100)); T 2 (70% Artemia and 30% B. plicatilis (A70: B30)); T3 (50% Artemia and 50% B. plicatilis (A50: B 50%)) and T4 (100% B. plicatilis alone (B100)) were arranged in triplicates following a Complete Randomized Design (CRD) design and fed respective diets. The total volume of water in each tank was maintained at 50 l throughout the experimental period. In all the treatments, larvae were fed with live food organisms twice a day at 8.30 hrs and 17.30 hrs at the rate of 3 organisms per ml of tank water and the number of Artemia and B. plicatilis varied according to the treatment. Round the clock aeration and water recirculation was provided.
 
Experimental diet
 
The study was conducted to evaluate the nutritive value of B. plicatilis (rotifer) and its effect in the feeding of M. rosenbergii by replacing Artemia. The experiment consisted of four dietary treatments in triplicate groups. The larvae fed with 100% Artemia (A 100) T1, 70% Artemia and 30% B. plicatilis (A 70: B 30) T2, 50% Artemia and 50% B. plicatilis (A 50: B 50%) T3 and 100% B. plicatilis alone (B 100) T4. B. plicatilis samples collected from nearby Nethravathy estuary were segregated and multiplied in the laboratory by providing chlorella and yeast as food. After 5-7 days of inoculation in nutrient rich media, B. plicatilis attained a peak density of 100-150 individuals/ml and were harvested with a scoop net (100-150 μ) early in the morning or late in the evening when they were at the surface. The harvested biomass of B. plicatilis was washed thoroughly and fed to the prawn larvae. Artemia cysts were decapsulated and hatched in the laboratory and fed to prawn larvae.
 
Proximate analysis
 
Experimental diets were analyzed using standard methods [7] for crude protein, lipid and ash. Crude protein by Kjeltec semi-automatic system (Tecator); lipid by Soxtec system (Model SD2, 1045, Tecator) and ash by muffle furnace incineration at 550°C for 6 h were analysed. The proximate composition of Artemia and rotifer were analyzed in triplicates.
 
Water analysis
 
Physico-chemical parameters of water was analysed at weekly intervals. Temperature of water was measured using mercury in glass thermometer having an accuracy of 0.1°C. The pH was measured using a laboratory lovibond comparator. Salinity of the water was estimated by refractometer with 1 ppt accuracy. Dissolved oxygen, free carbondioxide and total ammonia were determined following standard methods [8].
 
Mean larval stage (MLS) and relative percentage survival
 
Mean larval stage (MLS) and relative percentage survival were estimated every second, third and fourth day respectively for the first, second and third week onwards. Thirty randomly sampled larvae from each treatment were identified following the descriptions given by Uno and Kwon [9]; Murai and Andrews [10]. Development of the larvae was determined by calculating the mean larval stage (MLS) by the formula given by Lovett and Felder [6].
 
MLS = Σ(S x PS)
 
Where ‘S’is the larval stage number and PS is the proportion of the larvae at stage ‘S’.
 
The relative survival of larvae in each tank was estimated by taking random samples. One liter of water from each tank was taken ten times and average number is multiplied to whole volume. The experiment was terminated when more than 95% of the larvae metamorphosed to post-larvae. All the post larvae were harvested from each tank and counted to calculate the percentage survival. After termination of the experiment, 50 post larvae were randomly taken from each tank to measure individual total length (from tip of the rostrum to the end of the telson) and total weight.
 
Statistical analysis
 
The data were statistically analyzed by one way ANOVA and Duncan’s multiple range test by statistical package SPSS version 11 to determine the significant difference between the treatments comparisons were made at 5 % probability level [11,12].
 
Results
 
Water quality parameters analyzed during the course of study are given in the (Table 1). Water temperature, pH, dissolved oxygen and ammonia in different treatments varied from 24.3 to 26.7°C, 7-7.8, 5.3- 5.85 mg/ l and 0.03 to 0.07 mg/l respectively. Free carbon dioxide was not detectable in any of the experimental tanks.
 
Table 1: Water quality recorded in different experimental tanks (values are means three replicate groups in each treatment)
 
The survival rate of Macrobrachium rosenbergii larvae fed with T1 group (Artemia alone (A100%)) showed the highest survival (43.33%) followed by (42.22%) in the T2 group (A70:B30 (70% Artemia and 30% B. plicatilis)). Lowest survival was recorded in T4 group when larvae fed with (B. plicatilis (B100%)) alone (Table 2). However, there was no significant difference in the larval survival recorded between T1 and T2 treatment groups. Whereas, the survival rates obtained in T1 (A100) and T2 (A70:B30) were significantly different from the treatments T3 (A50:B50) and T4 (B100) groups.
 
Table 2: Post-larval production of M.rosenbergii in different feed treatments (values are means SD)
 
The mean larval stage (MLS) of Macrobrachium rosenbergii in different treatment groups are given in the (Table 3). The MLS showed significantly (p<0.05) higher among two treatment groups (T1 & T2). The development of the larvae is expressed as the mean larval stage (MLS). In the treatment T1 and T2 groups larvae took relatively less time to reach the next stage, where as in the T3 and T4 treatment groups larvae took more time to reach the next stage. The highest MLS value was recorded in the T1 followed by T2, T3 and T4. There was no significant difference in the MLS values of larvae fed with T1 (A100) and T2 (A70: B30). But, the other two treatments T3 (A50:B50) and T4 (B100) differed significantly from T1 and T2.
 
 
Table 3: Comparison of mean larval stages (MLS) of M. roesnbergii in different feed treatments (values are means and SD of 3 replicate groups).
 
The recorded length and weight of post-larvae fed with different diets was highest in T1 fed Artemia alone, than T2 followed by T3 and T4 ( Table 4). Data pertaining to the proximate composition of Artemia and Rotifer (B. plicatilis) is presented in table 5. Crude protein estimated in Artemia and rotifer were 48.43 ± 1.36 and 30.90 ± 1.0, respectively the fat content was 19.00 ± 0.26 and 5.99 ± 0.20 and ash was 7.43 ± 0.21 and 19.14 ± 0.67 respectively.
 
Table 4: Length and weight of post- larvae recorded under different feeding regimes (values are means of three replicate groups) (n = 6).
 
Discussion
 
In the present study, all the physico-chemical parameters of water namely temperature, pH, DO, CO2, total alkalinity and ammonianitrogen were found well within the optimum range of requirement for the growth of Macrobrachium rosenbergii larvae. The survival rate of Macrobrachium rosenbergii was significantly better in the T1 and T 2 groups when compared with T3 and T4 groups. Lovett and Felder [ 6] observed no significant difference in the survival of the larvae fed Artemia alone and combination of Artemia and B. plicatilis. The mean larval stages (MLS) of larvae fed with different diets vary significantly among the treatment group. MLS showed better values in the T1 and T 2 groups which were fed with Artemia and Artemia and B. plicatilis (70+30%) when compared with T3 and T4 groups fed with Artemia and B. plicatilis (50+50%) and B. plicatilis. Our finding of this study are comparable to results of Alam et al., [13] who reported that higher MLS values for larvae fed Artemia alone and combination of Artemia and Moina as compared to larvae fed Moina alone.
 
Prawn larvae fed Artemia alone showed better survival, MLS and growth and took shorter time to reach the next stage in the present study. This is attributed to high lipid content of Artemia than rotifers (Sulkin, 1975) [14] (Table 5) and presence of higher levels of n-3 HUFA’s [15]. Further, the caloric content of Artemia is better than rotifers (Emmerson, 1984). In the present study, as the percentage of Artemia in the feed decreased the survival of the larvae also reduced. However, survival and growth recorded by feeding T2 (A70:B30) was not significantly different from T1 (A100) treatment. The survival of larvae obtained by feeding T3 and T4 was not satisfactory because, 50% of rotifer or rotifer alone (100) was not sufficient to fulfill the nutritional requirement of prawn larvae. The rotifer, B. plicatilis found to contain less amount of n-3 HUFA’s and energy compared to Artemia [16].
 
Table 5: Proximate composition of Artemia and B. plicatilis (% dry weight).
 
The findings of the present study demonstrate that combination of Artemia and B. plicatilis in the ratio of A70:B30 respectively was found the best combination for larval rearing of M. rosenbergii in view of its cost effectiveness. Based on the results, it was possible to reduce 30% of cost on use of Artemia cysts. Rotifer, B. plicatilis could be raised in the laboratory without much involvement of cost and labour. Further research is needed in this direction to study the replacement of Artemia by rotifer and other zooplankton in the larval rearing of freshwater prawn.
 
Acknowledgments
 
The authors are grateful to the Indian Council of Agricultural Research, New Delhi for sanctioning research fund support under ICAR Cess funds, the work carried out forms part of the project work.
 
 
References