A comparative study on the nutritional value of three Polychaete species used in Shrimp Aquaculture

Resumo

The potential use of polychaete worms are as a dietary source of protein, lipid, amino acids, and vitamins for aquaculture species and also used as alternative feeds of fish meal and fish oils. Many recent studies have been documented the nutritional benefits of polychaetes for aquaculture species, for their satisfactory food intake and reproductive performance in brood stock. Most of the polychaetes were used in hatcheries are wild caught. The commercial harvesting of polychaetes may leads to the disturbance in the benthic community and the ecosystem and also may leads to the depleting population in the ecosystem. Further the development of polychaete culture is therefore of economic importance beyond that the associated bait supply industry which is acted as the initial catalyst for this development.
Hence, the present study has been made with three different polychaete species, to assess the nutritional value of the three species, one was imported (Nereis virens) and two locally available species (Perenereis cultrifera and Glycera sp) for commercial uses in the shrimp aquaculture industry. The samples were collected from mandapam and Palk Bay Area and these samples were oven-dried and powdered. All the samples were analyzed and calculated in dry weight per 100 grams of sample. Moisture content was calculated by loss of drying (LOD) method.
Protein and amino acids were estimated by Appendix IV (British Pharmacopeia 2007), and detailed amino acid profile was assessed by HPLC. Carbohydrates were determined by gravimetry method from Appendix IV in Volume 3 Indian Pharmacopeia (2007). Total fatty acid and fatty acid profile were estimated through gas chromatography based on British Pharmacopeia (2007). Minerals were analyzed by flame photometry and atomic spectrometry (Indian Pharmacopeia, 2007; US pharmacopeia by Lawrence Evans, USP 29 NF 22 vol. 28).
Vitamins were determined by assay method using liquid chromatography in US pharmacopeia (Lawrence Evans, USP 29 NF 22 vol. 28). Ash content was estimated in a tared silica crucible at a temperature of 400 to 500º C in a muffle furnace. Fibers was estimated by an enzymatic– gravimetric method followed by AOAC method 985.29 (1990). In the present study, among the
three polychaete species, the maximum moisture content was recorded in Perinereis cultrifera (5.60 g) followed by Glycera sp (5.34 g) and Nereis virens (3.89 g) and the maximum value of protein content was recorded in P. cultrifera (53.62 g) followed by Glycera sp (50.50 g) and N. virens (49.04 g). The maximum total fatty acid content was recorded in N. virens (32.31 g) followed by Glycera sp (20.99 g) and P. cultrifera (11.99 g). The result of major fatty acids profile, showed that the Saturated Fatty Acid (SFA) content was higher when it compare to PUFA and MUFA in all three polychaetes .The maximum ash content was recorded in Glycera sp (20.32 g) followed by N. virens (11.73 g) and P. cultrifera (10.91 g) and the maximum carbohydrate content was recorded in P. cultrifera (17.53 g) followed by N. virens (2.67 g) and Glycera sp (2.04 g). In this study, EAA was recorded higher content when it compared to NEAA in all the three species of polychaete. In the EAA the most dominant amino acids are lysine,
arginine, and isoleucine and in the NEAA are cysteine, alanine, asparagine, and aspartic acid whereas the lesser EAA and NEAA are methionine and serine, respectively. In vitamin study, P. cultrifera, N. virens and Glycera sp showed higher content of vitamins A, B1, and E and less in vitamin C. Mineral content was dominant with chloride of all the three species of polychaete.