Development of indoor grow‐out practices for polychaete, Marphysa gravelyi with a note on biochemical composition

Abstract

Polychaetes are multi-segmented worms, being exploited from the backwaters for shrimp hatcheries to be used as a maturation diet for shrimp broodstocks. Non-selective collection of polychaete worms poses a severe hazard to the ecosystem; hence, a grow-out system was developed for Marphysa gravelyi. Adult, M. gravelyi of 17 ± 0.4 cm length (n = 40) when reared in 100 L tanks, produced 1800 numbers of juveniles having an average length of 7 ± 0.2 cm with 80% survival in 4 months. The juveniles (7 ± 0.2 cm (n = 50) worms were reared again in 25 L tubs from which 45 adults (20 ± 0.3 cm) could be produced in 4 months with 90% survival. Juvenile, M. gravelyi (n = 500) when mass-reared in 1000 L FRP tanks by feeding Skeletonema costatum (106​ CFU/ml), produced 400 adults (20 ± 0.2 cm) as biomass with 80% survival in 4 months. The nutrient profile of adult M. gravelyi revealed protein, carbohydrate and lipid to be 33, 14 and 40 g % respectively. Crude M. gravelyi extract showed the highest bacterial inhibition on Staphylococcus aureus (18 ± 0.3 mm) and lowest on Bacillus subtilis (14 ± 0.2 mm). The present study revealed that growing polychaete worms in a controlled condition is advantageous, compared to collection of polychaete worms from wild which might seriously deplete their natural stocks, and cause physical disturbance of soil exposing heavy metals with the release of ammonia, and phosphorus compounds leading to eutrophication.