Free-living nematodes have potential to be used as live food for early life stages of several species in marine aquaculture. Panagrolaimus sp. displays several favourable characteristics for this application. The present study proved the feasibility of propagation in monoxenic liquid culture on Saccharomyces cerevisiae. The development of yeast cell density, nematode numbers and size distribution was assessed daily for 15 days. After a lag phase of 4 days the inoculated first-stage juveniles started development to adults. Yields in terms of nematode number as well as biomass were highly variable. The maximum number of nematodes varied from 45 000 to 238 000 ml−1 and maximum biomass from 49 to 143 g l−1. Information on size, dry and wet weight of the nematodes is provided. The size spectrum of Panagrolaimus sp. individuals ranged from 176 × 8 μm to 1377 × 61 μm and 8.15 to 3202.39 ng wet weight. Water content of the nematodes was 71.7 ± 2.5%, so dry weight per individual was 2.31-905.95 ng. Differentiation of juvenile stages by body length was not possible. Based on comparison of dry weight per individual the Panagrolaimus sp. might be used as a substitute for rotifers, a commonly used live food organism.
Panagrolaimus sp. strain NFS-24-5 has potential to be used as live food for early stages of fish and crustacean species in marine aquaculture. One constraint to its commercialisation is the lack of a method that enables storage of nematodes over a longer time span. The objective of this study was to develop a procedure to transfer nematodes into a dormant state by desiccation. The nematodes were concentrated at densities of 25, 50, 100 and 200 x lO'' individials cm~^ on nylon net or cellulose paper, preconditioned for 72 h at 97.3% relative humidity (RH) and then stored at 52.9 or 32.8% RH for 1 week. Cellulose was a better carrier for the nematodes. Survival of the nematodes was reduced only at the highest nematode density on both materials. The water activity of desiccated nematodes was 0.44 and 0.33 at 52.9% and 32.8% RH, respectively, well beyond a point to prevent microbial growth. After storage over a period of 10 weeks at 25 x lO-* nematodes cm~^ at 52.9 and 32.8% RH, 92% of the nematodes were still alive. Monitoring the size distribution revealed no changes at 52.9%; RH, but there were more of the larger nematodes dying at 32.8% RH in two out of three experiments. The method can be used to store quiescent Panagrolaimus sp. (strain NFS-24-5) for transportation and use in small scale feeding experiments for marine fish and crustacean larvae.
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