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Mass production of the resting eggs of the marine rotifers Brachionus plicatilis (formerly called L-type) and B. rotundiformis (called S-type) were achieved using a batch culture method [reviewed by Hagiwara, A., 1994. Practical use of rotifer cysts. The Israeli Journal of Aquaculture — Bamidgeh 46, 13–21]. This paper summarizes the further advancements achieved over the last three years. The efficiency of resting egg production can be improved by employing semi-continuous culture method. Some semi-continuous cultures collapsed between the 15–20th days due to bacterial effects. However, the rotifer culture was stabilized by placing filtration mats to remove organic material. Thus harvests of 8.1 × 10 2 resting eggs/day/g (dry weight) Nannochloropsis oculata were achieved, which is 3.0 times more efficient than that from batch cultures. Resting eggs of B. rotundiformis , however, were not mass produced after the exchange of culture water. Resting eggs can be stored in sea water for more than 20 years at 5 °C under complete darkness. Hatch rates of the eggs, however, decreased when stored with abundant organic matter. Resting eggs could be canned under an atmospheric pressure of 48–61 kPa after lyophilization (− 30 °C) without reducing their hatch rates.

Scanning electron microscopy indicated that stored resting eggs of the marine rotifer Brachionus plicatilis Muller were colonized by numerous bacterial cells that affect the hatchability of resting eggs. The effectiveness of chemical disinfectants on the hatching of the resting eggs was studied using selected chemicals and antibacterial drags. The hatching success rate of the fresh and stored eggs was 26 ± 5.8% and 0%, respectively. Sodium hypochlorite (1.0 p.p.m.) increased the hatching rate to 48 ± 1.3% in freshly-collected and 28 ± 1.8% in stored eggs. Physical disintegration of the bacterial mat occurred after 1 h of treatment with sodium hypochlorite. Among antibacterial drugs, sodium nifurstyrenate (Erubaju) enhanced the hatching success rate to 40 ± 1.2% and 20 ± 1.1% for the freshly-collected eggs and stored resting eggs, respectively. However, tetracycline and oxytetracycline did not significantly influence the hatching of the stored eggs. These observations are discussed in relation to the development of an improved method for the processing and hatching of rotifer resting eggs.

Recent research has indicated that the hatchability of mass-produced rotifer (Brachionus plicatilis) resting eggs (stored in sea water in the dark at 4°C) gradually decreases due to bacterial infection of the porous egg surface. We investigated whether lyophilization as well as a canning treatment could solve the problem of bacterial infection of resting eggs. The canning method preserves eggs in a dry form, after lyophilization at −40°C. The resting eggs were packed in cans under various pressures: 21, 34, 48, 61, 75, 88 and 101 kPa. The viability of the canned resting eggs was tested by hatching experiments done 6 and 12 months after canning and storage at 5°C. When partial pressures were less than 88 kPa, percent hatching after 6 months ranged between 16 and 20%, similar to that of uncanned eggs (19% hatching), but significantly lower (9 and 11%, P