Mass production and preservation of the resting eggs of the euryhaline rotifer Brachionus plicatilis and B-rotundiformis

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 x 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. rotundtformis, 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 degrees 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 degrees C) without reducing their hatch rates. (C) 1997 Elsevier Science B.V.