ノコギリガザミの卵およびふ化幼生のハリフトロス症に対するホルマリン浴の効果

Abstract

In 1987, a fungus disease caused by Haliphthoros sp. occurred in the ova and larvae of the mangrove crab Scylla serrata cultured at Yaeyama Station of Japan Sea-Farming Association, Okinawa, and experiments on the effect of formalin bath on this disease were made. The bath treatment with 25 ppm formalin in a hatching tank inhibited the occurrence of the infection in newly hatched zoeae from ovigerous females with infected eggs on the surface of the egg-mass. Although a 2-day-bath with 75 ppm formalin could not kill the fungus within the eggs, a 2-hour-bath with 20 ppm formalin was effective to inactivate the zoospores released from infected eggs. Newly hatched zoeae, on the other hand, were tolerant of exposure to 20 ppm formalin. This suggests that the occurrence of the disease can be controlled by a bath treatment with 25 ppm formalin in a hatching tank, even if the eggs are obtained from ovigerous females with infected eggs.