NH<sub>4</sub>OH による二枚貝の産卵誘発

Abstract

It has been reported that the discharge of sexual products of Pecten yessoensis, Haliotisdiscus, H. sieboldii, Anadara subcrenata and Brachidontes senhousia were artificially induced by simultaneous increase of temperature and alkalinity, but in Mytilus edulis, the mature sexual products were discharged by mere bathing its cut mantle in ammoniated sea water. The writer, in the present experiment which used NH4OH, was not only successful in obtaining the discharge of reproductive substanecs of Mactra venerifomis, M. sulcataria, Gryphaea gigas etc. but also of Tapes japonica and Meretrix lusoria which have not previously been induced to discharge artificially by the injection of k-salts or faradic stimulation. Results obtained are as follows: 1. Presumptively effetive factor on the spawning induction of Mactra. The first experiment using Mactra veneriformis and M. sulcataria was carried out to ascertain whether the induction of spawning was due to pH (alkalinity) or NH+4 ion. The sea water including both NH4OH (NH+4 ion and pH) and NH4Cl (NH+4 ion), was effective in producing the discharge of reproductive substances, while NaOH (pH)-sea water was not effective. From these results, it is difficult to decide whether pH or NH+; ion is more effective, but it is conceivable that NH+4 ion will be particularly effective in the discharge, as KCl solution is in the case of the mantle of Mytilus edulis (see Table 1). 2. The treatment with NH4OH-sea water. When Mactra veneriformis, M. sulcataria, Gryphaea gigas, Corbicula japonica and Trapezium japonicum, during their spawning season, were immersed in a suitable concentration of ammoniated sea water, they began to spawn their reproductive substances without the stimulation of temperature (see Table 2). 3. The injection method of NH4OH solution. Meretrix lusoria and Tapes japonica could not spawn with the treatment in NH4OH-sea water, but successfully spawned when 2cc of suitable concentration of NH4OH solution were injected directly into the gonad(see Table 3). As the ova and spermatozoa discharged by the methods above-mentioned were all mature, the author was successful in the artificial fertilization with ease and fertilized eggs developed normally to swimming larvae.