脉红螺附着变态与食性转换的研究

Studies on larval metamorphosis and feed conversion of Rapana venosa

为实现脉红螺苗种的规模化生产,本实验通过对脉红螺幼虫培育、采苗、稚螺培育等方面的系统研究,探索了脉红螺苗种繁育过程中幼虫附着变态率低和饵料转换难的问题。结果显示：脉红螺浮游幼虫前期（0-12 d）生长较快,壳高平均日增长21.8μm;中期（13-18 d）生长较慢,壳高平均日增长3μm;后期（19-30 d）生长加快,壳高平均日增长46.8μm。用取自沉淀池中的新鲜海水对脉红螺浮游幼虫进行附着变态诱导,诱导第1天脉红螺浮游幼虫开始出现附着变态,第4天时,附着变态活动基本结束,附着变态率为40%。为变态后的稚螺投喂刚附着的长牡蛎和魁蚶稚贝,第1-8天,稚螺壳高平均日增长65.6μm;第9天开始,稚螺生长速度加快;第9-12天,稚螺壳高平均日增长136.4μm;第13-16天,稚螺壳高平均日增长307.3μm;第17-20天,稚螺壳高平均日增长445.8μm。研究表明,用取自沉淀池中的新鲜海水诱导脉红螺浮游幼虫的附着变态效果好,刚附着的长牡蛎稚贝和魁蚶稚贝可以作为脉红螺稚螺培育阶段的适宜饵料。

In the past decades,the natural resources of Rapana venosa in China have obviously declined because of over-exploitation and habitat destruction.It is very necessary to study the artificial reproduction of R.venosa for recovering natural resources and meeting the demand of the market.However,large-scale artificial seedling of R.venosa is still hampered by low larval metamorphosis rates and feed conversion.In order to solve these problems,larval rearing,spat collection and juveniles＇ culture were systematically investigated in the study.The results showed that in the early stage of the planktonic larvae,growth rate of shell height was 21.8 um/d（0-12 d）.In the middle stage of the planktonic larvae,growth rate of shell height was 3 urn/d（13-18 d）.In the late stage of the planktonic larvae,growth rate of shell height was 46.8μm/d（19-30 d）.After being induced by the fresh seawater from the precipitation pond,the planktonic larvae began to settle and metamorphose on the first day and the process of settlement and metamorphosis ended with 40%of larval metamorphosis on the fourth day.The juveniles of R.venosa can feed on spats of Crassostrea gigas newly settled to the scallop shells and spats of Scapharca broughtonii newly settled to the monofilament nylon.Growth rate of shell height in the juveniles was65.6μm/d（1-8 d）.From the ninth day,growth rates of the juveniles obviously quickened.Growth rates of shell height were 136.4μm/d（9-12 d）,307.3μm/d（13-16 d） and 445.8μm/d（17-20 d）,respectively.It is suggested that the competent larvae of R.venosa can be induced to settle and metamorphose by the fresh seawater from the precipitation pond.Spats of C.gigas and S.broughtonii could be animal feeds of the juveniles of R.venosa.