Chemical Studies on Larval Settlement and Metamorphosis of the Abalone Haliotis spp.

本研究初步阐明了鲍鱼幼虫沉降和变态的天然诱导剂，但由于鲍鱼的孵化季节有限，对与鲍鱼孵化季节不同的亚热带腹足动物Trochus niloticus也进行了试验。经过多次试验，我们最终建立了用于此目的的生物测定方法如下：1)将样品溶液（约5-300 μ l）加入平底玻璃试管（phi2.5 x 15cm）中。2)溶剂蒸发后，加入含有硫酸链霉素和青霉素G钾各150 mg/l的高压灭菌海水35 ml。3)引进约10只幼虫，1 ~ 8 d后进行显微镜观察。首先，我们对珊瑚红藻（Lithophyllum okamurae）的γ -氨基丁酸（GABA）和甲醇（MeOH）提取物对顶壳T.niloticus的变态作用进行了测试。本研究首次对niloticus幼虫变态进行了化学研究。在相当于5-15毫克风干藻类提取物的剂量下，藻类提取物诱导了更多的幼虫变态（约80%）。在10^<-5—3>M时，GABA也能诱导变形。两者的作用方式明显不同[Nippon swiss Gakkaishi， 59, 1261(1993)]。藻类活性原理被发现比多不饱和脂肪酸在更少的极性组分中被洗脱，其中一些已被报道能诱导一些盘虫和一些管虫幼虫的变态。频繁的台风袭击给获得试验用的幼虫带来了麻烦，导致活性原理的隔离不完全。发现海藻提取物中极性较低的组分可诱导褐螺旋体和褐螺旋体的变态。由于生物测定的数量有限，活性成分的分离尚未完成，要等到下一季才能完成。GABA首次被证实能使黄颡鱼和黄颡鱼的幼虫发生变态，但对黄颡鱼无明显的变态作用。我们中的一个人（Akutsu）已经获得了GABA在鲍鱼育苗生产中的成功应用的实验结果。少

This study has begun to clarify the natural inducers for larval settlement and metamorphosis of the abalone Haliotis spp. However, because of the limited hatching season for the abalone, the subtropical gastropod Trochus niloticus, whose hatching season is different from that of Haliotis spp., was also tested. After many trials we finally established a bioassay for this purpose as follows : 1) Sample solution (about 5-300 mul) was added into a flat bottom glass test tube(phi2.5 x 15cm). 2) After evaporating the solvent was added 35 ml of autoclaved sea water containing 150 mg/l each of streptomycin sulfate and penicillin G potassium. 3) About ten larvae were introduced and each larvae was microscopically observed after 1-8 days.First we tested gamma-Aminobutyric acid (GABA) and MeOH extract of the coralline red alga Lithophyllum okamurae for metamorphosis of the top shell T.niloticus. This study was the first chemical study on larval metamorphosis of T.niloticus. The algal extract indu … More ced larval metamorphosis (about 80%) at doses of the extracts equivalent to 5-15 mg of the air-dried alga. GABA also induced the metamorphosis at 10^<-5--3>M.The mode of action was clearly different from each other [Nippon Suisan Gakkaishi, 59, 1261 (1993)]. The algal active principle was found to be eluted in less polar fractions than polyunsaturated fatty acids, some of which have been reported to induce metamorphosis of some Haliotis and some tube worm larvae. Frequent typhoon attacks caused troubles in obtaining the larvae for the test, resulting in incompletion of the isolation of the active principle(s).The less polar fractions from the algal extract was found to induce the metamorphosis of H.discus and H.sieboldi. Because of limited numbers of bioassay, isolation of the active principle(s) has not been finished and is to be waited till next season.GABA was, for the first time, shown to metamorphose the larvae of H.discus and H.sieboldi, although no effect on H.diversicolor aqutilis. One of us(Akutsu) has got experimental results for a successful application of GABA to seedling production of the abalones. Less