EMBRYONIC AND PRE2LARVAL DEVELOPMENT OF TR ID EN TIGERTR IGONOCEPHALUS AND ADAPTABIL ITY TO SAL INITY

Tridentiger trigonocephalus widely exists in coast of the Pacific Ocean.There are very few reports about the character of their early life.Fish was sensitive to the change of environmental factors in the early life.So embryo and larva can indicate the environmental change.Salinity is one of the most important ecological factors in the embryonic and prelarval development of T.trigonocephalus.The construction of the Three Gorges Project on the mainstream may act on the environment not only in the reservoir, the middle and low reaches of the river, but also in the estuary. It is necessary to study the relationship between salinity and fish early life.By observing the morphological character of embryonic and prelarval development ofT.trigonocephalus with Nikon microscope, the total development time of every development stage was noted and calculated1The characteristic imageswere taken byNikon camera1The characters of early life stages and effects of salinity on the early development ofT.trigonocephaluswere studied1The experimentation group s included salinities of 0, 2, 4, 6, 8 and 10, respectively1Every group was put into 100 oosperm or 10 p re2larva under the water of temperature(1810±015℃), deliquescent oxygen 616-812 mg/L, pH712-718.The results showed fecundation rate and hatching rate were the highest at salinities of 4 and 6.Fecundation rate was(76128±2173)% and(74163±5149)%, and hatching rate was(66195±2199)% and(62115±2118)%, respectively1Hatching time was the shortest and embryonic development was the most quickly at salinities of 4 and 6.Hatching time was 22818±519h and 22115±512h, respectively. It spent longer time from heart beating stage to hatching stage, 56 percent of the total time.Meanwhile, pectoral fin, swimbladder, kidney and bladder came into being before prestage of hatching stage.The deformity rateswere from 5% to 20% at salinities of 8 and 10 and the other salinitieswere lower.The larva was(21534±01078)mm in body length.The long and short diameter of yolk sac were(01421±01047)mm and(01369±01038)mm, respectively.The yolksac disappeared and organs begin to form after five days.The organ development of larval T.trigonocephalus was more quickly at salinities of 4 and 6 than the others.The range of survival activity index was from 41183 to 46183 and prelarva vigor was high with water salinity from 0 to 6.The range of survival activity index was from 23143 to 29113 and prelarva vigorwas low at salinity of 8 and 10.At low salinity range, the suitable salinity for hatchingwas from salinity 4 to 6 and for prelarvae survival and growth was from salinity of 2 to 4, respectively.