| The seven band grouper (Epinephelus septemfasciatus) belongs to thelarge grouper, which was popular in china because of fast growth, lowtemperature tolerance, power adaptability, abundant nutrition and deliciousflesh, etc; and with high economic value and market potentiality. This studyobserved morphological character of egg and the fertilization process withscanning electron microscopy, described the process of embryonicdevelopment as well as changes of the larvae、juveniles and young fish withmicroscope. We studied the initial baits of larva in grouper breedingprograms, as well as the larvae physical hunger, malnutrition, growth lagand other issues caused by the initial baits of larva. Then comparedadaptability to the gruadual and sudden temperature changes of the juvenileseven band grouper with those of kelp bass (Epinephelus moara),red-spotted grouper (Epinephelus akaara), which would provide referencefor scale artificial culture of Epinephelus akaara. The main results were asfollows:Microscopy and scanning electron microscopy were used to observethe frozen and fresh sperm motility of seven band grouper (E. septemfasciatus), morphological character of egg and sperm penetration.The results showed that: there was no significant difference in the spermmotility and fertilization rate between the frozen and fresh sperm, theywere the same in the artificial culture success rate and larval cultivation ofE. septemfasciatus. Egg fertilization hole was expanding vibrioid-shapedmicropyles. Fertilization process of E. septemfasciatus was rapid，spermpenetration could be observed at about30seconds, the tail was left outsidethe fertilization hole. After sperm penetration, fertilization cone formed inthe fertilization hole, around which flocculent fertilization stopper appeared,fertilization hole closed. There was only one sperm observed intomicropyle of fertilized egg, no more than one sperm were observed into asame egg.The embryonic development, morphological development of larva,juvenile and young fish of kelp bass Epinephelus septemfasciatus wereobserved and studied. The morphological features and the developmentaltime were described in great detail from fertilization to young fish. Theresults shown that the time for the embryonic development is40h48min inthe water with temperature (20±1)℃, salinity30±0.5, DO7.5mg\L, pH7.96.Based on the obtained data, six periods including28stages ofEpinephelus septemfasciatus embryo are established, which are cleavageperiod, blastula period, gastrula period, neurula period, organogenesis period and hatching period.After5days rearing in the sea water oftemperature (20±1)℃, salinity30±0.5, DO≥5mg／L, pH8.0±0.5, theyolk-sac of larvae would disappear and changed into late larva; after30days, the fast growing larvae among the others developed into juveniles;after68days, the fast growing juveniles among the others completedmetamorphosis and changed into young fish. In addition to the gonads isnot yet mature, external morphology, habits and adult non-discriminatory.Depending on the source of nutrition, the growth stages of the larvae can bedivided into: the endogenous vegetative stage (yolk, oil balls)-Mixedvegetative stage (yolk, oil balls, bait)-exogenous vegetative stage (bait).Using artificial breeding of Seven band grouper larvae hatching, underthe conditions of the water temperature of23-24°C, salinity29±1, pH8.0-8.5, through the hunger experimental, under starvation stressresearching seven band grouper larvae feeding, growth, development andsurvival variation. The results showed: the endogenous nutrition period, thegrowth performance there is no significant difference between the controlgroups and hunger groups, similar to the yolk sac and oil globule utilization,growth rate is significantly higher than the follow-up periods. Mixotrophicperiod, in the case of lack of outside nutrition, the larvae feeding rate,growth rate, and survival rate will decline rapidly. When the hunger groupown energy is depleted, coming a weak negative growth. To irreversible point period, the negative growth were intensified until the death of100%.The entire development process of the hunger groups larvae averagegrowth rate was48.8%of the normal feeding larvae. Seven-band grouperlarvae’s PNR period was only2-3days, and the resistance to starvationsurvival index was38.78%.Under the starvation conditions, the survivalrate of larvae with the hatching days relationship: y=-1.1201x~2-3.682x+111.99(R~2=0.9525), removal of the first day of the newly hatched larvae,the relationship of the entire growth process, the total length with thehatching days relationship: y=-0.0186x~2+0.1408x+2.2326(R~2=0.8769).Normal feeding group larval growth mode: the endogenousnutrition-mixed nutrition-exogenous nutrition; hunger group growthmode: endogenous nutrition-stationary growth phase-weak negativegrowth phase-PNR period.Two weaning food Rotifers and oyster eggs were used to analyze andcompare the effect on the post-larval of seven-band grouper, with threedifferent feeding modes (A rotifers, B oyster eggs, C mixture of oyster eggsand rotifers) under artificial rearing condition. Through observation aboutthe feeding situation of5day-old larvae and larvae gastrointestinal fullnessof4day-old to20day-old larvae to discussed the larval feeding habits andthe relationship of light and feeding. The results showed that feeding withoyster eggs for3days had more distinct promoting effect than group A fed with rotifers directly, the specific growth rate of total length of group B is4.969%, were2.5and2.4times of A and C, respectively. Before the10days of old, Group B in total length, anal distance and mouth width aregreater than the other two groups; Two obvious feeding peak periods are in9:00~10:00and13:00~14:00of5day-old larvae. The light intensity isbetween720~1018lx and865~923lx respectively. The satiation rate of4-day-old larval fish is lower, only40%reach three levels in food intake.4to10-day-old larvae satiation rate fluctuate, after10-day-old began to rise,and after13-day-old reach the100%basically. |
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