Effects Of Different Ecological Conditons On Gonad Development Of Litopenaeus Vannamei Broodstock

In the cultivation of Litopenaeus vannemei, seedling quality is a key factor which depends on the quality of broodstock. Different factors have different effects on cultivation of broodstock, a better cultivation can be reached if the broodstock is cultivated under suitable conditions. This dissertation studies the effects of different temperature, salinitie, light intensitie and natural diets on gonad development of Litopenaeus vannemei. This dissertation also studies the effects of Oocystis borgei and Bacillus subalis on water quality improvement and gonad development of Litopenaeus vannemei, the study provide bases in looking for the optimum ecological conditions in cultivation of Litopenaeus vannemei broodstock.Experimental results are as follows.1,Temperature has a significant effect on egg laying amount and ovary development time of the female (P<0.01) as well as continuous spawning interval (P<0.05).The higher the temperature is, the larger the egg laying amount is and the shorter the ovary development time and the continuous spawning interval are when the temperature is below 30℃. Temperature over 30℃has a restraint on egg laying amount, ovary development time and continuous spawning interval. Ovary develops well at 30℃, the average egg laying amount is 16.6×10~4 cell/ind, the ovary development time is 143.2h and the continuous spawning interval is 75.0h.2,Temperature has a significant effect on sperm count, sperm activity and spermatophore development time of the male (P<0.01). The average sperm count reaches a peak of 10.5×10~6 at 26℃and the sperm activity is 66.4. With the temperature goes higher over 30℃, the spermatophore development time gets shorter and the sperm activity declines. The average spermatophore development time reaches the shortest by 140.8h at 34℃. Raising temperature is helpful to speed up the development of spermatophore.3,Salinity has a significant effect on egg laying amount, ovary development time and GSI of the female (P<0.01). The higher the salinity is, the higher the egg laying amount and GSI are and the shorter the ovary development time is. At salinity 30 the average egg laying amount is 17.3×104 cell/ind, the ovary development time is 145.2h and GSI is 0.049. Raising the salinity is helpful to increasing the egg laying amount and speeding up the development of ovary. Reduce the salinity can improve continuous spawning rate which reaches to 90.0% at salinity 20, but 60.0% at salinity 30 on the contrary.4,Salinity has a significant effect on spermatophore weight, sperm count and sperm activity (P<0.05).When the salinity is at a high level, the spermatophore weight is heavier, but the sperm count is less and the sperm activity is lower. Sperm count and sperm activity are higher at salinity range from 15 to 25, there is a restraint on sperm count and sperm activity at salinity over 25.5,Light intensity has a significant effect on ovary development time and egg size of the female(P<0.01).Light intensity below 1000 lx is good for shortening ovary development time and enlarging egg size. The average ovary development time reached a shortest by 171.2h, under the light intensity range from 100~1000 lx. The egg size is obviously larger than the other groups when the light intensity range from 10~100 lx. Light intensity over 10000 lx inhibits ovary development time, egg size and spawning rate obviously.6,Light intensity has a significant effect on spermatophore weight and sperm count of the male(P<0.01) as well as spermatophore development time(P<0.05). The average sperm amount reached its peak by 11.3×106 when light intensity range from 100~1000 lx. The average spermatophore development time become the shortest by 137.6h under the light intensity range from 10~100 lx. Spermatophore weight gets heaviest when light intensity range from 10~100 lx. Spermatophore weight and sperm activity get lower and spermatophore development time gets longer under light intensity over 10000 lx. Light intensity has little effect on the sperm activity and GSI (P>0.05). In general, light intensity below 1000 lx is suitable for gonad development of Litopenaeus vannemei.7,Diets has a significant effect on egg laying amount and ovary development time of the female(P<0.01)as well as the GSI(P<0.05). The average egg laying amount and GSI reach the highest by 16.6×104 cell/ind and 0.045 in group'mixture', while the average ovary development time reaches the shortest by 154.4h in group'Perinereis aibuhitensis'. Group'Perinereis aibuhitensis'and group'mixture'have an apparently effect on spawning rate and continuous spawning rate, the highest spawning rate is 95.0% in group'Perinereis aibuhitensis'and the highest continuous spawning rate is 83.3% in group'mixture'.Using Perinereis aibuhitensis and mixture diets consist of Perinereis aibuhitensis brings higher egg laying amount, GSI and shorter overy development time. Mixture diets consist of Perinereis aibuhitensis and other diets is helpful for ovary development of Litopenaeus vannemei.8,Diets has little effect on spermatophore weight, sperm count, sperm activity, spermatophore development time and GSI(P>0.05).9,Bacillus subtilis, Oocystis Borgei and Bacillus subtilis-Oocystis Borgei have a significant effect on spawning rate and continuous spawning rate. Spawning rate and continuous spawning rate are at 80.0% or more in all groups except untreated control group.10,Bacillus subtilis, Oocystis Borgei and Bacillus subtilis-Oocystis Borgei have a significant effect on sperm activity(P<0.01), which is lower in untreated control group, sperm activity is 52.1 in untreated control group while it is 62.2 or more in other groups.11,There is a significant restrain upon ammonia in group'Bacillus subtilis','Oocystis Borgei'and'Bacillus subtilis-Oocystis Borgei', their ammonia density have a reduction of 70.4%~75.2% compare with that of the untreated control group. Oocystis Borgei has a significant promotion on raising the level of dissolved oxygen in water.