| Cipangopaludina cahayensis is a kind of freshwater snail with high health value which features fast growing,delicious flesh and rich nutrients and has become an important variety in domestic aquaculture.However,there are not enough studies on its reproductive biology,parental and larvae breeding methods.Without a sophisticated and effective artificial breeding technology,the source of larvae is still depends on natural propagation,its efficiency is low and limited large-scale breeding.To solve these above-mentioned difficulties,his paper illustrates the effect of reproductive biology and breeding density on growth and reproductive performance,induced spawning result of temperature as well as influence of the addition of algae powder on the growth of young C.cahayensis.With all of these researches,it provides theory basis and scientific proof for artificial breeding of C.cahayensis.The results are as follows:1.Reproductive Biology Basis of C.cahayensis(1)Male and female identification and group gender ratioTo identify the gender,observe the gonadal differences by exposing their shells in lamplight.The results are:gender can be identified by observing the different phenomena as lighting on the junction of the left spiral part and the body spiral layer.Female is like no obvious or particles shadow while shadow of male is like half-moon.After collecting the data for one year,it shows that the group gender ratio is 1.5:1.(2)Breeding capacity and habitsOne-year study of C.cahayensis on biopsy and cage-culture in rice field are observed.Result shows:snails absolute breeding capacity is significantly and positively correlated with their sizes.The average absolute breeding capacity of snails in 30?60mm is6.61?53.39.In natural condition,the breeding period of snail group is between March to October in which April is a peak.From April to October,the arvae are growing with a monthly increased weight of 0.38?0.58g.2.Effect of breeding density on growth and breeding performance of C.cahayensis(1)Effect of different breeding density on parental growth and breeding performance1260 parental snail each weighed 16?17g were selected and divided into 5 density clusters which are 20,40,80,120 and 160 per square meter.Three groups in each density were breeding in 60 days.It turns out that the growth and breeding performance of parental snail are decreased with an increased density.The best result shows in group of 20 per square meter in which the WGR and SGR are 10.75%and 0.17%.These two figures are higher than those in 40,80,120,160 which separately are 42.57%and 41.67%(P<0.05),130.69%and 112.50%(P<0.01),209.80%and183.33%(P<0.01),271.97%and 240.00%(P<0.01).In April,the number of average weight are 0.41g in 5 density group.The higher part than 40,80,120,160 groups are 115.79%(P<0.05),173.33%(P<0.01),272.73%(P<0.01),310.00%(P<0.01).It is suggested that the suitable breeding density of C.cahayensis is 16.70?16.80g,and the suitable breeding density should be 20?60/m~2.(2)Effects of different breeding densities on growth performance of larvae4500-5-day-old larvae each weighed 0.12?0.13g were selected and divided into 4density clusters which are 150,300,450,600 per square meter.Three groups in each density were breeding in 45 days.It turns out that the growth and breeding performance of larvae are decreased with an increased density.The best result shows in group of 150 per square meter in which the WGR,SGR and SR are 1386.54%,6.00%?87.78%.These three figures are higher than those in 300,450,600 which separately are 48.02%,15.38%and 12.38%(P<0.05),59.80%,19.05%and 28.52%(P<0.01),71.85%,22.45%and47.66%(P<0.01).It is suggested that the suitable breeding density of C.cahayensis is0.12?0.13g,and the suitable breeding density should be 150?300/m~2.3.Effect of temperature on the output of larvae C.cahayensis 50 snails each weighed 20g are selected to divide into ten in 5 groups in which the temperatures are 16?,20?,24?,28?and 32?.The induced labor experiment affected by temperature shows that the higher the temperature,the large the number of larvae.The best showed in 32?is 158 which is 52.67,9.87,1.88 and 1.72 times than that in 16?,20?,24?and 28?.The higher the temperature,the faster the larvae come out.The larvae came out after 3 hours in 24?,28?and 32?,7 hours in 20?and one day in 16?.Except for 80%surviving rate in 32?,the rest groups are all in 100%.This result shows that the most comfortable induced temperature is between 24?28?.4.The effect of algal powder on the growth of the larvae C.cahayensis891-5-day-old larvae were selected and divided into A,B,C,D,E,F,G,H,I groups.Three groups in each density were breeding in 30 days.Nine diets were formulated to contain Haematococcus Pluvialis meal,Chlorella meal,Spirulina meal,fresh mustard,basic feed,50%Haematococcus Pluvialisg meal+50%basic feed,50%Chlorella meal+50%basic feed,50%Spirulina meal+50%basic feed,50%fresh mustard+50%basic.The results showed that the growth of H group of 50%Spirulina meal+50%basic feed was the best,and its WGR and SGR were 90.91%and 2.16%.The WGR and SGR of E,F,A,I,B,C,and G were 80.00%(P<0.05)and 84.26%,43.32%and 50.93%(P<0.01),33.33%and 40.74%(P<0.01),23.33%and 29.17%(P<0.01),20.00%and24.54%(P<0.01),13.33%and 17.59%(P<0.01),10%and 12.96%(P<0.01)of H group.The SR of H group improve by 1.04%,4.30%,5.43%(P>0.05),7.78%,7.78%,11.49%,12.79%(P<0.05)and 18.29%(P<0.01)respectively than group E,F,A,C,D,I,G and B.In conclusion,50%Spirulina meal+50%basic feed could improve the growth and survival of larvae C.cahayensis. |
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