| Abalone is an important marine aquaculture economic species in China.The abalone aquaculture production in 2018 was 148500 tons and Fujian’s output accounted for 80%.however,the mortality caused by high temperature in Fujian has brought huge losses to the abalone aquaculture.In that way,the cultivation of new varieties of abalone is becoming more and more important to increase the yield.The hybrid progeny(’Green-Pacific abalone hybrid’)of green abalone(Haliotis fulgens)and Pacific abalone(H.hannai)has obvious growth and high temperature tolerance,but the mechanism of its growth advantage and the suitable temperature and diet are not clear.The research on the suitable growth conditions of ’Green-Pacific abalone hybrid’,has important biological significance and can provide reference for the aquaculture promotion of ’Green-Pacific abalone hybrid’.1.Effects of temperature and diet on growth rate,digestive enzyme activity of Pacific abalone and ’Green-Pacific abalone hybrid,The feed consumption rate,growth rate,digestive enzyme activity of different ages(one year old,two years old)Pacific abalone and ’Green-Pacific abalone hybrid,fed with Gracilaria lemaneiformis,Laminaria japonica,or formulated diet at 12,20 or 28℃ were measured and compared.The results of culture experiment showed that the survival rate of ’Green-Pacific abalone hybrid’ was significantly higher than Pacific abalone.The survival rates of Pacific abalone fed at 28 ℃ or with L.japonica were significantly lower than that at 12℃ or 20℃,but there was no significant difference in the survival rates of ’Green-Pacific abalone hybrid’ under different conditions.The growth rates of ’ Green-Pacific abalone hybrid’ were significantly higher than Pacific abalone except at 12℃,which might be related to the high feed consumption rate and low feed conversion rate of’Green-Pacific abalone hybrid’.The optimal growth temperature both Pacific abalone and hybrid abalone was 20℃.28℃was not suitable for abalone culture for the growth of feeding rate and feed conversion rate at 28℃.The growth rates of both Pacific abalone and hybrid abalone were the largest and the feed conversion rates were the smallest when feeding artificial diet,then G.lemaneiformis,at last L.japonica,which indicated that artificial diet was the best diet for abalone aquaculture.The digestive enzyme activity results showed alginate lyase activity and protease activity were significantly influenced by diet.Abalone fed with L.japonica or artificial diet had significantly higher alginate lyase activity than abalone fed with G.lemaneiformis,which might be because of the high content of alginic acid in L.japonica and artificial diet.Abalone fed with artificial diet had the largest protease activity might be because of the high content of protein.Cellulase activity showed a trend consistent with growth,suggesting that cellulase might be associated with the growth advantage of’Green-Pacific abalone hybrid’.The protease activity,cellulase activity and a-amylase activity of ’Green-Pacific abalone hybrid’ at 28 ℃ were significantly higher than those of Pacific abalone,indicating that digestive enzyme activity might be related to the high temperature tolerance of’Green-Pacific abalone hybrid’.2 Effect of temperature on energy budget of Pacific abalone and ’Green-Pacific abalone hybrid’The oxygen consumption rate,the absorption rate and the energy budget of the two ages(one year old,two years old)of Pacific abalone and ’Green-Pacific abalone hybrid’ at 12,16,20,24,28 ℃ were compared to analyze the growth advantage of’Green-Pacific abalone hybrid’ from the energy level.The experimental results showed that when the temperature exceeds 20 ℃,the absorption rates of both Pacific abalone and ’Green-Pacific abalone hybrid’ were significantly decreased,and the absorption rate was the lowest at 28 ℃.Oxygen consumption rate rised with increasing temperature.The oxygen consumption rate of 1 year old ’Green-Pacific abalone hybrid’ was significantly higher than that of Pacific abalone,which might cause it to have more energy to feed,so the feeding rate of one year old’Green-Pacific abalone hybrid’ was significantly higher than that of Pacific abalone.There was no significant difference in the oxygen consumption between two years old’Green-Pacific abalone hybrid’ and Pacific abalone but it might be due to the difference in size,which makes the feeding rate of ’Green-Pacific abalone hybrid’higher than Pacific abalone.The feeding rate,oxygen consumption rate,and feed absorption rate were converted into energy values to obtain the daily growth energy of each abalone.It also indicated that the growth rate and energy efficiency of abalone at 28 ℃ might be due to the decrease of absorption rate and the increase of oxygen consumption rate of abalone at 28℃.3 Effects of different factos on intestinal microbes of Pacific abalone and’Green-Pacific abalone hybrid’The intestinal flora of different ages(one year old,two years old)Pacific abalone and ’Green-Pacific abalone hybrid’ fed with Gracilaria lemaneiformis,Laminaria japonica,or formulated diet at 12,20 or 28℃ were measured and compared.The intestinal microbial result showed that the Proteobacteria,Tenericutes,Fusobacteria,and Bacteroidetes were the main intestinal flora of abalone.Temperature,diet and variety had significant effects on the intestinal flora of abalone.The intestinal flora of Pacific abalone was more affected by temperature,and the ’Green-Pacific abalone hybrid’ was more affected by the diet.Differential microbial analysis showed that Psychrilyobacter was the key differential flora of Pacific abalone and’Green-Pacific abalone hybrid’ at normal temperature and high temperature.Functional analysis found that the function of abalone gut flora was mainly sugar metabolism,amino acid metabolism,membrane transport,etc.Compared to ’Green-Pacific abalone hybrid’,the function of intestinal flora of Pacific abalone was imbalanced when temperature changes,which might be the reason for the high temperature tolerance and growth advantage of ’Green-Pacific abalone hybrid’.In the L.japonica group and 28℃group,functions of ’Green-Pacific abalone hybrid’ such as sugar metabolism,amino acid metabolism were upregulated while the genetic information transmission functions such as synthesis,mismatch repair,purine and pyridine synthesis were upregulated,indicating that intestinal flora function of Pacific abalone was unusual in these two environments,which was consistent with the survival data of the two abalones,indicating that intestinal microbes might affect the survival rate of abalone.Pacific abalone and ’Green-Pacific abalone hybrid’ seedlings were cultured in sea or factory.To explore the effects of different culture methods and size on abalone intestinal microbes,the extremely large and small individuals were collected to tested for their intestinal microbes.The result showed that size of abalone cultured in factory was significantly higher than that of aquaculture in the sea.Intestinal microbial analysis found that Proteobacteria,Tenericutes,Fusobacteria,and Bacteroidetes are the main intestinal flora of abalone.Proteobacteria were most abundant in the intestines of abalone cultured in the sea area,but the most common in the intestines of abalone cultured in factory was Fusobacteria,which indicates culture method had a significant effect on the intestinal microbes of abalone.The adonis analysis of abalone intestinal microbes find that culture method,variety and size had significant effects on the abalone microbes,and size had the least impact,about 3%,on the abalone intestinal microbes,The microbial difference analysis showed that the abundance of Psychrilyobacter in the abalone fed in factory was significantly higher than that in the sea area,and the significant different flora between the big-size Pacific abalone and’Green-Pacific abalone hybrid’ was also Psychrilyobacter,which indicated Psychrilyobacter might be related to growth rate.However,the abundance of different intestinal flora between big size and small size abalone was low and the function of these microflora was less studied,so this study had not yet found the difference between different sizes abalone.Functional analysis of abalone microbial microorganisms revealed that functions such as DNA replication,mismatch repair and other genetic information processing were up-regulated in the sea-cultured abalone,while the nutrient metabolism pathway of the factory cultured abalone was up-regulated,indicating that intestinal microorganisms had a more positive effect on factory cultured abalone. |
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