Effects Of Lysine And Methionine Enriched Artemia Nauplii On Growth, Digestive Enzyme And Associated Hormones In The Tongue Sole Postlarvae(Cynoglossus Semilaevis)

The tongue sole Cynoglossus semilaevis Günter is a common economic flatfishnear-shore of China sea. But the digestive tract of the C. semilaevis larvae are notfully developed and could not utilize microdiets successfully when they initiateexogenous feeding which is a crutial problem for mass production. Studies werecarried on about nutritional physiology of lysine and methionine for tongue solelarvae, and the results are presented as follows:1Effects of different enrichment material on the free amino acid in Artemianauplii was studied in this paper. There were4groups, including lysine group,Schizochytrium group, lysine plus Schizochytrium group and control group. Theexperiment lasted16hours, and was sampled every4hours. The results showed thatthe content of free lysine of Artemia nauplii in lysine group was significantly higherthan the other groups and4times higher than0h at the end of the experiment(P<0.05). And the content of lysine in Schizochytrium group reached the lowest.Except Thr, the content of other free essential amino acid and Asp, Ser, Gly, Tyr inlysine group were significantly higher than other groups (P<0.05). The content of, Thr,Ser, Gly, Ala, His and Pro of lysine puls Schizochytrium group decreased as the timeprolonged. But in other groups, the content of FAA all increased except Thr. Thevariation trends of the FAA level of the control group was similar to the lysine plusSchizochytrium group: except Thr, the content of FAA increased at the first4h,declined at8h, and increased at12h. But in lysine group and Schizochytrium group,the content of these FAA in Artemia nauplii increased during the first8h, declined at12h, then increased at16h. The results point that enriching Artemia nauplii withlysine is feasible and could increase the content of lysine and regulate FAA profile.2Effects of lysine and Schizochytrium enriched Artemia nauplii on growth performance, main digestive enzyme (amylase, acid protease, alkali protease) activity,alkaline phosphatase activity and hormone (cholecystokinin, thyroxin,triiodothyronine and cortisol) concentration in Cynoglossus semilaevis Günter (initiallength1.68±0.23cm)were studied in this paper. Postlarvae were divided into twoexperimental groups, including lysine group and Schizochytrium group, which werefed on Artemia nauplii enriched with lysine and Schizochytrium respectively. Andcontrol group was fed on Artemia nauplii without enrichment. Larvae were sampledfour times at four-day intervals, for16days. Results indicated that postlarvae of thecontrol group had the lowest growth throughout the experiment and the body lengthwas significantly lower than the other groups and the body weight was significantlylower than lysine group at12D (P<0.05). Alkaline phosphatase activity of controlgroup was significantly lower than lysine group at12D and was significantly higherthan Schizochytrium group at16D (P<0.05). Amylase activity of lysine group wassignificantly higher than Schizochytrium group at8D, which was significantly higherthan control group at12D and16D (P<0.05). No significant differences were found inacid protease activity between three different groups. Alkali protease activity ofSchizochytrium group was significantly higher than control group at12D and16D(P<0.05). Cholecystokinin (CCK) levels of lysine group reached3187.3pg/g at16D, which was significantly higher than control group (P<0.05). Significantdifferences between thyroxin(T4) and cortisol levels of the treatment groups were notfound at the end of study but concentration of triiodothyronine(T3) in lysine groupwas significantly higher than control group (P<0.05). The results indicate thatlysine-enriched Artemia nauplii feeding improved the growth, ingestion and thesecretion of CCK and T3of C. semilaevis postlarvae.3Effects of different enrichment material on the free amino acid in Artemianauplii was studied. The experiment was carried with4groups, including methioninegroup, Schizochytrium group, methionine plus Schizochytrium group and controlgroup. The experiment lasted16hours, and was sampled every4hours. The resultsshowed that the content of free methionine of Artemia nauplii in methionine groupwas significantly higher than Schizochytrium group (P<0.05). No significantdifferences were observed during all essential amino acids and nonessential aminoacids except Ser, Glu and Gly in control group was significantly higher thanmethionine plus Schizochytrium group at the end of the experiment (P<0.05). Thevariation trends of the FAA level in the control group was similar to the methionine group: the content of FAA declined at first and then increased, and the content wassimilar between0h and16h. But in methionine plus Schizochytrium group andSchizochytrium group, the content of these FAA in Artemia nauplii mainly declinedduring the experiment or slightly increaced, and then declined, and the content ofmost FAA was slower at16h than0h. The results point that enriching Artemia naupliiwith methionine is feasible and could increase the content of lysine but there is littleinfluence on FAA profile.4Effects of methionine and Schizochytrium enriched Artemia nauplii ongrowth performance, main digestive enzyme (amylase, acid protease, alkali protease)activity, alkaline phosphatase activity and hormone (cholecystokinin, thyroxin,triiodothyronine and cortisol) concentration related to digestion in the Cynoglossussemilaevis Günter (initial length1.67±0.14cm)were studied. Postlarvae were dividedinto three experimental groups, including methionine group, Schizochytrium groupand methionine+Schizochytrium group, which were fed on Artemia nauplii enrichedwith methionine, Schizochytrium and methionine+Schizochytrium respectively. Andcontrol group was fed on Artemia nauplii without enrichment. Larvae were sampledfour times at four-day intervals, for16days. Results indicated that postlarvae of theSchizochytrium group had the highest growth at the end of the experiment, and theweight was significantly higher than control group (P<0.05), length was significantlyhigher than other groups at12D. Alkaline phosphatase activity of Schizochytriumgroup was significantly higher than methionine group and control group at16D(P<0.05) and alkali protease activity was significantly higher than other groups at16D (P<0.05). The concentration of triiodothyronine(T3) in Schizochytrium group issignificantly higher than methionine group and control group at12D (P<0.05).Thyroxin(T4) content of Schizochytrium group was significantly higher than controlgroup at12D (P<0.05). Amylase activity of methionine+Schizochytrium group wassignificantly higher than methionine group at12D (P<0.05). CCK level of controlgroup was significantly higher than methionine+Schizochytrium group andmethionine group at4D (P<0.05), and was significantly higher than other groups orSchizochytrium group at12D and16D respectively. No significant differences werefound in acid protease activity between four different groups. Cortisol levels ofmethionine group was significantly lower than other groups at4D, and significantlylower than control group and methionine+Schizochytrium group at8D and16D(P<0.05), but alkaline phosphatase, amylase activity and T3and T4level was higher at the earlier stages of the experiment. We may conclude that methionine-enrichedArtemia nauplii feeding could slightly improve the growth and hormone levels of C.semilaevis larvae; it might indicate that the content of methionine in Artemia naupliicould mainly meet the requirement for C. semilaevis larvae.