Bulletinof the Japanese Society of Scientific Fisheries 38(7) 753-759 (1972) Amino Acids Essential for the Growth of Eels, Anguilla anguilla and A japonica* Shigeru ARAI**, Takeshi NOSE**, and Yoshiro HASHIMOTO*** (Received December 28, 1971) Essential amino acids for the species of eel, A anguilla and A japonica, were examined by using an amino acid test diet Forty fish were grouped in each aquarium and fed the test diets for a period of weeks In the both species, the fish fed diets deficient in each of alanine, aspartic acid, cystine, glutamic acid, glycine, proline, and tyrosine grew as well as those fed the complete amino acid diet The fish fed diets deficient in each of arginine, histidine, isoleucine, leucine, lysine methionine, phenylalanine, threonine, tryptophan, and valine failed to grow until the deleted amino acid was added to the ration It was thus established that eels require the same 10 kinds of amino acid reported to be essential for salmonids and others Ten amino acids have been shown to be essential for the growth of chinook salmon1), sockeyesalmon2), rainbow trout3), and channel catfish 4) by HALVEDR and his colleagues withamino acid test diets By examining the incorporation of 14C into amino acids after intraperitonealinjection of [U-14C]glucose, COEEYet al.5) indicated that the plaice and solehavea dietary requirement for amino acids similar to that of salmonids and channel catfish In the previous paper6), one of the authors reported that methionine, threonine, tryptophanand valine were found to be essential and proline to be non-essential for the growth of the Japanese eel, Anguillajaponica by using the amino acid test diet developed by HALVER7) for salmonids The results, however, were not so conclusive, since the test diet itself wasnot so satisfactory for the growth of eels This led us to study both the test diet and feedingtechnique for eels and establish a far more reliable testing method8) By using it, we examined the amino acids essential for the growth of species of eels, A anguilla and A.Japonica The results obtained clearly demonstrated that the both species of eel requirethe same 10 kinds of amino acid as reported on the other fishes Materials Experimental fish and Methods Elvers of A Japonica were obtained in March 1971, from Kago- shima Prefectural Fisheries Station and those of A anguilla in April 1971, from a wholesale 754 dealer of freshwater purified casein-gelatin ment was cm) and made aeration test source of were of the and carboxymethylcellulose fied practically basal weeks for thetized in diet both aquarium Saturday as moist eat the diet diet was cation by with reduced of out The eels acid in each and and diet this the weeks fed each in twice diet equal Co Table not Ltd modi- for days feeding with period g after fish a day was being were This made anes- grouped except extruded the the nearly was feeding, the which were 0.01 needle after in Ajinomoto Forty test without minutes diet, of after feeding preliminary nearest were pasty eiperi- supplied experimental of Thirty test gelatin leaving other simulated previous Table * L-arginine.HC1 basal to syringe was Before of The Fish and (20•~20•~ ingredients weighed The 25•Ž a mixture but feeding aquariums mixture other the liver Sunday into eels tank easy remainder to of the time established mixture to at intervals diet it The beef of minute product japonica a day nylon of A was w/v) once a 50-ml casein the fed loss at newly a binder, amino experimental were from replacing as of noodle diet each a received individual %, with soybean, start in acid replaced Tubifex, anguilla kept per experiments, of the heated liter a binder case (1.2 they siphoned cellulose growth Each as on A were water was anguilla the in a casein-amino feeding solution for when fine Test tion eels in 25•Ž at g fish of used of omitted in a urethane each and the on diet A start 0.6 0.4-0.7 acid-hydrolyzates the was of at weight and well rate weeks addition, before tanks body japonica and the was In immediately The A casein-gelatin and in Experimental at for kept order g in chloride kept casein were methods aquarium they amount in 1.7 polyvinyl each protein They diet8) testing of to diets, the fish approximately Feeding 50 live with was amino ingredients that work8) diet9) and of acid as the mixture, untouched the differed Composition used beef only liver basal adding (Table which slightly diet modifi- carboxymethyl1) sustained from after that The the of composiexcellent the amino of the basal diet 0, L-histidine HCI-H20 2.0, L-isoleucine 4.0, L-leucine 6.0, Llysine HCI 5.0, L-methionine 2.0, L-phenylalanine 3.5, L-threonine 3.0, L-tryptophan 1.0, L-valine 4.5, L-alanine 4.5, L-aspartic acid , 7.5, L-cystine 1.0, L-glutamic acid 10.0, glycine 5.0, L-proline 4.0, and L-tyrosine 3.0 g ** U S.P XII Salt Mixture No with trace metals91 *** Vitaminized cellulose powder The amounts of vitamins added to the diet were same as those reported by HALVER91 755 acid test diet adopted for salmonids and channel catfish Test diets were prepared by deletinga single amino acid from the basal diet by replacing it with a-cellulose powder The diet was finally adjusted to pH 6.2-6.5 with 25 % NaOH Results The average body weight at each weighing period and mortality Table for A anguilla and in Table for A japonica Anguilla anguilla The experiment was conducted are summarized in from June to July 20, 1971 The fish on the diets deficient in each of arginine, histidine, isoleucine; leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine showed a loss of appetite in days and apparent loss of body weight at the end of weeks Mortality was observed in some groups, especially in the lysine- and valine-deficient ones Fig Growth complete of the experimental fish, A anguilla (-0-; amino As shown in Fig 1, acid-deficient diet, -•œ-; diet) the detrimental effects of depletion of some amino acids were apparent at the end of weeks, and to all the groups of fish showing a retarded growth was then given the basal diet for weeks In the recovery test, the fish recovered their normal appetite within days and showed a rapid growth in the 2-week recovery period amino acids, arginine, threonine, tryptophan histidine, The percent body weight gain ranged from 19 to 49 These results clearly indicate that A anguilla requires 10 isoleucine, leucine, lysine, methionine, and valine as essential for the normal growth phenylalanine, On the other hand, the eels receiving diets lacking each of alanine, aspartic acid, cystine, glutamic acid, glycine, proline and tyrosine showed a growth comparable to that of fish on the basal diet, indicating that these amino acids are dispensable 758 Anguilla japonica 1971 The experiment was conducted from July 27 to September 6, As shown in Fig 2, the growth of eels was generally slow in the first 2-week period, but much improved in the second 2-week period, probably due to acclimation to the amino acid test diet ed in this case As mentioned above, the preliminary feeding with the basal diet was omittThe eels kept on the diets deficient in each of arginine, histidine, isoleucine, leucine, lysine, methionine, Fig Growth complete of the phenylalanine, experimental fish, threonine, A japonica (-0-; tryptophan amino and valine showed a acid-deficient diet , -•œ- diet) remarkable loss of their body weight The percent body weight loss ranged from to 15% for the first 2-week period and to 12% for the second period In the recovery test lasting for 2-weeks, the fish recovered their appetite within days as in the case of A anguilla, and the percent increase of body weight was 19-32 % in the recovery, test These results clearly demonstrate that there is no difference in essential amino acids between A japonica and A anguilla Discussion By using the newly established testing method, the amino acids essentialfor the growth of speciesof eel, A anguillaand A.japonica, wereclearlyrevealedto be the same as required by salmonidsand channel catfish It may be noteworthythat eels seemto be much more sensitive to the lack of essential amino acids A loss of appetitewas recognizedin a period as short as days, while in weeks on salmonids1-3)and channel catfish4) The recoveryof appetite in the deficienteels was also rapid, whenthe deleting essentialamino acid was added to the ration Although serine and hydroxyproline were not included in the basal diet, the eels attained nearly the same growth rate on it as on the casein-gelatin acids are therefore reasonably classified as dispensable for eels diet These amino In the previous worek6), the eels receiving the glycine-deficient diet showed a growth apparently inferior to that of the control In this experiment, however, dispensability of glycine was clearly demon- strated in the both species Acknowledgement This study was partly supported by a grant from the Ministry of Education The authors wish to express here their sincere thanks to Ajinomoto Co Ltd for the generous supply of amino acids and also to Kagoshima in collecting the experimental Prefectural Fisheries Station for assistance fish References 1) 2) 3) 4) 5) 6) 7) 8) 9) E HALVER,D C DELONO,and E T MERTZ: J Nutrition, 63,95-105(1957) J E HALVERand W E SHANKS: ibid., 72, 340-346 (1960) W E SHANKS,G D GABIMER,and J E 14ALVER: Prog Fish-Cult., 24, 68-73 (1962) H K DUPREEand J E HA.LVER: Trans Amer Fish Soc., 99, 90-92 (1970) C B CowEY, J ADRON,and A BLAiR: J Mar Biol Ass U K., 50, 87-95 (1970) T Nose: Bull Freshwater Fish Res Lab., 19, 31-36 (1969) J E HALVER: J Nutrition, 62, 245-254 (1957) S ARAI,T Nose, and Y HAsmMoTo: Bull Freshwater Fish Res Lab., 21, 161-178 (1971) J E HALVER: J Nutrition, 62, 225-243 (1957)  ... between A japonica and A anguilla Discussion By using the newly established testing method, the amino acids essentialfor the growth of speciesof eel, A anguillaand A. japonica, wereclearlyrevealedto... 25 % NaOH Results The average body weight at each weighing period and mortality Table for A anguilla and in Table for A japonica Anguilla anguilla The experiment was conducted are summarized... methionine, and valine as essential for the normal growth phenylalanine, On the other hand, the eels receiving diets lacking each of alanine, aspartic acid, cystine, glutamic acid, glycine, proline and