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The influence of diets complete in or free from either phospholipid (soybean lecithin) or n-3 highly unsaturated fatty acids (n-3 HUFA, squid liver oil) on the gonadosomatic index (GSI) and tissue lipid composition of ablated female Penaeus japonicus (mean weight=20.2±0.9g) were determined. Bilateral eyestalk ablation was performed 31-37 days after feeding on experimental diets and GSI was examined after 20 days of each prawn's ablation.Supplementation of both phospholipid and n-3 HUFA resulted in the highest GSI (3.0±0.8, P

A feeding trial was carried out to evaluate the nutritive value of soybean protein (SBP) for the juvenile freshwater prawn Macrobrachium rosenbergii (0.1g mean initial wet weight) compared with crab protein concentrate (CPC). Protein contents of the test diets ranged from 30 to 55% with an interval of about 7% and the dietary energy was kept constant (4.3 kcal/g) by adjusting carbohy-drate contents (α-starch and dextrin). Although the weight gain of CPC diet groups seemed to be higher than that of SBP diet groups at each protein level, no statistical significance was detected between SBP and CPC diet groups, with the exception of the prawns fed on the diet containing the second highest protein level (about 47%). There was a tendency for feed conversion efficiency (FCE) and protein efficiency ratio (PER) of SBP diet groups to be better than those of CPC diet groups in each protein level except for prawns fed on the second highest protein level (about 47%). The results above demonstrated that SBP could be a useful protein source for Macrobrachium diets. Protein levels tested in this study did not affect the growth, FCE, or PER in either CPC or SBP diet groups, which indicates the possibility of protein sparing by carbohydrate in M. rosenbergii. The proximate composition and amino acid pattern of the whole body were not affected by protein sources or levels.

In a series of studies to search for an optimal protein source for larval Penaeus japonicus feeding trials were conducted to determine the optimal combination of several protein sources with crab protein concentrate (CPC) on the larval development, growth, and survival of P. japonicus when fed on microbound diets. Although the addition of squid meal, brown fish meal, white fish meal, and krill meal to CPC improved larval performance compared to the single use of CPC, the magnitude of improvement by them was not as great as that by casein and soybean protein (SBP). In the diet containing both CPC and squid meal as the protein source, more CPC in the diet produced a poorer performance of larvae particularly at low levels of protein. Besides casein the best com-bination for larval development was CPC and SBP. The development, growth, and survival of larvae did not deteriorate when fed on CPC-SBP diets containing less than 30% of SBP. This study demonstrates that plant protein like SBP rather than squid meal as an additional source to CPC is available for good development, growth, and survival of larval prawn.

A stable form of vitamin C, L-ascorbyl-2-phosphate-Mg (APM), was tested for efficacy as a vitamin C source in the juvenile yellowtail Seriola quinqueradiata. The fish, weighing 2.67g, were fed 4 fish meal-based diets containing graded levels of supplemental APM (0, 3, 6, and 10mg/100g diet) for 83 days. The fish receiving the diet without supplemental APM showed deficiency sym-ptoms such as reduced growth rate, deformity (lordosis and scoliosis), distorted gill support car-tilage (degeneration of the ravine part of gill-cover), high mortality, and so on. The supplementa-tion of 3 to 10mg of APM/100g diet improved the growth and feed efficiency of the fish. The results of the feeding experiment indicated that a supplement of about 3 to 6mg APM/100g diet was sufficient to support good growth and survival and to prevent the gross vitamin C deficiency symptoms of the yellowtail. The supplementation of APM elevated the L-ascorbic acid (AsA) contents of serum and liver, serum alkaline phosphatase activity, and the ratio of hydroxyproline/proline in the bone. The results of the present study showed that APM can be effectively utilized by the yellowtail as a good replacement for AsA.

A microalga Nannochloropsis oculata is commonly used as a food for mass culture of the rotifer, Blachionus plicatilis. The nutritive value of rotifers for fish larvae is evaluated by the ω3 highly unsaturated fatty acids (ω3 HUFA), especially eicosapentaenoic acid (EPA) through the alga. To produce effectively the algal cells with high nutritive value, the changes of chemical components, crude protein, crude lipid, crude ash, fatty acids and amino acids in two strains of N. oculata during the growth were examined. The cells were cultured at 25°C and 3-4klx light and in low salinity condition 30‰. The initial cells (1×105 cells/ml and 4×105 cells/ml) were inoculated into the fertilized media in glass jars (10l) containing 100mg/l ammonium sulfate, 20mg/l calcium superphosphate, and 4mg/l Clewat-32. The contents of EPA and crude protein in the cells at the stationary phase reduced respectively to 60% and 66% (NRIA strain) or 35% and 40% (Chinese strain) in comparison with the exponential growth phase, which continued for 5-7 days after inoculation. The most effective production of N. oculata containing the highest EPA was estimated to be attained at about 7 days after inoculation under suitable conditions (25°C, S=30‰, 3-4 klx).

he sterol and fatty acid profiles in the bivalve Mactra chinensis were investigated for the hepatopancreas, gonad, mantle, gill, adductor muscle, and remainder. In all the organs and tissues, the major sterols were cholesterol (31.8-42.4%of total sterols), 24-methylcholesta-5, 22-dienol (17.5%), 24-methylenecholesterol (10.2-19.8%), cholesta-5, 22E-dienol (8.0-11.8%), and 24-methylcholest-5-enol (2.0-7.6%).The distribution of these sterols in the bivalve appeared to be uniform among the organs and tissues examined. This suggests that dietary sterols are not preferentially assimilated by this bivalve. The fatty acid profile of the hepatopancreas bore a resemblance to that of the gonad but differed from those of other organs and tissues. In the females, the hepatopancreas and gonad contained higher proportions of 14:0 and 20:5ω3 and lower proportions of 22:6ω3 than other organs and tissues.

The requirements of essential fatty acids (EFA) for Tilapia zillii were examined by feeding diets with several types of lipids and with different levels of ω6 and ω3 fatty acids. The addition of 18:2ω6, 20:4ω6, 18:3ω3 and 20:5ω3 to the diet containing 12:0 as a basal lipid improved the weight gain of T. zillii. However, the growth-promoting effects of 18:2ω6 and 20:4ω6 were superior to those of 18:3ω3 and 20:5ω3. These data indicated that T. zillii requires ω6 fatty acids rather than ω3 fatty acids. The dietary requirement of T. zillii for 18:2ω6 or 20:4ω6 was found to be about 1.0% in the diet. In the groups of T. zillii fed with the EFA-deficient diets, the levels of 20:3ω9 and 18:1ω9 increased, but they were decreased by the supplementation of either 18:2ω6 or 20:1ω6. Also, the supplementation of 18:2ω6 to the diets increased the proportion of 20:4ω6 in polar lipids of Tilapia bodies, indicating that T. zillii probably converts 18:2ω6 to 20:4ω6.

This study deals with the variation in the lipids of tissues during the molting cycle of prawn, Penaeus japonicus. During the molting cycle, the most notable variation in the lipid concentration (mg/100g fresh tissue) was seen in the hepatopancreas; the lipid concentration reached a maximum at stage D0 (beginning of premolt period). Also, the pre-ecdysial increase of hepatopancreatic lipids was found to be derived from both polar and neutral lipids. In other tissues such as the muscle, eyestalk, integument, and remains, the lipid concentration varied with the molting stages, but the variation was not as remarkable as observed in the hepatopancreas.

This paper deals with the release and transport of lipids in the prawn, Penaeus japonicus. The hepatopancreas obtained from the prawn after injection of palmitic acid-14C contained an abundance of radioactive phospholipids (PL) with rather large amounts of triglycerides (TG) and free fatty acids (FFA). When the in vivo prelabelled hepatopancrtas, containing mainly radioactive PL and TG, was reincubated in vitro in the prawn serum, PL, TG, and FFA were released into the incubation medium. Also, the in vitro reincubation of the predlabelled hepatopancreas containing mainly TG showed that TG was the major liped class released into the incubation medium. In addition, the present study suggests that the release of hepatopancreatic lipids in the prawn is accelerated by some factor (probably lipoproteins) of the prawn serum. These facts can be explained by the proposal that PL, TG, and FFA are the principal lipid moieties released from the hepatopancreas into the hemolymph in the prawn, P. japonicus.

Feeding experiments were conducted to examine the effects of algal diets, Chaetoceros gracilis or Chlorella saccharophila, on the sterol and fatty acid compositions of the pearl oyster Pinctada fucata. The pearl oysters were starved or fed with the algal diets for 30 days. Chaetoceros and Chlorella supported the growth of the pearl oyster during the period of 1 to 10 days to some extent, the former having a superior food quality to the latter. However, the pearl oysters seemed not toconsume algal diets substantially during the period of 10 to 30 days. Compared with the specimens at the start of the feeding trials, the pearl oysters receiving either Chaetoceros or Chlorella for 10 days contained low proportion of cholesterol and slightly high proportions of 24-ethyl-cholesterol and isofucosterol. However, the starved pearl oysters showed similarities to those receiving the algal diets in sterol compositions. These results indicate that the sterol composition of this bivalve is scarcely affected by the algal diets, suggesting that the sterol biosynthesis and turnover of dietary sterols proceed at a very slow rate. The 10-day feeding of Chaetoceros rich in 16:1 resulted in an increase in proportion of 16:1 in the pearl oysters. Chlorella contained large quantities of ω3-highly unsaturated farty acids (HUFA) such as 20:5ω3, The proportions of ω3-HUFA of the pearl oysters receiving Chlorella for 10 and 30 days were slightly higher than those of starved and Chaetoceros-fed groups but not so high as those of the specimens at the start of the feeding trials.

The distribution of radioactive lipid classes in the tissues of prawn, Penaeus japonicus, was investigated after oral administration of linolenic acid-1-14C in order to clarify the mechanism of lipid transport in crustaceans. Also, the movement of linolenic acid to the serous membrane site across the hin-dgut was examined by using the everted hind-gut of prawn. Dietary free fatty acid was presumed to be mainly absorbed at the region of the hepatopancreas and mid-gut rather than at the hind-gut. The absorbed linolenic acid was resynthesized to phospholipids (PL) in the hepatopancreas and hind-gut, and then released into the hemolymph as a form of PL. From this data, PL were conceived to be the most important mediators of lipid mobilization through the hemolymph in the prawn, P. japonicus.

This paper presents the variation in lipid compositions during the ovarian maturation of the prawn Penaeus japonicus. The ovarian lipid concentrations increased during the slight mature and yellow ovarian periods, remained at roughly constant levels during the subsequent ovarian period to spawning, and then decreased to low levels at the spent ovaries. The hepatopancreatic lipid concentrations increased with increasing maturity of the ovaries, reached a maximum level at the yellow period of ovaries, and then decreased during the subsequent period to spawning. These results suggest the possible movement of hepatopancreatic lipids to the ovaries during the ovarian maturation. Both triglycerides and phospholipids were responsible for the increase in ovarian lipid concentrations during the sexual maturation. The fatty acid composition of lipids, trigly-cerides, and phospholipids of the ovaries did not vary markedly during the ovarian maturation.

In order to define the nutritional role of dietary phospholipids (PL) in larval fish, the PL classes and possible fatty acid combinations of phosphatidylcholine (PC) were investigated on the food organisms such as the micro-algae and rotifers Brachionus plicatilis, post-larval prawns (P-30) Penaeus japonicus, and larval fish. PC and phosphatidylethanolamine were the major PL classes in a marine Chlorella (CH), Tetraselmis (TS), rotifers cultured with either CH or TS, red sea bfeam (40-days old) Chrysophrys major, knife jaw (30 days-old) Oplegnathus fasciatus, Ayu (74-days old) Ptecoglossus altivelis, and prawn. The major PC in the larval fish and prawn were those having fatty acid combinations of C16C20 (mainly C16:0, C20:5ω3), C16C22 (mainly C16:0C22:6ω3), and C18C22 (mainly C18:0C22:6ω3 and/or C18:1ω9C22:6ω3). Because larval fish are incapable of de novo synthesis of ω3-and ω6-series of fatty acids and also possibly have a limited ability for the synthesis of some PC, a part of these PC occurring in the larval fish may be derived from food organisms such as the rotifers which contained PC with fatty acid combinations of C16C20 (mainly Cl6:0C20:5ω3).

To clarify the transport mechanism of dietary lipids, the labelling pattern of lipid classes was investigated on the lipids extracted from the intestinal content, hind-gut, hepatopancreas, muscle, and hemolymph after oral administration of [14C] tripalmitin to the prawn, Penaeus japonicus. Besides this, the incorporation of radioactivity into serum lipoproteins was examined. Most of the radioactive serum lipids were associated with high density lipoproteins (HDL2 and HDL3) and very high density lipoprotein (VHDL), but not with low density lipoprotein, chylomicron, and very lowe density lipoprotein. The lipids of HDL2, HDL3, and VHDL contained polar lipids as the major radioactive lipid classes. The above data was discussed in relation to the lipid transport mechanism in the prawn, P. japonicus.

This paper presents the effects of destalking on the ovarian maturation and lipid compositions of the prawn Penaeus japonicus. The bilateral extirpation of eyestalks induced the ovarian maturation and increased the ovarian lipids with a concomitant decrease in the hepatopancreatic lipids. The increase in ovarian lipids was ascribed mainly to that in triglycerides (TG), phosphatidylethanol-amine, and phosphatidylcholine (PC), whereas the decrease in hepatopancreatic lipids was due mainly to that in TG and PC. These results suggest the transfer of body lipid reserves, particularly hepatopancreatic lipids, to the developing ovaries during the induced ovarian maturation of the prawn. The ovarian lipids, especially neutral lipids, of destalked prawns contained higher propor-tions of monoenes such as 16: 1 and 18: 1, and 22: 6ω3 and lower proportions of 20: 4ω6 and 20:5ω3 than those of non-destalked prawns.

The fate and turnover of cholesterol and β-sitosterol in the prawn Penaeus japonicus were investigated after the feeding of [4-14C] cholesterol and [22, 23-3H] β-sitosterol. Lipids were ex-tracted from the gut, hepatopancreas, hemolymph, muscle, and the remainder for analysis after 1, 24, and 240 hs of feeding of radioactive sterols. In the whole body, the half-lives (T1/2) of cholesterol and β-sitosterol were 5.4 days and 2.8 days, respectively. Cholesterol (T1/2=2.4 days) turned over at a faster rate in the hepatopancreas than β-sitosterol (T1/2=5.7 days), whereas cholesterol (T1/2=12.2 days) was retained in the muscle for a longer tiem than β-sitosterol (T1/2= 5.9 days). The prawn possessed the ability for conversion of β-sitosterol to cholesterol probably via 24-ethylidenecholest-5-enol and 24-methylenecholesterol. Ten days after feeding [3H] β-sitosterol, the whole body of the prawn contained large amounts of radioactive cholesterol (43% of total radioactive sterols).

This paper deals with the digestibility of various lipids and cholesterol in the prawn Penaeus japonicus which was determined by an indirect by an indirect method using chrominum oxide as an indicator. The prawn assimilated the lipids such as pollack liver oil, squid liver oil, soybean oil, oleic acid, palmitic acid, chicken-egg lecithin, tripalmitin, and hydrogenated fish oils effectively; the digestibilities of these lipids were more than 80% when the diets contained 8% levels of these lipids. The digestibilities of palmitic acid, tripalmitin, and chicken-egg lecithin were not affected markedly with their levels in the diets. Cholesterol added to the lipid-free diet was absorbed only slightly (% absorption=27.5). The co-existence of lipids such as palmitic acid, tripalmitin, or chicken-egg lecithin markedly improved the absorption rate of cholesterol, indicating the necessity of some lipids for effective assimilation of dietary cholesterol.

The larval and juvenile prawns Penaeus japonicus were maintained on purified diets with cholesterol alone and mixtures of cholesterol-sitosterol (1:1, 1:3, 1:10, 1:30, 1:100) to evaluate a cholesterol-sparing effect of sitosterol. The juvenile prawns had the highest weight gain (%), feed conversion efficiency (FCE) and protein efficiency ratio (PER) on the diet containing 0.5% cholesterol alone. The partial replacement of cholesterol with sitosterol reduced the weight gain, FCE, and PER inversely with increasing proportions of sitosterol. The body retention rates (%) of dietary proteins, lipids, total sterols, and cholesterol were lowered when dietary cholesterol was partially replaced with sitosterol. The larval prawns also grew best with the highest survival rate on the diet containing 1.0% cholesterol alone. The partial replacement of cholesterol with sitosterol (cholesterol/sitosterol ratios of 1:1, 1:3, 1:10, and 1:30) did not decrease the survival rates markedly but slightly retarded the larval development with increasing proportions of sitosterol. These results indicated that sitosterol had the cholesterol-sparing effect in terms of survival rates for the larvae but not for the juveniles, suggesting the change in sterol metabolism during the life cycle of the prawn.

This study deals with the variations in the content and fatty acid composition of lipid classes during the molting cycle of a fresh-water shrimp, Palaemon paucidens. The lipid content increased at mid premolt (stage D2) and then decreased at late premolt (stage D3-4). The accumulation of lipids during the early premolt period seemed to be attributed mainly to that of polar lipids. Throughout the molting cycle, the shrimp con-tained more polar than neutral lipids, the latter consisting mainly of triglycerides, free sterols, and free fatty acids. In the case of the polar lipids, the percentage composition of saturated acids such as 16:0 and 18:0 increased at stage D2. In contrast to the polar lipids, the tri-glycerides showed no marked variation in the fatty acid composition during the molting cycle. The free fatty acids showed an increase in saturated acids such as 16:0 and monoenoic acids such as 16:1 and 18:1 at intermolt (stage C).

The absorption and metabolism of dietary cholesterol-14C at various stages of the molting cycle in the prawn, Penaeus japonicus BATE, were studied. When the prawn was fed on the diet containing cholesterol-14C, radioactive compounds were absorbed from the digestive tract and widely distributed in all tissues and organs examined. High radioactivity was detected in the hepatopancreas and hypodermis of prawn. The concentrations of radioactive compounds were high in all tissues at stages C1-C2, C3-C4, and D1-D4 of the molting cycle, but low at stages B and D3-D4. Thin-layer chromatographic analysis of lipids demonstrated a high free sterol fraction (63-98%) and a low esterified sterol fraction (0-16%) in all stages of the molting cycle. Relatively high radioactivity was also found in the polar steroid fraction at stage B.

To clarify the growth-promoting effects of phospholipids, the prawn, Penaeus Japonicus, was maintained on various test diets containing a 7% level of pollack liver oil (PLO) and a 1% level of one of the following lipids: total lipids, acetone-soluble lipids (or neutral lipids), acetone-insoluble lipids (or polar lipids), lecithin fraction, cephalin fraction, sphingomyelin-glycolipids (1:1), fatty acids of lecithin isolated from the short-necked clam, Tapes philipprnarum, commer-cial phospholipids, animal cephalin, egg lecithin, and soybean lecithin. The highest weight gain was attained on the diet containing 7% PLO and 1% Tapes lecithin fraction. However, the fatty acids of Tapes lecithin did not exert such a growth-promoting effect. Also, soybean lecithin and egg lecithin had no effect. Tapes cephalin and animal cephalin were effective for the improvement of weight gain to some extent, but the growth-promoting effect of the two types of cephalin was not so as high as that of Tapes lecithin. These results suggest that the growth-promoting effect of Tapes lecithin is probably due to certain effects of the molecular form of Tapes lecithin itself.

The serum lipoproteins of the prawn, Penaeus japonicus, were separated by ultracentrifugation method. Most of the hemolymph lipids of this prawn, regardless of the sex, was associated with high density lipoproteins (HDL2 and HDL3) and very high density lipoprotein (VHDL), but scarcely with low density lipoprotein (LDL). No lipid was detected in the chylomicron, plus very low density lipoprotein fraction. As the lipid moieties, the HDL3 and VHDL contained abundance of polar lipids (PL) (65-85% of lipids), whereas the HDL2 involved substantial amounts of free sterols, diglycerides, and free fatty acids besides PL (40-47%). In every lipoprotein, the lipids contained palmitic, palmitoleic, stearic, oleic, eicosamonoenoic, eicosapentaenoic, and docosahexaenoic acids as the prominent fatty acids. This data was discussed in relation to the lipid transport mechanism in crustaceans.

The sterol components of the rotifer, Brachionus plicatilis, the marine type of Chlorella, Chlorella saccharophila, and the baker's yeast, Saccharomyces cerevisie, were investigated by using combined gas-liquid chromatography and mass spectrometry. The rotifer contained 24-methylcholesta-7, 22-dienol as a major sterol (61% of total sterols), and other sterols such as cholesterol, cholestanol, 24-methylcholesta-5, 22E-dienol, 24-methyl-cholest-22-enol, cholest-7-enol, 24-ethylcholesta-5, 22-dienol, 24-methylcholest-7-enol, 24-methyl-enecholest-7-enol, E-24-ethylidenecholest-7-enol, and Z-24-ethylidenecholest-7-enol. The Chlorella and baker's yeast used for the diets of rotifer contained mainly cholesterol and ergosterol, respectively. The present study also shows that the rotifer synthesize cholesterol from acetate-1-14C but not C28-and C29-sterols. Considering these data, we suspect that the sterols except C27-sterols occurring in the rotifer probably originate from dietary sources.

The diurnal variation was investigated on the fatty acids and sterols of rotifers during the feedback system culture using a baker's yeast and marine Chlorella. The rotifer contained abundance of monoene fatty acids (50-60% of total fatty acids) in every sampling time, but the levels of eicosapentaenoic acid (20:5ω3) was elevated after addition of the Chlorella. The sterol concentrations showed no marked varation during the feedback system culture, and the rotifer contained 24-methylcholesta-7, 22-dienol and cholesterol as the major sterols.

The present study demonstrated that the chiton, Liolophura japonica, the most primitive mollusk among the phylum Mollusca, was capable of converting cholesterol-4-14C to 7-cholestenol, probably via cholestanol. The significance of this result is discussed in relation to the sterol components of this mollusk. After injection of cholesterol-4-14C, radioactive metabolites were identified by thin-layer chromatography (adsorbents: Kieselgel G and silver nitrate-impregnated Kieselgel G) and preparative gas-liquid chromatograpgy on 3.0% OV-17. Finally, the identification of radioactive 7-cholestenol and cholestanol was confirmed by the constant specific activity (dpm/mg) during repeated crystallizations.

The effects of dientary prothin, lipid, and carbohydrate levels on growth and survivl of the pramn larvae were examined by the prawn larvae were fed 12 diets containing various of protein (casein;25, 35, 45, and 55%) and lipid (6.5, 11.5, and 16.5%)at a fixed carvohydrate level of 15%. In experiment2, the prawn larvae were given 9 diers containing vaious levels of protein (35, 45, and 55%) and carbohydrate (5, 15, and 25%) at a fixed lipid level of 6.5%. The effects of protein lecels on growth and survival of the pranwn varied with dietary carbohydrate levels but not with the dietary lipid leves. The elevation of lipid leves from 6.5% to 16.5% did not improve growth and survival when the diets contained suffcient leves (15% or more) of carvohydrate. Contrarily, the elevation od dietary carvohydrate lecels from 5 to 25% improved the survival of the prawn larvae when the diets xontained low levels (35%-45%) of protein. On the basis of these data, the opimum protein levels for the prawn larvae were estimated to be around 45%, 45%-55%, and 55% or more when the diets contained 25%, 155, and 5% levels of carbohydrate, resprctively.

The present investigation was undertaken to see the postprandial variation in lipid com-positions of the hepatopancreas, hemolymph, and muscle after feeding of the test diets with 3% soybean lecithin (diet A) and without supplemental phospholipids (PL) (diet D) to understand the nutritional role of dietary PL in the prawn Penaeus japonicus. Total lipid (TL) concentrations of the hepatopancreas and hemolymph were higher in the prawns receiving diet A than in those receiving diet D during the holding period from 1h to 6h after feeding. The increase of TL concentrations of the hepatopancreas was mostly attributable to that of neutral lipids (NL) such as triglycerides (TG) and cholesterol (CH), whereas that of the hemolymph was mainly due to PL such as phosphatidylcholine besides NL such as TG and CH. On the other hand, no re-mazkable difference was seen about the variation of lipid class concentrations of the muscle between the two diet groups as observed in the hepatopancreas and hemolymph. On the basis of these data, dietary PL was suggested to take some part in the transport of dietary lipids such as chole-sterol and triglycerides in the body through the hemolymph.

The lipid class and fatty acid composition of prawns fed either a fat-free diet or those containing 5% each of oleic acid, medium chain triglyceride (MCT), pollack residual oil (PRO), and 1% each of linoleic, linolenic and docosahexaenoic acids supplemented by 4% of oleic acid or MCT were determined. The high contents of lipids, in which triglycerides were major class, were obtained from the better growth groups of PRO, and docosahexaenoic and linolenic additions. Although prawns are able to metabolize parent acids, such as linoleic and linolenic acids, to ω6 and ω3 highly polyunsaturated fatty acids (HPUFA) in the same way as demonstrated in fish, it is probable that their conversion ability is less active. Comparing the polar and nonpolar lipids of prawns, the former was characterized by the higher proportion of HPUFA than the latter.

Feeding trials using purified test diets were conducted in order to clarify the requirements of essential fatty acids (EFA) for the larval stages of an Ayu Plecoglossus altivelis. The weight gains were low in the larvae fed on the lipid-free and ω3 fatty acid-deficient diets. The supplement of linolenic acid (18:3ω3) or eicosapentaenoic acid (20:5ω3) to the diet containing 8% levels of lipids, oleic acid (18:1ω9), or egg lecithin-18:1ω9 (3:5, w/w) improved the weight gain of the Ayu larvae, whereas that of linoleic acid (18:2ω6) enhanced growth very little. The growthpromoting effect of 18:3ω3 was almost equal to that of 20:5ω3. These results indicated that the larval Ayu requires 18:3ω3 and 20:5ω3 as EFA for growth.

A C27-sterol with a unique side-chain was isolated from a starfish, Leiaster leachii. The sterol was isolated from the complex sterol mixture of the starfish by using column chromatography on silver nitrate-impregnated silicic acid with hexane-benzene. The structure of this sterol was elucidated by gas-liquid chromatography, infrared absorption, mass, and nuclear magnetic resonance spectrometry. As a result, this sterol was identical with amuresterol, 22-trans-27-nor-(24S)-24-methylcholesta-7, 22-dien-3β-ol, a new sterol which had been quite recently isolated from another species of starfish, Asterias amurensis.