海水仔稚鱼早期阶段氨基酸的营养生理研究进展

深海海鱼鱼卵中的游离氨基酸占鱼卵总氨基酸含量的近50％（干重），游离氨基酸库中的游离氨基酸似乎是卵黄蛋白的水解产物。仔鱼吸收卵黄内源营养的过程中，游离氨基酸库中的游离氨基酸逐渐减少，到仔鱼开始摄食时，库中的游离氨基酸已近枯竭，游离氨基酸不仅是代谢能源，而且是体蛋白合成的基本原料，仔鱼开始摄食后，氨基酸作为分解代谢的重要物质，可能有高达60％的能量由氨基酸提供，由于仔稚鱼的生长主要是通过合成蛋白质增加鱼体的重量，加之仔稚鱼的生长速度很高，因此，仔稚鱼需要其饲料中有较高的氨基酸含量。仔鱼开始摄食后，其消化系统对蛋白质的水解和吸收能力较弱，海水仔稚鱼的早期阶段，仔鱼的肠道对游离氨基酸的吸收要高于对多肽和蛋白质中氨基酸的吸收，仔鱼开始摄食后，由浮游生物获得大量的游离氨基酸，用微粒饲料培育仔稚鱼，微脂粒技术可能是向饲料中添加游离氨基酸的实用技术。     

The amino acid profiles in developing eggs and larvae of the freshwater Percichthyid fishes,trout cod,Maccullochella macquariensis and Murray cod,Maccullochella peelii peelii

Results on changes in the total amino acids (protein bound + free) and the free amino acids (FAA) in relation to development, from egg (unfertilised and/or fertilised) to yolk-sac resorbed larva, before first feeding, in two Percichthyid fish, trout cod, Maccullochella macquariensis and Murray cod, Maccullochella peelii peelii, which lay demersal, adhesive eggs, are presented. Throughout development, the FAA accounted for only a small proportion (0.19 % in fertilised eggs of both species) of the total amino acid pool. Nine essential amino acids (EAA) and eight non-essential amino acids (NEAA) were quantified in the amino acid pool at all stages of development. In both species, the total amino acid content decreased during the transformation (at 20 ± 1 °C) from newly hatched larva to yolk-sac resorbed larva. Overall, the changes in the TEAA and TNEAA reflected that of the amino acid pool. In trout cod, all but one EAA (lysine) and two NEAA (cysteine and glycine) decreased with ontogeny, from fertilised egg to yolk-sac resorbed larva. In Murray cod, however, the exceptions to the general decline were two NEAA (aspartic acid and glycine). In contrast, the FAA increased with development, the changes being reflected in both FEAA and FNEAA. Qualitatively, the predominant free amino acids in trout cod and Murray cod eggs were alanine, lysine, leucine and serine. Because the egg protein and the total amino acid contents declined with development, it is concluded that the rate of breakdown of yolk protein was higher than the anabolic and catabolic processes during embryogenesis. Data also suggest that in freshwater fish FAA are an unlikely primary energy substrate during embryogenesis.     

Augmentation of free amino acids in eggs of red snapper,Lutjanus campechanus as part of the induced spawning protocol

An attempt was made to increase free amino acids (FAA) concentrations in eggs of red snapper Lutjanus campechanus as part of an induced spawning protocol. Mature female red snapper were given intramuscular injections of human chorionic gonadotropin (HCG) at a 1100 IU kg^?1 of female body weight. Immediately after the HCG injection, one set of females received an intramuscular injection of FAA in a buffered saline solution at a dose of 20 mg FAA cocktail kg^?1 of body weight. The FAA cocktail was 25% isoleucine, 25% leucine, 25% lysine and 25% valine on a molecular weight basis. A second set of fish did not receive the FAA supplement. Both sets of fish were equally successful in spawning with ovulation occurring 21–32.5 h post injection. Injection of FAA into brooders as eggs began final maturation and hydration resulted in an increase in leucine (nmoles mg egg^?1) and a slight increase in isoleucine (nmoles egg^?1) in recently ovulated eggs. FAA supplementation via brood injection altered FAA utilization rates by embryos and during larval development, resulted in a greater yolk sac and oil globule reserve in larvae as they approached the time of first feeding.     

Utilization of free amino acids, yolk proteins and lipids in developing eggs and yolk-sac larvae of walleye pollock Theragra chalcogramma

ABSTRACT:   To elucidate the utilization of the major yolk nutrient stocks in eggs and larvae of walleye pollock Theragra chalcogramma , the contents of free amino acids (FAA), the major yolk protein (180 kDa lipovitellin originated from vitellogenin B in ovulated eggs: oLv B), and lipids were measured. Most eggs hatched 18 days after fertilization at 5°C, and all larvae absorbed almost all their yolk mass by 28 days. The total FAA content showed no change during the first 6 days, and then decreased to 28% of the initial level by 18 days. The oLv B contents, measured by an enzyme-linked immunosorbent assay using a specific antiserum against oLv B, gradually decreased from 6 to 18 days, followed by a rapid decline. The content of phospholipids (PL) and triacylglycerols (TG) showed no marked change until hatching, and then decreased until disappearance of yolk sac. From these results, it is proposed that there are two main periods for nutrient utilization in embryos and larvae of walleye pollock. In the first period, FAA was mainly utilized until 18 days after fertilization. Active utilization of oLv B and lipids (PL and TG) instead of FAA occurred during the second period from 18 to 28 days.     

Urea and ammonia excretion by embryos and larvae of the African catfish Clarias gariepinus (Burchell 1822)

Yolk-sac larvae and starved larvae of Clarias gariepinus (Burchell 1822), reared at 28°C, were predominantly ammonotelic, but urea excretion contributed about 19±7% to the total nitrogen excretion. Exogenously feeding larvae of C. gariepinus were mainly ammonotelic until 180-205 h post fertilization, but from then on the relative urea excretion stabilized at 44±13%. The contents of total free amino acids (FAA) and ammonia in C. gariepinus peaked around complete yolk absorption. During the first period after hatching 64% of the FAA and 60% of the total ammonia were located in the yolk compartment. The body compartment contained the highest amount of FAA and total ammonia at the end of the yolk-sac period (65 and 77%, respectively). The amount of nitrogen originating from catabolism of amino acids was balanced within 6% by the excreted sum of ammonia and urea. The high degree of ureotelism in C. gariepinus larvae may constitute an adaptive mechanism to a habitat of temporal water shortage.     

Free- and peptide-based dietary arginine supplementation for the South American fish pacu (Piaractus mesopotamicus)

Arginine was hypothesized to be a model compound in the present study on molecular forms of indispensable amino acid (IAA) dietary supplementation. Juvenile South American pacu (Piaractus mesopotamicus) were fed diets containing arginine in a protein base (casein‐wheat gluten or casein‐gelatin), or the casein‐wheat gluten base supplemented with dipeptide or free arginine at two levels (5 and 10 g kg^?1). Growth and protein efficiency ratios were significantly affected by diets, but not by arginine molecular form. Three free dispensable amino acids (DAA) and four IAA in plasma were affected by diet, but plasma arginine concentrations did not differ. Plasma urea concentrations, being very low in the pacu, and hepatic arginase activities, were not affected by diet (P = 0.10–0.11), but together with plasma ornithine, mirrored the growth data. Molecular form of arginine supplementation, free or dipeptide, significantly changed several free IAA (Phe, Leu, Ile, His) and urea, with a higher mean plasma concentration in dipeptide fed fish. The dietary treatments, or molecular form of the arginine supplementation, did not change proximate composition, except that calcium levels decreased with higher dietary arginine supplementation level. The present study indicates that dipeptides can provide IAA to pacu, and that arginine supplemented in this form is utilized as efficiently as in free form.     

Amino acid profiles and amino acid utilization in larval African catfish (Clarias gariepinus): effects of ontogeny and temperature

The present study investigated the qualitative amino acid (AA) requirements of larval African catfish Clarias gariepinus. Yolk-sac larval AA profiles were measured at different temperatures and also in animals reared at 28 °C fed Artemia nauplii or an experimental dry diet. The AA profile of C. gariepinus larvae changed during ontogeny, especially before the start of exogenous feeding. The AA profiles of the food items (yolk, Artemia and the dry diet) differed considerably from that of the larvae. No selective absorption of yolk AA was detected. Higher temperatures led to increased absorption and depletion rates of AA, and also to a higher retention efficiency of yolk nutrients. However, changes in temperature did not induce preferential absorption or depletion of individual AA, and caused only small variations in the AA profile. Depletion rates of individual AAs varied, possibly due to differences between larval and yolk AA profiles, and also to changes in the larval AA profile during ontogeny. There was little regulation of catabolism of individual AA in yolk-sac and starved larvae, and no sparing of essential AA.     

Changes in free amino acid profile of red snapper <Emphasis Type="Italic">Lutjanus campechanus</Emphasis>, eggs,and developing larvae

The free amino acids (FAA) profile was determined for newly fertilized eggs and resultant larvae from wild-caught red snapper Lutjanus campechanus induced to spawn with hCG. Yolk sac and oil globule volumes of eggs and larvae were monitored over time from digital photographs. FAA profiles of the eggs and larvae were measured in picomoles (pmol) of FAA/mg of eggs by HPLC. Newly fertilized eggs had a mean total FAA content of 21.72 ± 3.55 nmoles/egg (92.81 ± 9.71 nmoles/mg eggs). Leucine, valine, lysine, and isoleucine were the most abundant essential FAA comprising 35.9% of the total FAA. Alanine, serine, asparagine, and glycine were the most abundant non-essential FAA comprising 34.2% of the total FAA. At 24 h post-hatch (hph) the mean total FAA had decreased by 81% since egg fertilization. The bulk of the FAA decrease was between the time of hatch and 12 hph. Only 8.5 ± 1.5% of the initial concentration in fertilized eggs of isoleucine, 9.7 ± 2.5% of arginine, and 9.9 ± 2.0% of threonine remained at 12 hph. Among the non-essential FAA, alanine dropped the most by 12 hph with 4.6% of the concentration found in a recently fertilized egg remaining, while cysteine had increased 254.7 ± 26.2%. The yolk sac volume decreased rapidly in the first 12 hph and was further reduced 77.0 ± 2.5% from 12 to 24 hph. The oil globule depletion rate was a more linear decline from fertilized egg to 36 hph.     

A simulation model for the metabolism of yolk sac larvae of the African catfish, Clarias gariepinus (Burchell)

Abstract. In fish larvae there is a strong natural selection for high yolk utilization efficiencies and high yolk absorption rates. Larvae with higher absorption and utilization will be larger at the onset of exogenous feeding, leading to higher survival and growth rates in the following stages of development. Modelling can be a powerful tool in clarifying the processes of fish larvae metabolism, providing the model is as explanatory as possible. The present model considers the larvae as a two-compartment system: the yolk sac and the larval body. This system exchanges oxygen, carbon dioxide, water, ammonia and heat with the environment. Yolk is absorbed through the syncytium, digested, and the resulting nutrients are released into the blood circulation. Circulating amino acids and fatty acids are considered to be used first for respiration, and what is left will be used for growth. From the moment that absorbed nutrients do not satisfy the energy needs, embryo tissue starts to be catabolized. Temperature is the only environmental factor which was assumed to affect significantly the metabolic processes. From the comparisons between simulations and experimental data, the simulations would appear to be accurate until complete yolk absorption, losing accuracy afterwards. Simulation outputs suggest that fat is the main energy substrate during yolk absorption, with protein becoming progressively more important, being predominant during starvation. Ideal culture conditions for African catfish yolk sac larvae seem to include: the highest temperature that combines with acceptable mortality rates; selection of broodstck towards obtaining the largest egg size, insofar as viability is not affected; the start of feeding as close as possible to 144 physiological day-degrees.     

Periodical changes of plasma free amino acid levels and feed digesta in yellowtail after feeding non-fishmeal diets with or without supplemental crystalline amino acids

ABSTRACT: Postprandial changes of free amino acid (FAA) concentrations in plasma and feed digesta contents were examined in yellowtail, Seriola quinqueradiata (220–280 g bodyweight) fed non-fishmeal diets either with or without supplemental crystalline amino acids (lysine, methionine, threonine, and tryptophan) in order to evaluate the availability of supplemental amino acids. Non-fishmeal diets containing 30% soy protein concentrate as the major protein source were prepared in three diet forms: soft dry pellet, extruded pellet, and single moist pellet. The level of plasma FAA and feed digesta content were determined at 0, 3, 6, 9, 12, 18, and 24 h after feeding. Plasma levels of four supplemental amino acids in fish fed the non-fishmeal diets with EAA were higher than those of fish fed diets without EAA, suggesting that yellowtail can efficiently absorb supplemental crystalline amino acids irrespective of diet form. However, a remarkable difference was observed in the periodical patterns of these four amino acids between FAA derived from supplements and those from feed protein. Moreover, FAA patterns in fish fed the non-fishmeal diets with EAA were different from those of the control fishmeal diet. Of note, methionine concentration was markedly high during the whole experimental period, resulting in an amino acid imbalance that may have caused lower feed performances in fish fed the non-fishmeal diets with EAA compared to the control fishmeal diet.     

Changes in lipid classes,fatty acids,protein and amino acids during egg development and yolk‐sac larvae stage in brill (Scophthalmus rhombus L.)

Brill (Scophthalmus rhombus L.) is a flatfish considered of special interest for aquaculture diversification, but the high mortality observed during the early larval rearing is the main obstacle to commercial culture. The objective of this study was to contribute to the knowledge of nutrient utilization of early‐hatched larvae, characterizing the changes in lipid and protein contents during embryogenesis and the yolk‐sac larval stage of S. rhombus. Total lipid, lipid classes and fatty acid contents remained constant during embryogenesis and yolk‐sac larval development, except for phosphatidylethanolamine and phosphatidylinositol, which increased in quantity during the yolk‐sac larval stage. On the other hand, total protein (including non‐protein nitrogen) and amino acids decreased their contents in both periods, especially at hatching. The decrease only in the serine, glutamic acid, proline and lysine contents during embryogenesis suggests a selective use of amino acids during this phase. Unlike embryogenesis, amino acids loss during hatching appears to be non‐selective, and almost all amino acids (essential and non‐essential) decreased. Our results suggest that there is higher catabolism of protein vs. lipid during embryogenesis and the yolk‐sac larval stage of S. rhombus.     

Comparative chemical,taste, and functional components in different tissues of giant grouper (Epinephelus lanceolatus)

The chemical composition, nutrition, and flavor components of various giant grouper tissues were determined. The muscle protein content was about 20%, and the muscle fat content was in the range of 3.9–6.4%, which is higher than that of most other groupers. The bone had the highest fat value (12.5–14.2%). The major nucleotide-related compound in the tissues was inosine monophosphate (IMP); whereas in the skin, adenosine monophosphate (AMP) was predominant. The predominant free amino acid (FAA) in the tissues was taurine (Tau), followed by arginine (Arg), lysine (Lys), and glycine (Gly). Tau content was higher in chin meat, and lower in bone. The total peptide content was in the range of 660–1,390 mg/100 g, which was much higher than that observed in other fish species. Muscle was rich in C16:0, C18:0, C18:1, and omega-3 highly unsaturated fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).     

Dietary indispensable amino acids profile affects protein utilization and growth of Senegalese sole larvae

In diet formulation for fish, it is critical to assure that all the indispensable amino acids (IAA) are available in the right quantities and ratios. This will allow minimizing dietary AA imbalances that will result in unavoidable AA losses for energy dissipation rather than for protein synthesis and growth. The supplementation with crystalline amino acids (CAA) is a possible solution to correct the dietary amino acid (AA) profile that has shown positive results for larvae of some fish species. This study tested the effect of supplementing a practical microdiet with encapsulated CAA as to balance the dietary IAA profile and to improve the capacity of Senegalese sole larvae to utilize AA and maximize growth potential. Larvae were reared at 19 °C under a co-feeding regime from mouth opening. Two microdiets were formulated and processed as to have as much as possible the same ingredients and proximate composition. The control diet (CTRL) formulation was based on commonly used protein sources. A balanced diet (BAL) was formulated as to meet the ideal IAA profile defined for Senegalese sole: the dietary AA profile was corrected by replacing 4 % of encapsulated protein hydrolysate by CAA. The in vivo method of controlled tube-feeding was used to assess the effect on the larvae capacity to utilize protein, during key developmental stages. Growth was monitored until 51 DAH. The supplementation of microdiets with CAA in order to balance the dietary AA had a positive short-term effect on the Senegalese sole larvae capacity to retain protein. However, that did not translate into increased growth. On the contrary, larvae fed a more imbalanced (CTRL group) diet attained a better performance. Further studies are needed to ascertain whether this was due to an effect on the voluntary feed intake as a compensatory response to the dietary IAA imbalance in the CTRL diet or due to the higher content of tryptophan in the BAL diet.     

The effect of live feeds bathed with the red seaweed <Emphasis Type="Italic">Asparagopsis armata</Emphasis> on the survival,growth and physiology status of <Emphasis Type="Italic">Sparus aurata</Emphasis> larvae

Larval rearing is affected by a wide range of microorganisms that thrive in larviculture systems. Some seaweed species have metabolites capable of reducing the bacterial load. However, no studies have yet tested whether including seaweed metabolites on larval rearing systems has any effects on the larvae development. This work assessed the development of Sparus aurata larvae fed preys treated with an Asparagopsis armata product. Live prey, Brachionus spp. and Artemia sp., were immersed in a solution containing 0.5% of a commercial extract of A. armata (Ysaline 100, YSA) for 30 min, before being fed to seabream larvae (n = 4 each). In the control, the live feed was immersed in clear water. Larval parameters such as growth, survival, digestive capacity (structural-histology and functional-enzymatic activity), stress level (cortisol content), non-specific immune response (lysozyme activity), anti-bacterial activity (disc-diffusion assay) and microbiota quantification (fish larvae gut and rearing water) were monitored. Fish larvae digestive capacity, stress level and non-specific immune response were not affected by the use of YSA. The number of Vibrionaceae was significantly reduced both in water and larval gut when using YSA. Growth was enhanced for YSA treatment, but higher mortality was also observed, especially until 10 days after hatching (DAH). The mortality peak observed at 8 DAH for both treatments, but higher for YSA, indicates larval higher susceptibility at this development stage, suggesting that lower concentrations of YSA should be used until 10 DAH. The application of YSA after 10 DAH onwards promotes a safer rearing environment.     

Nutrient and amino acid profiles of egg and larvae of Asian seabass, Lates calcarifer (Bloch)

Fertilized eggs and developing larvae of hatchery reared Asian seabass, Lates calcarifer (Bloch), were analyzed to determine the changes occurring in their proximate and amino acid (AA) composition. The fertilized dry egg weighed 31 μg and contained 13.71 μg (44%) protein, 8.48 μg (27%) lipid and 0.657 J of gross energy. Dry weight decreased by 39% during hatching. The protein, lipid and carbohydrate nutrients decreased by 4.86, 4.15 and 0.09 μg, respectively from egg to 2-days post hatching (dph) larvae (pre-feeding). The protein content of the spawned eggs and larvae were hydrolysed to AA in the laboratory. The fertilized eggs had a total AA content of 42% of their dry weight. The egg contained 1.287 μg, 1.132 μg, 0.964 μg, 0.942 μg, 0.787 μg and 0.713 μg of leucine, lysine, arginine, valine, threonine and phenylalanine, respectively and these six indispensable amino acids (IAA) constituted approximately 78% of the total IAA. In the early feeding stages of L. calcarifer larvae, the ratio of IAA/DAA increased from 0.797 in the pre-feeding stage to 1.632 after 2 days of feeding. During larval growth of L. calcarifer, the percentage contribution of isoleucine and leucine to total IAA contents increased, while it decreased for lysine, phenyl alanine and arginine. L. calcarifer larvae were found to have proteins, which are rich in glutamic acid, leucine and lysine, and poor in threonine and histidine, suggesting high dietary leucine and lysine IAA requirement. This revised version was published online in July 2006 with corrections to the Cover Date.     

Absorption, assimilation and catabolism of individual free amino acids by larval Atlantic halibut (Hippoglossus hippoglossus)

Following the completion of the lecithotrophic phase, most marine larvae rely on an incompletely developed digestive tract to absorb amino acids (AA) and other nutrients needed for rapid growth. Despite their undeveloped state, larvae must absorb nutrients in sufficient amounts to fuel exceptionally high rates of growth. This study examined the ability of larval Atlantic halibut to absorb, assimilate and catabolise dispensable (alanine, glutamate) and indispensable (arginine, lysine) dietary free amino acids (FAA) using tube-fed AA solutions with ¹⁴C tracers. Absorption of FAA was rapid with an average of 71% absorbed from the gut within 30 min after tube feeding. Evacuation of FAA by larvae was low, averaging only 6% of tube-fed dose. Dispensable amino acids (DAA) were catabolised in greater proportion (17%) than indispensable FAA (54%). Saturation of FAA transporters was not attained under the present conditions (20 mM, 20% midgut filling). Absorption rates did not differ significantly between the four FAA.     

Incorporation of yolk fatty acids into body lipids of goldfish (Carassius auratus L.) larvae raised at two different temperatures

In five separate experiments, eggs from a single female goldfish were fertilized at 20°C. They were incubated at 22°C for 6 hours, after which some of the eggs were transferred to 13°C. When a defined post-hatch developmental stage was reached, lipid extracts were prepared from larvae, both with yolk sacs intact and after removal of the yolk sac by dissection. Other larvae were sampled at yolk exhaustion. Gas chromatographic analysis of fatty acid profiles revealed that larvae incorporated 16:0, 18:0, 20:4 (n–6) and 22:6 (n–3) into their tissues in proportions higher than those present in the eggs from which they were derived. At 22°C, these trends were particularly apparent at yolk exhaustion. At 13°C, proportions of polyunsaturated fatty acids in the bodies of newly hatched larvae were higher than those in the 22°C larval bodies. Monounsaturated fatty acids were preferentially depleted during development, especially in larvae from high quality eggs. No dependence of egg quality, as assessed by larval viability at 22°C, on total egg lipid mass or fatty acid composition was found. Larvae from the lowest quality eggs showed a reduced preference for incorporation of (n–3) polyunsaturated fatty acids into their tissues.     

Effect of Salinity on Larval Rearing of Pacu,Piaractus mesopotamicus,a Freshwater Species

The aim of this study was to evaluate the growth and survival of pacu, Piaractus mesopotamicus, larvae reared in different salinities and to determine the Artemia nauplii life span in freshwater and in saline water. First feeding 5‐d‐old pacu larvae were reared in freshwater or at 2, 4, 6, 8, 10, 12, and 14 ppt salinities. The larvae were reared in 1.5‐L aquaria at a density of 10 larvae/L with three replicates per treatment. After 10 d of rearing, significant differences (P < 0.05) were observed for growth and survival. Larval growth was higher at 2 and 4 ppt, and survival at 2 ppt was 100%. In freshwater and at 4, 6 and 8 ppt, the survival was 91.1, 93.3, 73.3, and 39.9%, respectively. At higher salinities, there was 100% mortality after 2 h (12 and 14 ppt) and 8 h (10 ppt) of exposure. The slightly saline water of at least 2 ppt increased the Artemia nauplii life span compared to the life span in freshwater. Later, in a second trial, 5‐d‐old pacu larvae were reared in freshwater and at 2 and 4 ppt salinities during the first 5 or 10 d of active feeding, and then the fish were transferred to freshwater. At the end of 15 d, larval growth was lower in freshwater (42 mg) than in treatments 2 and 4 ppt (59–63 mg). The abrupt transfer of fish from freshwater to slightly saline water and the return to freshwater did not affect the survival rates (89–97%). The larvae were able to adapt to these saline environments and handle abrupt changes in salt concentration. We concluded that salinity concentration of 2 ppt can be used for pacu larval rearing, allowing the Artemia nauplii lifetime to last longer and cause faster fish growth.     

Free amino acid and protein content in the planktonic copepod Temora longicornis compared to Artemia franciscana

Previous studies have indicated that natural zooplankton, the natural prey organisms of marine fish larvae, is superior to enriched Artemia spp. nauplii in supporting survival, growth and normal development of pigmentation and eye migration in Atlantic halibut larvae. The present study was designed to compare the amino acid dynamics in copepods harvested from a natural lagoon with that of enriched Artemia franciscana nauplii. The natural zooplankton in the present study was dominated by Temora longicornis, but varied in its developmental stage composition, apparent nutritional quality, amount and availability. The protein content in natural zooplankton varied from 31% to 54% of dry mass (DM) compared to 31% in enriched Artemia nauplii. The amount of free amino acids (FAA) in relation to protein was 14% in enriched Artemia nauplii and varied between 16% and 27% in zooplankton in two consecutive seasons. The FAA composition of zooplankton in 1996 was unaffected by stage and season, and showed a species-specific pattern. In response to starvation, two patterns in the amino acid dynamics of copepods were found. The first, exhibited by the major nonessential amino acids (NEAA), showed a continuous reduction in individual amount, while the second pattern, exhibited by the minor nonessential amino acids and all the essential FAA, had an initial increase followed by a reduction. It is suggested that the protein amount in DHA Selco™ (INVE)-enriched Artemia nauplii is too low in order to maximise the growth potential of some marine fish larvae as cod and halibut.     

Changes in proximate and amino acid composition during early development of two Australian Percichthyid fish, Macquarie perch, Macquaria australasica Cuvier, and trout cod, Maccullochella macquarensis (Cuvier)

In the present paper, the results of a study on changes in the proximate and amino acid composition of the eggs and larvae of two Australian native Percichthyid fish, Macquarie perch, Macquaria australasica Cuvier, and trout cod, Maccullochella macquarensis (Cuvier), are presented. The stages of development studied were unfertilized and fertilized eggs, newly hatched larvae, and post-yolk-sac larvae (in Macquarie perch only). In Macquarie perch, significant changes in moisture content occurred throughout development, but this was not so in trout cod. The protein content (per cent dry weight) in Macquarie perch larvae only decreased significantly after hatching (P < 0.05). On the other hand, the total lipid (by dry weight) increased significantly during this transformation (P < 0.05), and decreased significantly in yolk-sac-resorbed larvae. In trout cod, the protein and lipid content did not change significantly up to hatching. The ash content increased significantly in newly hatched and yolk-sac-resorbed larvae of both species. The total amino acid contents of unfertilized eggs, fertilized eggs, newly hatched larvae and yolk-sac-resorbed larvae of Macquarie perch and trout cod were 5752, 4652, 3696 and 2723 μmol g^?1 (dry weight), and 4688. 3448 and 2329 μmol g^?1, respectively. In the amino acid pool in Macquarie perch, the essential amino acids (EAAs) leucine, isoleucine and valine, and the non-essential amino acids (NEAAs) alanine, aspargine and glutamate occurred in the greatest quantities in non-fertilized eggs, and the cysteine content was the smallest. In Macquarie perch, five out of nine EAAs (i.e. isoleucine, leucine, lysine, threonine and valine) and six out of eight NEAAs (i.e. alanine, asparagine, glutamate, glycine, proline and serine) decreased significantly (P < 0.05) from one developmental stage to the other. In trout cod, all the EAAs, barring lysine and all the NEAAs decreased significantly with development.