Eggs of gilthead seabream Sparus aurata L. as a potential enrichment product of Brachionus sp. in the larval rearing of gilthead seabream Sparus aurata L.

The gilthead seabream Sparus aurata L. is a sequential spawner whose reproductive cycle can be manipulated to obtain year-round egg and fry production. Hence, there is an overproduction of eggs in commercial hatcheries that is normally wasted. Two feeding experiments were conducted with the purpose of investigating the potential use of fresh and freeze-dried gilthead seabream eggs for the enrichment of live preys. The first experiment was also designed to study the possibility of using freeze-drying as a conservation process for eggs in excess. Larvae were reared for 20 days after hatching (DAH),on a diet of Brachionus sp. As experimental controls, the commercial enrichment emulsion SUPER HUFA was used in the first experiment, and the microalgae Nannochloropsis sp. in the second. This study demonstrated the potential of gilthead seabream eggs as an enrichment product to be used in the feeding of the first larval stages of Sparus aurata L. The data obtained emphasize the need to have an overall perspective of the nutritional requirements of the organisms in culture.     

锯缘青蟹幼体饵料的营养强化

用酵母、水球藻、鱼油强化和豆油强化四种不同方式培养轮虫，再分别投喂锯缘青蟹幼体，分析测定轮虫和体的生化组成，结果显示，（1）不同方式培养的轮虫之间以及摄食这些轮虫的锯缘青蟹幼体之间的蛋白质含量都没有显著差异；（2）轮虫的脂类含量和脂肪酸组成与培养方式密切相关，小球藻轮虫的脂类含量最高，20：5n-3(EPA)占总脂肪酸的比例也最高 ，为18.05%，鱼油轮虫则含有最多的22：6n-3(DHA)，占总脂肪酸3.16%，脂类含量仅次于小球藻轮虫；（3）锯缘青蟹幼体的脂类含量和脂肪酸组成受相应饵料营养成分的影响。另外，幼体培育实验也发现，饵料营养成分影响幼体的存活率，结果表明，提高轮虫的EPA和DHA含量，尤其晨DHA含量，将有利于锯缘青蟹幼体的存活和发育。     

Essential fatty acid enrichment of cultured rotifers (Brachionus plicatilis, Müller) using frozen-concentrated microalgae

There is a growing interest in preserving microalgal preparations to maintain constant properties over a long period. The aim is to ensure sufficient delivery of essential fatty acids (and other key nutrients) to mollusc and crustacean larvae and to zooplankton used as live prey in the first feeding of fish larvae. For example, the rotifer Brachionus plicatilis has to be enriched with polyunsaturated fatty acids (PUFA) prior to fish feeding. We used four microalgal species [ Isochrysis galbana (T-ISO), Chaetoceros muelleri (CHGRA), Pavlova lutheri (MONO), and Nannochloropsis sp.] both as fresh culture or in a frozen-concentrated form to enrich rotifers. Overall, rotifers had similar relative fatty acid levels when fed the frozen-concentrated or fresh microalgal diets. The levels of 20:4n-6, 22:6n-3, and 20:5n-3 between B. plicatilis and the microalgal diets were linearly correlated. The fatty acid 20:4n-6 was the most readily assimilated: the content found in rotifers reached half the level measured in the microalgal diets. Our results indicate that both the fresh and frozen-concentrated forms of the four microalgal species can be used to enrich PUFA levels in rotifers. Further experiments should be conducted to test if assimilation differs when rotifers are enriched with mono- or multispecific microalgal preparations.     

Nutritional Enhancement of n-3 and n-6 Fatty Acids in Rotifers and Artemia Nauplii by Feeding Spray-dried Schizochytrium sp.

A docosahexaenoic acid (DHA), 22:6(n-3), rich strain of Schizochytrium sp. was used in a spray-dried form to evaluate the enhancement of highly unsaturated fatty acids (HUFAs) in Artemia franciscana nauplii (Utah biotype) and the rotifer Brachionus plicatilis . This heterotrophic microalga was selected because of its high concentration of the longest chain HUFAs in the n-3 and n-6 series, DHA and docosapentaenoic acid (DPA), 22:5(n-6), respectively. When 24-h-old Artemia nauplii were fed 400 mg/L of the algae for 24 h, the DHA content of the nauplii went from undetectable levels to 0.8% of dry weight and the omega-3 HUFA eicosapentaenoic acid (EPA), 20:5n-3, content went from 0.1% to 0.5% of dry weight in the nauplii. Similarly, 22:5(n-6) increased in the nauplii from undetectable levels to 0.4% of dry weight, with a concomitant increase in arachidonic acid, (20:4n-6), from trace to 0.3% of dry weight even though there was no arachidonic acid in the algal biomass. Similar enrichment patterns were observed in rotifers. The results suggest that spray-dried cells of Schizochytrium sp. are effective in enriching Artemia naupli and rotifers in both n-3 and n-6 HUFAs. The results also suggest that Artemia nauplii and rotifers are capable of readily retroconverting 22:6(n-3) to 20:5(n-3) and 22:5(n-6) to 20:4(n-6) through the process of β-oxidation, a well-known process in mammals.     

An Intensive Approach to Atlantic Halibut Fry Production

The larval stage is regarded to be the main bottleneck of halibut production. Halibut eggs were obtained from captive broodstock both by stripping and by natural spawning. Artificial photoperiods were used to increase the total spawning season. Yolk sac larvae are presently produced either in small stagnant units or in large flow through systems. A major consideration is to avoid stress of the larvae, caused by mechanical disturbances of the larvae and by high bacterial load or high ammonia levels in the water.
The experiments showed that halibut larvae began to ingest algae earlier than rotifers Brachionus sp. Supplementation of algae to first feeding tanks resulted in enhanced survival and growth rate of the larvae. Both rotifers and Artemia can be enriched with very high levels of highly unsaturated n-3 fatty acids (n-3 HUFA). Enriched live feed, containing high levels of n-3 HUFA and total lipids, enhanced both survival and growth of the halibut larvae. The highest growth rates were obtained with wild zooplankton and addition of algae, but enriched cultivated feed combined with algae resulted in growth of the same magnitude as with wild zooplankton.     

Replacement of fresh algae with commercial formulas to enrich rotifers in larval rearing of yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

This study compared the efficacy of four products that are commonly used in hatchery for nutritional enhancement of rotifer Brachionus plicatilis as the starter food for yellowtail kingfish Seriola lalandi larvae. This experiment consisted of one fresh algae and three enrichment products: (1) Fresh algae were a mixture of Nannochloropsis and Isochrysis at 2:1 on a cell concentration basis; (2) S.presso, (Selco S.presso ^®, INVE Aquaculture); (3) Algamac 3050^® (Aquafauna, USA); (4) Nutrokol ^® (Nutra‐Kol, Australia). Survival rates of the fish fed rotifers enriched with fresh microalgae (40.69%) and S.presso (31.21%) were higher than those fed Algamac 3050 (10.31%). On 3 day post hatch (DPH), fish feeding incidence in the fresh algae treatment was significantly higher than that in other treatments. On 6 DPH, fish showed the lowest feeding incidence in the Algamac 3050 treatment. The methods of enrichment did not affect total lipid levels in either rotifer or fish larvae, but Algamac 3050 enrichment achieved the highest DHA/EPA ratio and lowest EPA/ARA ratio in both rotifers and fish larvae. This study indicates that fresh algae can be replaced by S.presso, but Algamac 3050 is not as good as other formula for rotifer enrichment in rearing yellowtail kingfish larvae in this system.     

Enriching rotifers with “premium” microalgae. Isochrysis aff. galbana clone T-ISO

The effect of semi-continuous culture on the nutritional value of microalgae was tested in the rotifer Brachionus plicatilis in short-term enrichment experiments. Isochrysis aff. galbana clone T-ISO was cultured semi-continuously with renewal rates from 10 to 50% of the volume of the culture per day and used to feed the rotifers. After 24 h, dramatic differences in dry weight and protein, lipid and carbohydrate contents were observed in the rotifers depending on the renewal rate applied to the microalgal culture. Rotifers fed T-ISO cultured with low renewal rates showed low dry weight and organic content, whereas rotifers fed microalgae from nutrient-sufficient, high renewal rate cultures showed higher dry weight and increases up to 60% in protein, 35% in lipid and 100% in carbohydrate contents. Feed conversion rate (FCR) and organic FCR decreased with increasing renewal rates, indicating a more efficient assimilation of the microalgal biomass obtained at high growth rates. The fatty acid profile of rotifers reflected that of T-ISO, with maximum content of polyunsaturated fatty acids (PUFAs), n-3 fatty acids and docosahexaenoic acid (DHA) being found in the rotifers fed microalgae from the renewal rate of 40%. Results demonstrate that the biochemical composition of B. plicatilis is strongly modified through the use of semi-continuous cultures of microalgae in short-term enrichment processes. This technique provides an excellent tool to improve the nutritional value of the live feed used in fish larvae cultures.     

Nutritional Properties of the Marine Rotifer Brachionus plicatilis Fed the Freshwater Microalgae Selenastrum capricornutum

This study examined the effects of storage time on the fatty acid composition of freshwater Selenastrum capricornutum algal paste under 4 C refrigeration, the fatty acid composition of rotifers fed the fresh and stored algal paste, and the toxicological properties of the algal paste. Microalgae were produced in a hydraulically integrated serial turbidostat algal reactor (HIS-TAR), harvested as a paste, refrigerated and analyzed every 2 wk. Fresh Selenastrum capricornutum paste had almost three times greater concentration of unsaturated fatty acids than saturated fatty acids. Over 50% of the unsaturated fatty acids were made up of n-3 and n-6 fatty acids. Total unsaturated, n-3 group and n-6 group fatty acids decreased ( P 0.05) during storage, including the nutritionally important fatty acids (C20:4n6, C20:5n3, C22: 6n3). Rotifers fed 2– and 4-wk-old algal paste had a significantly lower ( P 0.05) total unsaturated fatty acid percentage and significantly greater ( P 0.05) total saturated fatty acids than those fed fresh algae. There were no significant changes in the n-6 group fatty acid level in the 4-wk-old paste feeding study or for the n-3 or n-6 groups in the 2-wk-old paste feeding study as compared to fresh algae. The levels of the three nutritionally important fatty acids (C20:4n6, C20:5n3, C22:6n3) did not differ between rotifers fed fresh and stored algae. Stored algae did not present toxicity to rotifers and Daphnia at the normal feeding concentration. These results indicated that the use of refrigerated freshwater algal paste for production of rotifers results in live feed with adequate nutritional properties for marine larviculture. This could eliminate the costs associated with production of marine algae, which could be replaced with freshwater algae, and may provide an alternative to cryopreservation.     

The effect of different HUFA enrichment emulsions on the nutritional value of rotifers (Brachionus plicatilis) fed to larval haddock (Melanogrammus aeglefinus).

A feeding study was conducted in the winter 2001 to determine the effects of feeding rotifers (Brachionus plicatilis) enriched with various levels of essential fatty acids on the growth and survival of haddock larvae (Melanogrammus aeglefinus). Rotifer enrichment treatments were: 1) mixed algae, 2) high DHA (docosahexaenoic acid, 22:6n-3), 3) high DHA and EPA (eicosapentaenoic acid, 20:5n-3), and 4) DHA, EPA, and AA (arachidonic acid, 20:4n-6). Larvae were fed rotifers enriched with the different treatments from days 1 to 16 post-hatch. From day 17 until 25 all treatment groups were fed rotifers reared on mixed algae and then weaned onto the International Council for Exploration of the SEA (ICES) Standard Reference Weaning diet (http://allserv.rug.ac.t/aquaculture/rend/rend.htm) over a five day period. The experiment was terminated on day 41 post-hatch. The enrichment treatments affected the fatty acid composition of the rotifers and correlated with the accumulation of these fatty acids in the haddock larvae. However, no significant differences in larval growth or survival to 40 days post hatch were detected, suggesting that all treatments provided the minimal essential fatty acid requirements for haddock.     

The Effects of Enriching Live Foods With Highly Unsaturated Fatty Acids on the Growth and Fatty Acid Composition of Larval Red Drum Sciaenops ocellatus

Three experiments were carried out to test the effects of enrichment of live food (rotifers) with varying levels of n-3 highly unsaturated fatty acids (HUFA) on the growth rate and fatty acid composition of red drum larvae. Additionally, the fatty acid compositions of red drum eggs and day-1 larvae were compared. The enrichment techniques were successful in that the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were elevated in the rotifers fed the enrichment diet. Red drum larvae fed the control rotifers produced the highest growth rate of the three experiments. Larvae fed rotifers with no HUFA supplement (NHUFA) had a significantly lower growth rate than the controls for that experiment. The fatty acid compositions of the eggs and day-1 larvae did not vary significantly and contained high levels of 16:0, 16:1 n-7 and DHA (22:6 n-3). Based on these data, the lack of DHA in the diet significantly reduced the growth rates of larval red drum. The 10-day-old red drum larvae had similar fatty acid profiles at the end of the experiments regardless of the diet they were fed, indicating that dietary inputs have little effect on the fatty acid composition of larvae during the first ten days of growth. Red drum larvae appear to have the ability, though limited, to bioconvert EPA to DHA since there was a significant increase in the levels of DHA from day 1 to day 10 in the NHUFA larvae. However, the efficiency of this bioconversion is not sufficient for optimal growth and supplemental DHA at least to the level found in the control rotifers (0.3–0.4mg/100mg tissue) is necessary to maximize growth. The exact role of EPA could not be determined from this study due to the inability to produce an EPA-free rotifer.     

Production, disinfection and evaluation for aquaculture applications of rotifer resting eggs from Bohai Bay, P.R. of China

The dynamics of resting egg production of the rotifer Brachionus plicatilis originating from a wild population in the Tanggu Saltworks (P.R. China) was investigated. In the natural environment as well as in semi-controlled rearing conditions an increased resting egg production was noticed with declining food availability. Processed resting eggs had a hatching efficiency of 3 x 10 6 rotifers per gramme irrespective of their origin. Hatching started 22 h after the initiation of incubation and was completed after 36 h. Rotifers obtained from resting eggs could be further cultured on Culture Selco® and enriched with Super Selco®. The fatty acid profile of these rotifers were not divergent from reference rotifers (originating from the Laboratory of Aquaculture and Artemia Reference Centre) demonstrating that this strain was not catabolizing essential fatty acids and could be used for enrichment purposes. Storage of resting eggs at 4°C resulted in a 50% lower hatching after 1 year but remained stable during the next 2 years. The resting eggs used for storage could easily be disinfected without affecting their hatching characteristics. These results indicate that this material could be used as inocula for mass cultures of live food for commercial hatcheries.     

几种单胞藻对褶皱臂尾轮虫的营养强化研究

利用气相色谱法测定了小球藻、牟氏角毛藻、球等鞭金藻和投喂不同藻类后12h的褶皱臂尾轮虫的脂肪酸含量。试验结果表明,不论是投喂单种藻类还是2种混合藻类,强化后的轮虫其体内的脂肪酸含量均发生了明显变化,其中单链脂肪酸及低度不饱和脂肪酸的含量在投喂前后没有变化,各种脂肪酸的含量界于未强化的轮虫和所投喂的单胞藻饵料含量之间。3种高度不饱和脂肪酸的含量,除了二十二碳六烯酸因在牟氏角毛藻中含量较低,在单独投喂牟氏角毛藻后的轮虫中未检测出外,其余均与其所投喂的单胞藻的脂肪酸一致;轮虫中被检出的3种高度不饱和脂肪酸的含量,在单种藻类试验组中均低于所投喂藻类的含量;在2种藻类混合试验组中界于2种单胞藻含量之间。混合藻类比单种藻类强化轮虫具有更加全面的营养效果。     

Enrichment of Rotifers Brachionus plicatilis with Eicosapentaenoic Acid and Docosahexaenoic Acid Produced by Bacteria

Abstract— Two bacterial strains, rich in either eicosapentaenoic acid [EPA, 20:5(n-3)] ( Shewanella gel-idimarina ACAM 456) or docosahexaenoic acid [DHA, 22:6(n-3)] ( Colwellia psychroeryrhrus ACAM 605) were tested for their ability to enrich rotifers Erachionus plicatilis in these polyunsaturated fatty acids. Rotifers were exposed for 24 h to each bacterial strain and to a mixture of the two strains. They were then harvested and their fatty acid compositions were analysed and compared to those of rotifers that had been either starved or fed yeast Saccharomyces cerevisiae or microalgae Tetraselmis suecica in 2-L glass flasks. Exposure to 1.4 × 10⁹ cells/ml of the EPA-producing bacterium only resulted in rotifer EPA levels increasing from 0.1% to 1.2% of total dry weight (%dw). Similarly, following exposure to 1.0 × 10⁹ cells/mL of the DHA-producing bacterium only, rotifer DHA levels increased from below detection to 0.1% dw. When exposed to a mixture of the two bacterial strains, containing 7.0 × 10⁸ celldml of the EPA producer and 5.0 × 10⁸ cells/mL of the DHA producer, the rotifers'final EPA and DHA levels were 0.5% dw and 0.3% dw respectively. Although feeding strategies need refining, these results show, for the first time, that rotifers can be enriched with DHA from bacteria, and that rotifers can be enriched simultaneously with both DHA and EPA from different bacterial strains.     

Importance of Docosahexaenoic Acid in Marine Larval Fish

Marine finfish require n-3 HUFA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as essential fatty acids (EFA) for their normal growth. But it remained unclear as to which of the n-3 HUFA, either EPA or DHA, was important. Unlike the freshwater species, the EFA efficiency of EPA and DHA may vary in marine fish. The developing eggs rapidly utilize DHA either for energy or for production of physiologically important substances like prostaglandin.
This report reveals that in marine larval fish DHA is superior to EPA as EFA. In the case of red seabream, feeding rotifers incorporating EPA and DHA or an n-3 HUFA mixture prevented many of the ill-effects observed when the rotifers were low in n-3 HUFA. Apart from the best growth and survival in an activity test for the larvae fed on DHA-rotifer, the incidence of hydrops seemed to be totally prevented dietetically by DHA. Similar results were obtained in larval yellowtail, striped jack, striped knifejaw and flounder. There seems to exist a functional difference between EPA and DHA.     

Nutritional composition of rotifers following a change in diet from yeast and emulsified oil to microalgae

Rotifers, Brachionus plicatilis, fed baker's yeast and a lipid emulsion (High DNA Super Selco, INVE Aquaculture NV Systems SA, Belgium), were harvested and fed Isochrysis galbana for 72 h, the nutrient composition was analysed during this period. The enrichment effect on the rotifers following transfer to I. galbana was most pronounced for ascorbic acid and thiamin. I. galbana seemed to contribute very little as a source of the lipid-soluble vitamins. Most of the minerals and trace elements were unaffected by the transfer to I. galbana, but Fe, Mn, As and Cd increased, Cu and Ni decreased whereas the effect on Cr and Mo were uncertain. The fatty acid composition of the rotifers changed towards the composition of I. galbana during the experimental period. Intermediate glycogen levels were measured in the rotifers at all sampling times. With the exception of lysine, serine and proline, all amino acid levels seemed to be unaffected by the transfer to I. galbana. This study showed that transfer of rotifers to microalgae (I. galbana) feeding had a positive effect on nutritional value. Macronutrients were maintained at adequate levels, and algal feeding improved the nutritional quality of rotifers with respect to water-soluble vitamins. Changes in rotifer nutrient composition are discussed in relation to nutritional requirements of fish larvae.     

Fatty acid analysis of fish eggs without solvent extraction

Two techniques for preparing samples of Coryphaena hippurus fish eggs for fatty acid analysis were compared. The first technique involved direct methylation of samples containing either 50 or 100 fresh eggs. The second involved methylation of the solvent-extracted fat from samples containing 1000 eggs each that had either been freeze dried or oven dried. The fatty acid profiles of small samples of fresh eggs were similar to profiles obtained from the solvent-extracted fat of much larger samples of dried eggs. In addition, the fatty acid profiles of 100 fresh egg samples were higher in both saturated and unsaturated fatty acids than the profiles obtained from 100 freeze-dried or oven-dried eggs. The technique of using direct methylation of fresh egg samples without solvent extraction has three main advantages: it requires less preparatory and analytical work, it can be used with much smaller samples, and it is less destructive to the material being analyzed. Direct methylation can also be used to prepare samples of small organisms such as algae, rotifers (Brachionus sp.), and brine shrimp (Artemia sp.) for fatty acid analysis.     

Fatty acid profiles of two freshwater fish larvae (gudgeon and perch) reared with Brachionus calyciflorus Pallas (rotifer) and/or dry diet

The efficiency of the rotifer Brachionus calyciflorus Pallas as a nutritional source for rearing larvae was studied in a coldwater cyprinid, the gudgeon Gobio gobio (L.), and in a percid, the perch Perca fluviatilis L., through their composition in fatty acids. Rotifer intake affected the fatty acid profiles of the larvae significantly, with an especially remarkable presence of the linoleic family. In gudgeon fed with rotifers, the polyunsaturated fatty acids (PUFA) reached 10.98% of the dry weight of the sample. This rate was highly influenced by the presence of the acids C18:2n-6 and C22:6n-3 which represented 66% of the total PUFA. In perch fed exclusively with rotifers, the PUFA represented 7.27% of the dry weight. In both cases, the ratio n-3/n–6 decreased by 75% and 73% after 10 days of feeding with B. calyciflorus. This variation was probably due to the exogenous supply in acids of the linoleic family through the rotifers and to the fact that these two species of fish seem to favour the mobilization of the n-3 PUFA such as C22:6n-3 for growth and survival. Moreover, with the utilization of rotifers. the reactions of elongation and desaturation from the C18:2n-6 and C18:1n-9 seemed to be much more important in the larvae. Lastly, the transition from a diet based on rotifers to one made up exclusively of frozen Artemia nauplii led to a significant reduction of fatty acids in fish. It reached 60.2% and 26.5% of the total fatty acids in the gudgeon and perch, respectively, and was observed especially at the level of the PUFA. On the other hand, a slight increase of the ratio n-3/n-6 was pointed out in the perch fed a mixed diet (co-feeding with rotifers and dry food), a phenomenon probably due to the reduction of C18:2n-6 in the larvae.     

Effect of different enrichment products rich in docosahexaenoic acid on growth and survival of meagre,Argyrosomus regius (Asso, 1801)

Live prey used in aquaculture to feed marine larval fish – rotifer and Artemia nauplii – lack the necessary levels of n‐3 polyunsaturated fatty acids (n‐3 PUFA) which are considered essential for the development of fish larvae. Due to the high voracity, visual feeding in conditions of relatively high luminosity, and cannibalism observed in meagre larvae, a study of its nutritional requirements is needed. In this study, the effect of different enrichment products with different docosahexaenoic acid (DHA) concentrations used to enrich rotifers and Artemia metanauplii have been tested on growth, survival, and lipid composition of the larvae of meagre. The larvae fed live prey enriched with Algamac 3050 (AG) showed a significantly higher growth than the rest of the groups at the end of the larval rearing, while the larvae fed preys enriched with Multigain (MG) had a higher survival rate. DHA levels in larvae fed prey enriched with MG were significantly higher than in those fed AG‐enriched prey. High levels of DHA in Artemia metanauplii must be used to achieve optimal growth and survival of meagre larvae.     

Examination of a practical method for copper enrichment of euryhaline rotifers (Brachionus plicatilis) as diet of Eriocheir sinensis zoea larvae

In this study, an effective method to enrich the rotifer Brachionus plicatilis with copper was developed as a feed for the Chinese mitten crab Eriocheir sinensis zoea larvae. Changes in the concentrations of other minerals in rotifers were also examined when copper was added for rotifer enrichment. The ability of Chlorella to absorb waterborne copper is much higher than that of rotifers, and hence, copper was preaccumulated in Chlorella before its ingestion by rotifers. The copper content in rotifers was comparable to the dietary copper requirement of the crab larvae when the rotifers were enriched with 0.1 mg Cu g⁻¹ Chlorella for 12 h. Further enrichment in rotifers with Cu‐enriched Chlorella and lipid emulsions did not significantly change the profile of major fatty acids and mineral composition in the rotifers. Evidence shows the feasibility of copper enrichment in rotifers using microalgae that can accumulate copper. This study indicates that copper in rotifers can be enriched by feeding copper‐enriched algae at a concentration of 0.1–0.2 mg Cu g⁻¹ Chlorella. The developmental rates of E. sinensis can be improved by feeding zoea larvae with copper‐enriched rotifers, but survival rates were not affected by dietary copper enrichment.     

Effect of light irradiation on dynamics of vitamin A compounds in rotifers and Artemia

ABSTRACT:   The dynamics of vitamin A (VA) compounds in live food during enrichment were examined under different light conditions. Rotifers Brachionus plicatilis and Artemia nauplii ( Artemia ) were enriched with or without 10 mg VA palmitate (VAp) in 1 L of culture medium for 24 h under either bright (2000 lx), or dark (<1 lx) conditions. VAp, retinol (ROH), retinal (RAL) and retinoic acid (RA) contents were analyzed at 0 h (before enrichment) and at 3, 6, 12, 18 and 24 h after the onset of enrichment. Retinoid content in rotifers enriched in darkness was always higher than that enriched under light. VAp content showed two peaks at 3 and 18 h in rotifers enriched in darkness, but it showed one peak at 3 h in rotifers enriched under light. ROH and RA contents increased over the 24-h period in rotifers enriched in darkness, whereas they decreased 12 h onward in rotifers enriched under light. In Artemia , VAp and ROH contents were always higher than when enriched under the bright condition, but their dynamics showed a similar pattern in Artemia enriched under dark and bright conditions.