Some effects of early starvation on the survival and development of barnacle nauplii,Balanus improvisus (Darwin)

Newly hatched stage I–II nauplii of Balanus improvisus (Darwin) were “totally starved” (until death) or “partially starved” for the first 48 h and 96 h of their development. Daily mortality and molting were monitored throughout larval development in both starved and fed control groups. Fed control animals exhibited a largely synchronous molting pattern with instars of equal duration. Total starvation suppressed molting beyond stage II; 50% mortality occurred in ≈4 days at both 15 and 21 °C, while longest survival time was 7 days at 15 °C and 6 days at 21 °C. At 15 °C, partially starved nauplii retained the ability to complete naupliar development but at a slower overall rate and with increased mortality relative to controls. These effects were more pronounced in the 96-h group. Increased mortality of stage VI nauplii was evident in both partially starved groups (7.1% for 48 h, 18.8% for 96 h) relative to unstarved controls (3.1%). Stage II nauplii exhibited little resistance to starvation and survival potential may have decreased as soon as 24 h.     

Caloric content of larvae of the brine shrimpArtemia salina

Summary 1. Caloric contents ofArtemia salina nauplii and larvae have been determined by employing a combustion calorimetry. Freshly hatched nauplii contain on an average 5953 cal/g organic substance; the respective value for 7-day-old (2 mm long) larvae is 5854 cal/g.2. The effect of starvation on the caloric contents was investigated. After a 72 hour starvation period, nauplii contain 5430 cal/g organic substance, 2 mm long larvae 5115 cal/g.3. The ash contents (expressed as % of body dry weight) ofArtemia larvae increase as a function of the length of the starvation period.4. After determining the weight of the nauplii, the caloric content of a single nauplius was calculated after different periods of starvation. It ranges from 0.00924 cal per freshly hatched nauplius to 0.00459 cal per nauplius starved for 96 hours.

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Kaloriengehalt von Larven des SalinenkrebsesArtemia salina

Kurzfassung Der Energiegehalt frisch geschlüpfter Nauplien (5953 cal/g organische Substanz) und 2 mm langer Larven (Metanauplius IV, 5854 cal/g organische Substanz) vonArtemia salina Leach wurde mit einem Parr 1412 Bombenkalorimeter ermittelt. Ferner wurde der Einfluß verschieden langer Hungerperioden auf den Kaloriengehalt dieser Tiere untersucht. Nach 72stündigem Hungern wurden für die Nauplien 5430 cal/g organische Substanz und für die 2 mm langen Larven 5115 cal/g organische Substanz ermittelt. Der Aschegehalt der Tiere stieg mit zunehmender Dauer der Hungerperiode. Anhand des Gewichts der geschlüpften und hungernden Nauplien wurde der Kaloriengehalt einzelner Tiere bestimmt: er reicht von 0,00924 cal pro Tier (gerade geschlüpfter Nauplius) bis 0,00459 cal pro Tier (Nauplius, 96 Stunden ohne Futter).

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Dedicated to Professor Dr.Friedrich Krüger on his 65^th birthday, August 18, 1967.     

Diet-induced variations in fatty acid content and composition of two on-grown stages of Artemia Salina

Three species of microalgae, the freshwater Euglena gracilis and themarine Dunaliella salina and Tetraselmis suecica, were fed tothe brine shrimp Artemia salina in order to compare their suitabilityin terms of fatty acid enrichment, and their effect on the biometric parametersof the zooplankter. The fatty acid content and composition were analyzed for the post-larval and pre-adult stages of Artemia fed the algae and theresults compared to the initial content of unfed 24-hour post-hatch nauplii.Differences in the total fatty acid content occurred between the three stages,the fatty acid profile being determined by the composition of the diet. A decreasing trend for almost all the individual fatty acids occurred throughdevelopment from post-larva to pre-adult with each of the three algal diets.Biometrical differences between Artemia fed the marine algae and that fed Euglena were not consistent in the post-larval stage, but became considerable in the pre-adult stage. Artemia fed with Euglena achieved twice the weight of animals fed the marine algae and showed thehighest length. The implications for the use of on-grown Artemia as afeed in larviculture of marine and freshwater fish and crustaceans are considered.     

Effect of varying levels of dietary essential fatty acid during early ontogeny of the sea scallop Placopecten magellanicus

This study investigated the biological effects of various dietary essential fatty acids levels to sea scallop larvae, Placopecten magellanicus. Scallop larvae were fed three diets from D-veliger to settlement. Diet A consisted of Isochrysis sp. and Pavlova lutheri, diet B was a mix of Isochrysis sp. and Chaetoceros muelleri and diet C consisted of the same two species, but C. muelleri was grown under silicate deprivation to alter the fatty acid composition. Pediveligers (28 days old) were sampled prior to settlement for fatty acid analysis, growth measurement and survival assessment. Survival and settlement success were measured at the end of the experiment (day 40). Our results show that feeding regime greatly influenced larval size, settlement and fatty acid composition. Diet A was severely deficient in arachidonic acid (20:4n-6, AA), leading to the poorest larval growth, survival and lipid content. Nevertheless, larvae fed diet A selectively accumulate AA by a factor three compared to the dietary amount. Shell size of 28-day-old larvae was positively correlated with AA content and negatively correlated with eicosapentaenoic acid (20:5n-3, EPA)-AA ratio, thus suggesting that these two variables are of major interest for the optimisation of larval growth in sea scallops. Finally, larvae fed diet C displayed 20% higher shell size at day 28 than larvae fed diet A and B, likely in relation to the dietary amount of saturated fatty acid (SFA). However, the moderate survival and settlement success of these groups of larvae might be associated with a relative deficiency in docosahexaenoic acid (22:6n-3, DHA). This study underlines that the overall balance between polyunsaturated fatty acid (PUFA) needs to be considered to adequately fed sea scallop larvae.     

Response of bighead carp Aristichthys nobilis and Asian catfish Clarias macrocephalus larvae to free-living nematode Panagrellus redivivus as alternative feed

The use of Panagrellus redivivus as live feed for bighead carp and Asian catfish larvae was tested. In experiment 1, carp larvae were given Artemia nauplii (control) or Panagrellus twice daily for 21 days. A third treatment consisted of unfed larvae. The same three treatments were used in experiment 2 plus another with a commercial entomopathogenic nematode (EPN). Bighead carp larvae given Panagrellus in experiment 1 had much lower growth and survival than those fed Artemia nauplii. This could be due to low nematode density (5–30 mL^?1 water) during feeding. The unfed larvae had 100% mortality by days 11–13. In experiment 2, growth and survival of carp larvae given Artemia nauplii (5–10 mL^?1) and Panagrellus (50 mL^?1) did not differ significantly (P > 0.05). All unfed larvae had died by day 13, while larvae fed EPN were all dead by day 8. Two experiments on Asian catfish were likewise conducted. In experiment 1, the catfish larvae were fed Tubifex (ad libitum), Panagrellus (50–100 mL^?1 per feeding) orArtemia (5 nauplii mL^?1 per feeding) three times daily for 14 days. In experiment 2, larvae were fed Artemia alone (10 nauplii mL^?1 per feeding), Panagrellus alone (100 mL^?1 per feeding), or their combination with a 38% protein dry diet twice daily. For both experiments, catfish larvae fed Panagrellus had significantly lower growth and survival than those fed Tubifex or Artemia. The combination of Panagrellus and dry diet created little improvement in the growth and survival of catfish larvae.     

Schinus terebinthifolius Leaf Extract Causes Midgut Damage,Interfering with Survival and Development of Aedes aegypti Larvae

In this study, a leaf extract from Schinus terebinthifolius was evaluated for effects on survival, development, and midgut of A. aegypti fourth instar larvae (L4), as well as for toxic effect on Artemia salina. Leaf extract was obtained using 0.15 M NaCl and evaluated for phytochemical composition and lectin activity. Early L4 larvae were incubated with the extract (0.3–1.35%, w/v) for 8 days, in presence or absence of food. Polymeric proanthocyanidins, hydrolysable tannins, heterosid and aglycone flavonoids, cinnamic acid derivatives, traces of steroids, and lectin activity were detected in the extract, which killed the larvae at an LC₅₀ of 0.62% (unfed larvae) and 1.03% (fed larvae). Further, the larvae incubated with the extract reacted by eliminating the gut content. No larvae reached the pupal stage in treatments at concentrations between 0.5% and 1.35%, while in the control (fed larvae), 61.7% of individuals emerged as adults. The extract (1.0%) promoted intense disorganization of larval midgut epithelium, including deformation and hypertrophy of cells, disruption of microvilli, and vacuolization of cytoplasms, affecting digestive, enteroendocrine, regenerative, and proliferating cells. In addition, cells with fragmented DNA were observed. Separation of extract components by solid phase extraction revealed that cinnamic acid derivatives and flavonoids are involved in larvicidal effect of the extract, being the first most efficient in a short time after larvae treatment. The lectin present in the extract was isolated, but did not show deleterious effects on larvae. The extract and cinnamic acid derivatives were toxic to A. salina nauplii, while the flavonoids showed low toxicity. S. terebinthifolius leaf extract caused damage to the midgut of A. aegypti larvae, interfering with survival and development. The larvicidal effect of the extract can be attributed to cinnamic acid derivatives and flavonoids. The data obtained using A. salina indicates that caution should be used when employing this extract as a larvicidal agent.     

Protists and detrital particles as prey for the first larval stage of the brachyuran crab, Hemigrapsus oregonensis

Newly-hatched larvae of the brachyuran crab, Hemigrapsus oregonensis, were raised in the laboratory on an autotrophic dinoflagellate (Prorocentrum micans), a heterotrophic dinoflagellate (Noctiluca milaris), a green alga (Dunaliella tertiolecta), an unfed control, and a fed control of Artemia sp. nauplii. Larvae also were fed preparations of seagrass detritus that had been cultured both to promote microbial colonization and to discourage it. Detrital diets were used both alone and in combination with sub-optimal applications of Artemia sp. nauplii. Larvae raised on P. micans showed survival to zoeal stage II equal to those raised on the Artemia sp. nauplii control, although development was delayed. Larvae raised on N. milaris showed substantial (34.7%) survival to zoeal stage II; however survival was lower and development slower than for Artemia sp. nauplii-fed larvae. Survival on D. tertiolecta was less than 3%. Larvae fed microbially-enriched detritus showed a delay in mortality as compared to unfed controls. No larvae fed solely on detritus survived to zoeal stage II. When larvae were fed a sub-optimal diet of Artemia nauplii, supplemented by detrital particles, survival to zoeal stage II increased, although not to the level shown by Artemia-fed larvae in optimal application. Development was not accelerated over the sub-optimal diet in either treatment. The potential for larval crabs to utilize a wide variety of potential prey immediately upon hatching is significant given their susceptibility to early starvation. Such omnivory also suggests a trophic link between carbon sources of the microbial loop and crab larvae.     

The impact of food type, temperature and starvation on larval development of Balanus amphitrite Darwin (Cirripedia: Thoracica)

The impact of diatom food species (Chaetoceros calcitrans and Skeletonema costatum), temperature and starvation on the larval development of Balanus amphitrite was evaluated. Starvation threshold levels for different ages of larvae (0- to 5-day-old) fed with C. calcitrans and S. costatum and then starved at 5, 15 and 25 °C temperature were estimated as ultimate recovery hour (URH; denoting the starvation point in hours at the end of which larvae can recover and continue development). Effect of temperature on starvation threshold varied significantly with larval age and food species. The URH declined with larval age at 5 °C, but not at 15 and 25 °C. The URH and grazing rates were high for early instars fed on C. calcitrans, and for advanced instars fed on S. costatum. Carbon gain through feeding was maximum for 2-day-old larvae when fed with C. calcitrans and decreased with larval age. However, when fed with S. costatum carbon gain increased with larval age. This confirms that with development the utility of food types changes. The differences in the carbon gain can be attributed to differences in grazing rate due to variations in the size of the diatom cells, larval intersetular distance, diatom sinking rate and the photo-taxic behavior of larvae. Molting was observed at times when larvae were undergoing starvation and this could be viewed as stress-induced molting, and it differed with the larval age and food organisms.     

Lipid content and fatty acid composition of larvae and adults of the velvetbean caterpillar, Anticarsia gemmatalis, as affected by larval diet

Eight fatty acids were found in the food, larvae and adults of the velvetbean caterpillar, Anticarsia gemmatalis, with C16:0, C18:0, C18:1, C18:2 and C18:3 accounting for over 90% of the total. Fatty acid composition of the larvae tended to reflect that of their food. The most striking differences were the high percentages of C18:1 and C18:2 and the low percentage of C18:3 in the artificial diet and artificial diet-reared larvae compared to the foliage of three species of legume food plants (soybean, Glycine max; pigeon pea, Cajanus cajan; and hairy indigo, Indigofera hirsuta) and foliage-reared larvae. Lipid content (%dw) declined during metamorphosis from mature larva to adult with diet-reared larvae and adults exhibiting significantly higher lipid contents than foliage-reared insects. Regardless of larval food, newly eclosed adults tended to exhibit a decrease in the % of C18:3, and increases in C16:0 and C18:1 compared to larvae. Larval diet clearly influenced the fatty acid composition of larvae and adults, but only the % of C18:2 did not change between food, larvae and adults.     

Growth and survival of river catfish Mystus nemurus (Cuvier & Valenciennes) larvae fed isocaloric diets with different protein levels during weaning

The growth of river catfish Mystus nemurus (Cuvier & Valenciennes) larvae fed four isocaloric diets (4200 kcal kg^?1) with different protein levels during weaning was determined. Diets containing 45, 50, 55, and 60% protein were formulated by linear programming using amino acid profiles based on that of 2‐day‐old river catfish larvae. Artificial diets were fed to the larvae beginning at day 5 after being initially fed Artemia nauplii for 4 days. The larvae thrived solely on artificial diets from day 8 to day 16. On the other hand, the control larvae were fed Artemia nauplii from day 1 to day 16. Results of the feeding trial showed that growth and survival of M. nemurus larvae given the diet containing 60% protein were high and comparable to those of the larvae given only live food (control). Larvae fed the 55% protein diet had significantly lower growth and survival than the larvae on the control and 60% diets but significantly higher growth and survival rates than did larvae fed with 45 and 50% protein diets. Carcass moisture and total lipids after 16 days of feeding did not differ significantly (P > 0.05), but body protein increased with increasing dietary protein. Body protein of the control larvae was similar to that of larvae given the 60% protein diet.     

LC–MS/MS-Based Metabolome Analysis of Biochemical Pathways Altered by Food Limitation in Larvae of Ivory Shell, <Emphasis Type="Italic">Babylonia areolata</Emphasis>

Ivory shell, Babylonia areolata, is one of the commercially important mariculture species in China and South East Asia. Survival varies in the artificial hatching and larval rearing of B. areolata. Food deprivation may be involved in rearing mortality, and so, a better understanding of how larvae respond and adjust to starvation is needed. In this study, the metabolite profiles of newly hatched larvae with yolk (I), larvae with yolk exhaustion (II), larvae suffering 24 h starvation after yolk exhaustion (III), and larvae fed with exogenous nutrients after yolk exhaustion (IV) were analyzed by LC–MS/MS. Principal component and cluster analyses revealed differential abundance of metabolite profiles across groups. When compared to metabolite levels of the I group, significantly up-regulated metabolites included polyunsaturated fatty acids, phospholipids, nucleotide, amino acids, and their derivatives were found in the II group, indicating that organisms relied predominantly on glycerophospolipid metabolism and protein-based catabolism for energy production during this stage. During starvation after yolk exhaustion, the levels of all energy related metabolites were significantly reduced, but an increase in products of purine and pyrimidine metabolism indicated an insufficient energy supply and an increase in cellular disintegration. Larvae fed exogenous nutrients can have significantly improved metabolism compared to starved larvae. These findings suggest that metabolomics, using LC–MS/MS, can be used to assess the physiological status and food-affected metabolic changes affecting B. areolata larvae.     

Growth response of African catfish,Clarias gariepinus (B.), larvae and fingerlings fed protease‐incorporated diets

African catfish, Clarias gariepinus (B.), is one of the promising freshwater fish species in African aquaculture but the expansion of its farming needs more production of its larvae. The use of live food organisms at first feeding for larvae is still obligatory. That increases the cost of larvae production. Hence, the incorporating of exogenous enzymes especially protease in artificial microdiets may provide affordable alternatives for enhancing the larvae performance. The present study was carried out to evaluate the growth and survival of larvae or fingerlings of African catfish fed artificial diets incorporated with different protease levels. Four artificial diets were formulated and enriched with protease enzyme at levels of 0.0, 750, 1,000, and 1,250 unit/kg diet; after that diets were made into crumbles (100–200 µm diameter). After absorption of the yolk sac, diets were offered to fish larvae (3.6 ± 0.2 mg) in triplicates as a starter feed up to apparent satiation every two hours for 30 days. In another treatment, fish larvae were fed on newly hatched Artemia nauplii (2,500 Artemia/L) as a starter food. In another experiment, African catfish fingerlings (10.1 ± 1.6 g) were fed on the same diets up to satiation twice a day for 2 months. It was noticed that the dietary protease improved larval growth and survival but not as Artemia nauplii did where fish larvae fed on Artemia nauplii showed highest growth and survival followed by those fed a diet enriched with 1,250 unit/kg diet of protease. The mortality of larvae fed protease‐enriched diets as well as the control diet was occurred mostly at the first week reaching its maximum at the third week. The poor growth was observed with fish larvae fed the control diet. Meanwhile, catfish fingerlings fed protease‐enriched diets showed higher growth over those fed the control diet. The larvae survival (11.0%–41.7%) was enhanced by increasing protease levels and it was lower than that of fingerlings (95.6%–100.0%). Furthermore, protein retention and digestibility were significantly improved with protease supplementation over the control diet especially at a level of 1,000 unit/kg diet. As compared with the previous studies, live food should be used in larvae rearing for the first week after that a starter diet enriched with protease at levels of 1,250 unit/kg diet should be used. In case of fish fingerlings, the dry diets should be enriched with 1,100 unit/kg diet to improve diet digestibility and subsequently enhance their growth.     

Feeding by an omnivorous planktonic copepod aetideus divergens Bradford

Aetideus divergens Bradford is representative of a large group of marine planktonic calanoid copepods which are omnivores or mixed feeders. Because very little quantitative information is available on the feeding behavior of these copepods, laboratory feeding experiments have been carried out with adult female A. divergens presented with various sizes and concentrations of diatoms and freshly hatched nauplii of Artemia. The copepod fed most efficiently on the largest size of diatom and on Artemia nauplii, but was peculiarly inefficient at feeding on small diatoms, even when they were available at very high concentrations. In this respect, the copepod differs from filterfeeding copepods, such as Calanus pacificus Brodsky. A possible explanation of this difference depends upon Aetideus being less capable of handling very small food particles than Calanus. Aetideus divergens and its congeners usually occur at subsurface depths not far below the mixed layer and seem to be adapted for feeding on large particles, possibly large phytoplanktonic organisms and fecal pellets, which sink out of the mixed layer.     

Suitability of monotypic and mixed diets for Anopheles hermsi larval development

The developmental time and survival to eclosion of Anopheles hermsi Barr & Guptavanij fed monotypic and mixed diets of ten food types were examined in laboratory studies. Larvae fed monotypic diets containing animal detritus (freeze‐dried rotifers, freeze‐dried Daphnia pulicaria, and TetraMin® fish food flakes) and the mixotrophic protistan Cryptomonas ovata developed faster and survived better than larvae that were fed other monotypic diets. Survival to adulthood of larvae fed several concentrations of the diatom Planothidium (=Achnanthes) lanceolatum was poor (<13%) and larval development time was approximately twice that of larvae fed TetraMin® fish food flakes, the standard laboratory diet. Larvae fed monotypic diets containing prokaryotes (bacteria [Bacillus cereus] and cyanobacteria [Oscillatoria prolifera]) and brewer's yeast (Saccharomyces cerevisiae) failed to survive beyond the 1^st and 2^nd instar, respectively. Larvae fed only chlorophytes, single‐celled Chlamydomonas reinhardtii and filamentous Spirogyra communis, failed to complete larval development, regardless of the concentration tested. Cohorts fed a combination of food types (mixed diets) usually developed better than cohorts fed monotypic diets. Food types that failed to support complete development when fed alone often facilitated development to adulthood when fed in combination with food types containing >1% C₂₀ polyunsaturated fatty acids as total fat, but regardless of essential fatty acid content, algae that produced mucilage and filaments that sank out of the feeding zone were poor quality diets.     

The effect of starvation and starvation followed by feeding on enzyme activity and the metabolism of [U-14C]glucose in liver from growing chicks

1. The conversion of [U-(14)C]glucose into carbon dioxide, cholesterol and fatty acids in liver slices and the activities of ;malic' enzyme, citrate-cleavage enzyme, NADP-linked isocitrate dehydrogenase and hexose monophosphate-shunt dehydrogenases in the soluble fraction of homogenates of liver were measured in chicks that were starved or starved then fed. 2. In newly hatched chicks the incorporation of [U-(14)C]glucose and the activity of ;malic' enzyme did not increase unless the birds were fed. The response to feeding of [U-(14)C]glucose incorporation into fatty acids increased as the starved chicks grew older. 3. Citrate-cleavage enzyme activity increased slowly even when the newly hatched chicks were unfed. On feeding, citrate-cleavage enzyme activity increased at a much faster rate. 4. In normally fed 20-day-old chicks starvation decreased the incorporation of [U-(14)C]glucose into all three end products and depressed the activities of ;malic' enzyme and citrate-cleavage enzyme. Re-feeding increased all of these processes to normal or higher-than-normal levels. 5. In both newly hatched and 20-day-old chicks starvation increased the activity of isocitrate dehydrogenase and feeding or re-feeding decreased it. 6. Very little change in hexose monophosphate-shunt dehydrogenase activity was observed during the dietary manipulations. 7. The results indicate that increased substrate delivery to the liver is the principal stimulus to the increased rate of glucose metabolism observed in newly hatched chicks. The results also suggest that changes in the activities of ;malic' enzyme and citrate-cleavage enzyme are secondary to an increased flow of metabolites through the glucose-to-fatty acid pathway and that the dehydrogenases of the hexose monophosphate shunt play a minor role in NADPH production for fatty acid synthesis.     

Experiments for the improved use of decapsulated Artemia cysts in intensive culture of African catfish larvae

Feeding dried and vitamin C enriched decapsulated Artemia cysts to African catfish larvae increased their growth rate significantly after 6 days over those fed only freshly decapulated cysts. Groups fed with Artemia nauplii had a significantly higher growth during the experiment, although this difference was not considerably important in practice. Tank colour had no influence on growth. Because of their lower price, the decapsulation of lower quality cysts can be an appropriate feed source in intensive cultures of African catfish larvae.     

The reproduction strategy of oyster ostrea edulis L. from the biochemical point of view

• 1.1. Influence of the biochemical composition of food (four species of micro-algae and one mixture) on the biochemical composition of gonads and larvae of O. edulis (total protein, lipid, carbohydrate, ash content, neutral and polar lipid class composition, amino acid composition and fatty acid composition of total, neutral and polar lipids) and the size of newly released larvae have been investigated.
• 2.2. Precentage of total lipids and triacylglycerols in gonads depends on that in algae (r = 0.52 and 0.69 accordingly).
• 3.3. Gonads rich in lipids had a higher level of triacylglycerols, phospholipids, polar lipids and a lower value of the ratio phosphatidylethanolamine/phosphatidylcholine (PE/PC) than gonads with a low lipid content.
• 4.4. Amino acid composition of gonads depends on that of food, in this case, essential acids are preferentially accumulated (Asp acid, Ser, Ala, Cys, Tyr and Pro) and two non-essential (Thr and Lys).
• 5.5. Fatty acid composition of total lipids of gonads was rather stable; except for the two essential acids 20:523 and 22:6w3, their percentage depends on that of food r = 0.65 and 0.65 accordingly). Fatty acid composition of neutral lipids was more diverse (in number and degree of variety) as compared to polar lipids.
• 6.6. Larvae released from oysters with gonads rich in lipids had a higher percentage of lipids, triacylglycerols, size and a lower ash percentage and value of ratio PE/PC, as compared to larvae from gonads with low lipid content. Total lipid and triacylglycerol contents in gonads correlate rather well with those in larvae (r = 0.77 and 0.47 accordingly).
• 7.7. Phospholipid class composition of larvae strongly depends on that of gonads. All the correlations are high and positive in character (except for phosphatidylinositol).
• 8.8. Amino acid composition of larvae depends on that of gonads and, as in the case with gonads, the same essential acids are accumulated in the first place.
• 9.9. Fatty acid composition of total lipids of newly released larvae was rather stable and independent on that of gonads except for total polyunsaturated acids (r = 0.70) and 20:5w3 (r = 0.65). Fatty acid composition of neutral lipids was lesser diverse (in number and degree of variation) as compared to polar lipids.

     

Larval rearing of chub, Leuciscus cephalus (L.), using decapsulated Artemia as direct food

Little is known about the larviculture of the chub, Leuciscus cephalus (L.), an endangered cyprinid species endemic to European flowing waters. The use of decapsulated Artemia cysts as food for chub larviculture was investigated. After 3‐day feeding with the rotifer Brachionus calyciflorus, the larvae were fed on different diets: (i) dried decapsulated Artemia cysts, (ii) Artemia nauplii, (iii) rotifers for seven more days and then Daphnia collected from a pond, and (iv) an artificial diet. After a 24‐day rearing period, the highest survival rate was obtained with the larvae receiving decapsulated Artemia cysts. Feeding of the larvae with an artificial diet resulted in a significantly lower survival rate compared with the other groups. At the end of the experiment, the larvae fed on Artemia nauplii yielded a significantly higher mean length compared with the other groups. Feeding an artificial diet resulted in a significantly lower average weight and mean length gain compared with the other groups.     

Effects of feeding,starvation, and refeeding on the fatty acid composition of channel catfish,ICtalurus punctatus,tissues

• 1.1. The effects of feeding, food deprivation (14 and 28 days) and refeeding (starved 14 then fed 14 days) on the fatty acid composition of white muscle, liver and brain of pond-raised channel catfish (Ictalurus punctatus) were investigated.
• 2.2. Levels of n-3 fatty acids were significantly higher (P < 0.05) in white muscle of fish starved 28 days (10.7%) than in fish fed throughout the study (8.0%), due primarily to an increase in 22:6(n-3) docosahexaenoic acid or DHA.
• 3.3. Significantly higher levels of 20:5(n-3) (eicosapentaenoic acid or EPA) were found in livers offish starved 28 days (P < 0.05) compared to fish fed throughout the study.
• 4.4. Results suggest that the fatty acid compositions of channel catfish white muscle and liver are subject to only limited perturbation during periods of starvation and refeeding and that the brain is extremely well protected.

     

Temperature and laboratory feeding rates in Carcinusmaenas L. (Decapoda: Portunidae) larvae from hatching through metamorphosis

Larvae of Carcinus maenas L. were reared in the laboratory and temperature-dependent stage durations of successive instars were examined at 12, 15, 18, and 25°C. Feeding rates (FR), in numbers of newly hatched Artemia nauplii, biomass, and energy consumed by a single crab larva during 24 h, were measured daily through the moulting cycles of all larval stages at the four temperatures. Dry weight (DW) and elemental content of carbon (C), nitrogen (N) and hydrogen (H) were analysed in newly hatched (0 h) and 1-day-old (24 h) Artemia nauplii at six temperatures (6, 9, 12, 15, 18, 25°C). Due to a 24 h feeding regime, the temperature dependent “mean nutritive value” of newly hatched brine shrimp nauplii is defined, individual biomass (DW, C, N, H) and energy (Joule) 12 h after hatching. General figures in changing individual daily FR, and temperature-dependent peculiarities are discussed. The total amount of food ingested by successive larval instars increases exponentially, while the increasing cumulative quantity consumed by individual crab larvae on successive days of development is described by power functions. At higher temperatures significantly less absolute biomass and energy is consumed during the entire larval development. C. maenas megalops are the main energy consumers in larval life, contributing 41 to 67% (12 to 25°C) to the total larval energy intake between hatching and metamorphosis. Larval ability to adapt to increasing metabolic costs for maintenance in higher water temperatures is discussed with average daily feeding rates (AFR). Improved efficiencies are presented for the cumulative larval energy budget, 31% in assimilation, and 4.4% in gross growth (K₁).