Artificial spawning of carp, Cyprinus carpio (L.)

The effect of reproduction was investigated on females of Hungarian strain W, French strain F, and their cross‐breed 1X whose ovulation was stimulated with carp pituitary (0.3 mg kg^?1and, after 12 h, 2.7 mg kg^?1) or Ovopel (one‐fifth of a pellet per kg and, after 12 h, one pellet per kg). It was found that in the case of Ovopel treatment, the percentage of spawning females of strain F and the cross‐breed 1X was higher than in the hypophysed fish compared. The applied ovulation stimulators did not significantly affect the weight of obtained eggs, whereas the significant (P ≤ 0.01) effect was recorded with respect to the quality of eggs after 12‐, 24‐, 36‐ and 48‐h of incubation. After Ovopel stimulation, the quality of eggs was better. The origin of the females had no statistically significant effect on the weight of eggs although the yield of eggs from fish of strain W was much smaller than that from females of strain F and the 1X cross‐breed. The interaction between the ovulation stimulator and the provenance of the females was significant (P ≤ 0.05) for the percentage of live embryos after 48‐h of incubation of eggs. Eggs of the best quality (and highest weight) were obtained from fish of strain F and cross‐breed 1X treated with Ovopel. In females of strain F that spawned within 6 and 10 h after the second Ovopel injection, the effect of the ovulation time on the weight of eggs was non‐significant. It was significant with respect to the percentage of egg fertilization and of live embryos after 36‐h of incubation (P ≤ 0.01 and P ≤ 0.05 respectively). The better quality of eggs (and their higher weight) was recorded when this time was shorter.     

Induction of Out-of-Season Spawning of Pikeperch, Sander Lucioperca (L.)

Pikeperch were induced to spawn 3 months prior to the natural spawning period through photothermal and hormonal stimulation. Females (five specimens in each group) were stimulated with injection of human chorionic gonadotropin (hCG) once (200 IU kg^–1), twice (200 IU kg^–1, second dose after 48 h–400 IU kg^–1) or three times (200 IU kg^–1, after 24 h–200 IU kg^–1 and after another 24 h–200 IU kg^–1). The control group was injected once with 0.9% NaCl. The males were stimulated with a single hormone dose of 200 IU kg^–1. Eggs were obtained from all the hormonally treated fish. None of the control group females, which were only stimulated photothermally, ovulated any eggs. The time of ovulation was 66–71 h following the first injection, and the eggs viability until the eyed stage (from 71.5 to 77.5%) did not depend on the number of hormone doses (P > 0.05). The out-of-season spawning method described in this paper could be used to provide pikeperch larvae for intensive culture systems (recirculating water systems) before natural spawning season and to produce larger-sized pikeperch fingerlings for stocking.     

Artificial spawning of female Lithuanian strain B carp (Cyprinus carpio L.) after treatment with carp pituitary homogenate, Ovopel or [d-Tle6, ProNHEt9] GnRH-a (Lecirelin)

The results of reproduction of females from Lithuanian strain B carp after ovulation stimulation with carp pituitary homogenate (CPH; 0.3+2.7 mg kg^?1; group I), Ovopel (1/5+1 pellet kg^?1; group II) or [d ‐Tle⁶, ProNHEt⁹] GnRH‐a (Lecirelin) with metoclopramide (15 μg kg^?1+10 mg kg^?1 respectively; group III) were investigated. The lowest percentage of spawning females (71%) was recorded in the group treated with CPH. In case of Ovopel or Lecirelin induced ovulation, 86% of females spawned. No statistically significant effect of the ovulation stimulator (group) on the weight of eggs was found; however, the highest mean weight of eggs (expressed both in grams and in the percentage of female body weight) was recorded for the group treated with Ovopel (1400 g and 13%). After the treatment with CPH or Lecirelin, the weight of eggs was 1140 g (11%) and 1100 g (10%) respectively. The ovulation stimulator significantly affected the percentage of live embryos after 36 and 48 h incubation of eggs (P≤0.05; P≤0.01). After treatment with [d ‐Tle⁶, ProNHEt⁹] GnRH‐a, eggs of the best quality were obtained and after 36 and 48 h incubation the mean percentages of live embryos were significantly higher than the means calculated for the remaining two groups. No statistically significant differences were found between the percentage of living embryos after 36 and 48 h incubation of groups I and II.     

Dehydration is more effective for the control of embryonic development and larval hatching of Diplectanum aequans (Monogenea, Diplectanidae) than formalin and trichlorphon

Embryonic development and larval hatching of the monogenean Diplectanum aequans, gill parasite of sea bass Dicentrarchus labrax, was studied in relation to different prophylactic treatments. Groups of eggs of D. aequans were submitted to different in vitro treatments: formalin (300 and 100 L L^–1 per 1 hour), Neguvon^® (trichlorphon 0.2 mg L^–1 per 48 hours) and dehydration for 4 and 8 hours. Percentages of hatched larvae, aborted larvae and undeveloped embryos were estimated in comparison with the control group. Results showed that 300 L L^–1 formalin and dehydration treatments were able to reduce larval hatching significantly, while Neguvon^® and 100 L L^–1 formalin treatments had no effect.     

Artificial spawning of African catfish Heterobranchus longifilis: differences between the effects on reproduction in females treated with carp pituitary homogenate or Ovopel

The effects of the controlled reproduction of African catfish Heterobranchus longifilis after ovulation stimulation with carp pituitary homogenate (CPH; 4 mg kg^?1; group I) or Ovopel (1/5+1 pellet kg^?1; group II) were investigated. After the application of Ovopel, eggs were obtained from a higher percentage of females than after a CPH treatment (87.5% and 75.0% respectively). The statistically significant (P≤0.05) effect of ovulation stimulator was specified only in the case of the weight of eggs (expressed in grams and in percentage of female body weight), being higher in fish treated with Ovopel compared with CPH‐treated fish (176.02 g, 8.43% and 109.51 g, 5.48%). The quality of eggs expressed in percentage of live embryos after 24 h incubation was higher by 7.5% in fish treated with Ovopel. Latency period did not significantly affect the weight of eggs, fertilization percentage or percentage of living embryos after 24 h of egg incubation. However, the weight of eggs and percentage of living embryos after 24 h incubation were higher in fish spawning after 12 h latency (159.38 g and 85.30%) compared with the weight and quality of eggs obtained from females spawning after 14 h latency (126.15 g and 76.04%).     

Response of a Juvenile Cyprinid,Lake Minnow <Emphasis Type="Italic">Eupallasella perenurus</Emphasis> (Pallas), to Different Diets

Three commercial starters (Carp Starter, Uni Starter and Perla Plus) and one non-commercial, with frozen Chironomidae larvae as a reference diet, were evaluated for the intensive rearing of juvenile lake minnow Eupallasella perenurus, a cyprinid fish that is critically endangered in Poland. The growth, condition, survival, body deformities, and chemical body composition were studied. The 90-day laboratory experiment was performed at 22 °C with fish that were initially 24.6 mm (mean total lenth (TL)) and 0.11 g (mean body weight (BW)). Satisfactory fish growth was attained with all of the diets; however, the largest (p ≤ 0.05) final size (48.5 mm TL, 1.55 g BW) and the lowest condition coefficient (K = 1.34) were noted in fish fed the non-commercial starter. The final survival rates were very high (97.5–100%). Skeletal deformities (in 74 to 92% fish) were recorded exclusively in fish fed commercial starters. All commercial starters resulted in considerably higher lipid content and lower ash content than did the non-commercial starter and the reference diet. This suggests that both these factors might be responsible for body deformities. The present results proved that only the non-commercial starter is suitable for juvenile E. perenurus rearing under controlled condition, and that none of the commercial starters can be recommended.     

The effect of photoperiod, tank colour and light intensity on growth of larval haddock

In two separate experiments, haddock (Melanogrammus aeglefinus) larvae were raised under different photoperiods (24L : 0D or 15L : 9D), or different combinations of tank colour (black or white) and light intensity (1.1 mol s^–1 m^–2 or 18 mol s^–1 m^–2). Growth (0.8% day^–1 in standard length; 2.9% day^–1 in body area) and survival (2%) were not significantly different between photoperiod treatments after 35 days. Larval survival was greater in white versus black tanks after 41 days (2% versus l%, respectively). Growth of larvae was impaired in black tanks at low (1.1 mol s^–1 m^–2) light intensity (0.8% day^–1 in standard length and 2.2% day^–1 in body area versus 1.1% day 21 in standard length and 3.1% day^–1 in body area, for all other treatments). Transmission and reflection of light was low in black tanks at low incident light, and there was very little upwelling light. The resultant poor prey to background contrast probably resulted in larvae being unable to consume sufficient food to sustain a level of growth comparable to that in other treatments.     

Artificial spawning of carp (Cyprinus carpio L.): differences between females of Polish strain 6 and Hungarian strain W treated with carp pituitary homogenate, Ovopel or Dagin

Investigations of the effects of controlled reproduction were conducted on carp females of Polish strain 6 and Hungarian strain W after ovulation stimulation with carp pituitary homogenate (CPH) (0.3 mg+2.7 mg kg^?1 body weight), Ovopel (1/5+1 pellet kg^?1 body weight) or Dagin (1 dose kg^?1 body weight). In both strains, the highest percentage of spawning females was found after the Ovopel treatment. After treatments with CPH and Dagin this percentage did not differ in strain 6; however, after Dagin, it was higher in fish of strain W. After CPH or Ovopel stimulation the females of line 6 yielded eggs of higher weight compared with line W. After the Dagin treatment the weight of eggs obtained from females, both strains was similar but much lower than after the two remaining agents. The quality of eggs expressed both by the percentage of fertilization and that of living embryos after 24 and 36 h incubation was similar in the two strains only in the group treated with Ovopel. After CPH application eggs of better quality were obtained from strain 6 compared with strain W; however, after the treatment with Ovopel, eggs of much better quality were noted in strain W. In general, the best effects of reproduction were recorded in the case of Ovopel and the poorest in that of Dagin. Females of strain 6 yielded eggs of a higher weight but the percentages of spawning females were higher in strain W after each of the applied spawning agents. A new approach to this problem consisted in investigating the interaction between ovulation stimulators and origin of females of fish treated with Dagin.     

Quantifying the dietary biotin requirement of the catfish,Clarias batrachus

Asian catfish, Clarias batrachus, were fed semi-purified basaldiets containing 0, 0.1, 0.5, 1, 3 and 5 mg biotin kg^–1diet for 60 days. Fish fed the control diet (no biotin) showed(P < 0.05) higher mortality, lower weight gain, specificgrowth rate (SGR), feed efficiency ratio (FER) and protein efficiencyratio (PER) than in fish fed diets supplemented with biotin. The highestweight gain, SGR, FER and PER were noticed in fish fed 1 mg biotinkg^–1, followed by 0.5, 5, 3 and 0.1 mg biotinkg^–1, except for PER (followed by 0.5, 5, 0.1 and 3 mgbiotin kg^–1). Quadratic analysis showed that the optimumdietary biotin requirements for maximal weight gain, PER and PER were2.49, 2.54 and 2.52 mg kg^–1, respectively. Liver biotinconcentrations were influenced by levels of biotin in the diet.Concentration of liver biotin increased as level of dietarysupplementation increased and no biotin was detected in the liver of thecontrol fish. Liver pyruvate carboxylase and acetyl CoA carboxylaseactivities were higher in fish fed biotin-supplemented diets than incontrols. Biotin concentrations, pyruvate carboxylase and acetyl CoAcarboxylase activities in liver associated with normal growth rangedfrom 10.59 to 10.66 g g^–1, 147.97 to 148.18 units mgprotein^–1 and 12.76 to 12.78 units mg protein^–1, respectively. Biotin deficiency symptoms such as anorexia, darkskin colour and convulsions were observed in fish fed the control diet.The optimum dietary biotin requirement for maximal growth of C.batrachus is about 2.49 mg kg^–1 diet.     

Effects of dietary carnitine and lipid on growth and body composition of hybrid striped bass (Morone chrysops ♀× M. saxatilis ♂)

A study was undertaken to investigate the effects of graded dietary levels and different types of carnitine on hybrid striped bass (Morone chrysops × M. saxatilis %) fed different levels of lipid. An incomplete factorial design was utilized in which diets containing lipid at either 5 or 10% were supplemented with l-carnitine at 0, 500, or 1000 mg kg^–1 diet, dl-carnitine at 1000 mg kg^–1 diet, or carnitine chloride to provide 1000 mg carnitine kg^–1 diet. Juvenile hybrid striped bass (3.3 g fish^–1) were stocked into individual 38-l aquaria connected as a brackish water (6), recirculating system and fed each diet in triplicate for 9 weeks.Supplementation of the diet with 1000 mg carnitine kg^–1 increased muscle carnitine from 35.5 to 47.7 g g^–1 tissue. Carnitine supplementation did not result in increased weight gain regardless of carnitine level or type; however, weight gain showed a significant (p<0.05) response to dietary lipid with fish fed diets containing 10% lipid growing 34% more than fish fed diets with 5% lipid. The hepatosomatic index also was unaffected by diet, but the intraperitoneal fat (IPF) ratio was significantly elevated (5.1 vs 3.2%) in fish fed diets with 10% lipid compared to those fed diets with 5% lipid. Fish fed diets containing 1000 mg carnitine kg^–1 had increased IPF ratio values at 4.7% compared to 3.9% for fish fed the basal diet. Liver lipid also was responsive to dietary treatment, increasing from 6.7 to 8.8% of wet weight as dietary lipid increased from 5 to 10%. The relative quantities of triglycerides, free fatty acids and phospholipids in muscle and liver were not influenced by carnitine level, carnitine type or dietary lipid level. Supplementation of carnitine does not appear to be beneficial to hybrid striped bass based on either growth performance or body composition.     

The effect of dietary vitamin E on the pleopodal egg number of Astacus leptodactylus (Eschscholtz, 1823)

The effect of vitamin E on the pleopodal egg number of Astacus leptodactylus (Eschscholtz, 1823) was studied. Crayfish were fed 2% of their total wet weight daily with vitamin E supplemented diets and a control for 70 days. The vitamin E content of the control diet, diet 1, diet 2 and diet 3 were 20 mg kg^–1, 40 mg kg^–1, 80 mg kg^–1 and 160 mg kg^–1 respectively on a dry weight basis. Vitamin E levels of the control and experimental diets were analysed by High Performance Liquid Chromatography. Results showed that diets containing supplemental vitamin E were associated with an increase in the number of pleopodal eggs. The best result was obtained with diet 2 containing 80 mg kg^–1 supplemental vitamin E.     

Oxygen consumption and responses to hypoxia of ammocoetes of the southern hemisphere lampreyGeotria australis

The standard rate of oxygen consumption of ammocoetes (larvae) ofGeotria australis with a mean weight of c. 0.5 g was 9.6, 31.4 and 59.4l g^–1 h^–1 at 4.5, 15.5 and 25.0°C respectively, which gives an overall Q₁₀ of 2.4. The regression coefficient for the logarithmic relationship between oxygen consumption and body weight at 15.5°C was 0.704. The ammocoetes ofG. australis have a much lower rate of oxygen consumption at 15.5 and 25.0°C than those of holarctic lampreys. This presumably reflects the lower oxygen delivery pressure to their tissues and helps account for their slow growth rate. At 15.5°C, ammocoetes ofG. australis emerged from the substrate at 21–25 mm Hg and, unlike those of the Northern HemisphereIchthyomyzon greeleyi, died at 14–17 mm Hg. Thus, despite having a thinner water/blood barrier in the gills and blood with a higher oxygen affinity and capacity than holarctic ammocoetes, the larvae ofG. australis cannot survive very low dissolved oxygen tensions. This is apparently related to an inability of larvalG. australis to meet the high oxygen requirements of the respiratory pump at these oxygen tensions. During metamorphosis, oxygen consumption at 15.5°C rose from approximately 27l g^–1 h^–1 at the beginning of transformation to 33.2l g^–1 h^–1 by Stage 3 and then rapidly to 66l g^–1 h^–1 at Stage 6. It remained near this level in Stage 7 and the downstream migrant.     

Acute Toxicity of Synthetic Pyrethroid Cypermethrin on the Common Carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) Embryos and Larvae

In this study, the toxic effects on the embryos and larvae of the common carp were used as a model to investigate the synthetic pyrethroid pesticide, cypermethrin, which contaminates aquatic ecosystems. Data obtained from the cypermethrin acute toxicity tests were evaluated using the Probit Analysis Statistical Method. The control and eight test experiments were repeated five times. The number of dead embryos significantly increased in response to cypermethrin concentrations 0.0001, 0.001, 0.01, 0.1, 1, 2, 4 and 8 μg l⁻¹ (p<0.05 for each case). The 48 h LC₅₀ value (with 95% confidence limits) of cypermethrin for common carp embryos was estimated at 0.909 (0.256–5.074) μg l⁻¹. Dose–response decreases in hatching success were recorded as 87.4, 85.0, 80.2, 71.4, 56.3, 48.6, 38.8 and 23.5%, respectively. The lowest concentration of cypermethrin (0.0001 μg l⁻¹) produced a significant increase in the number of dead larvae compared to the control group (p<0.05). The number of dead larvae significantly increased with increasing cypermethrin concentrations exposed for 1–96 h (p<0.05). The highest concentration (8 μg l⁻¹) showed the highest larvae mortality. The 96 h LC₅₀ value (with 95% confidence limits) of cypermethrin for common carp larvae was estimated at 0.809 (0.530–1.308) μg l⁻¹. The results of the study suggest that low levels of cypermethrin in the aquatic environment may have a significant effect on the reproduction and development of carp.     

The effect of seawater flow and temperature on metamorphosis and postlarval development in great scallop

Variations in growth and survival of hatchery-reared post-metamorphicjuveniles of great scallop Pecten maximus prompted anexamination of settlement and postlarval development. The effects ofseawater flow and temperature on great scallop metamorphosis andpostlarvae were studied over a 4–5 week period. In allexperiments, and regardless of environmental conditions, great scallopmetamorphosed after a 2–3 week period with values of 35 to70%. Subsequently, spat numbers increased slightly. Spatmortality generally occurred from the third week onward and reachedlevels as high as 30% by the fifth week under standardconditions. At 20 °C, however, 60% mortality levels wererecorded. Differences in spat growth rate, ranging from 37 to 45 mday^–1, were noticed at different seawater flow ratesbut no clear tendency could be discerned. Temperature affected spatgrowth with an increase in size from 24 m day^–1 at15 °C to 35 m day^–1 at 18 °C. Conversely,growth was suppressed at 20 °C (14 m day^–1).For optimal metamorphosis and postlarval development in great scallop, aseawater flow of 4.3 L h^–1 per sieve and a temperatureof 15 °C are recommended.     

Utilization of carotenoids from various sources by rainbow trout: muscle colour,carotenoid digestibility and retention

Rainbow trout (Oncorhynchus mykiss) with a mean (sd) weight of 120 (2) g were fed diets supplemented with astaxanthin extracted from the yeast Phaffia rhodozyma (OY1 = 50 mg carotenoids kg^–1 feed, OY2 = 100 mg carotenoids kg^–1 feed), astaxanthin (AX = 100 mg astaxanthin kg^–1 feed) and canthaxanthin (CX = 100 mg canthaxanthin kg^–1 feed) for 4 weeks. Muscle analyses at the end of the experiment indicated a significantly higher carotenoid concentration in the AX group, while CX and OY1 groups were similar in spite of the differences in dietary concentration. The measure of total muscle colour difference (E^* _ab) between initial samples and 4 week ones was higher for the AX fish group but showed no significant difference between OY1, OY2, and CX. The hue and the reflectance ratio (R₆₅₀:R₅₁₀) of fish muscle increased in proportion to carotenoid intake. Digestibility (ADC) of yeast astaxanthin in OY1 and OY2 groups was significantly higher than that in the AX group. Canthaxanthin ADC was about one sixth of that of astaxanthin (AX group). Carotenoid retention in the muscle, expressed as a percentage of carotenoid intake, was higher for the AX group than that recorded for OY1 and OY2. According to ADC, carotenoid retention showed a marked lower value for the CX group. Muscle retentions were similar for astaxanthins from both sources.     

The efficacy of a single intraperitoneal injection of either flumequine or oxytetracycline hydrochloride in prevention of outbreaks of atypical Aeromonas salmonicida infection in goldsinny wrasse, Ctenolabrus rupestris L., following stress.

In this investigation, the efficacy of a single intraperitonealinjection of either flumequine or oxytetracycline hydrochloride to preventoutbreak of atypical Aeromonas salmonicida infection ingoldsinny wrasse, Ctenolabrus rupestris, following stresswas studied. Six groups of goldsinny wrasse, each of 50 individuals, weretreated with an intraperitoneal injection of either propylene glycol : saline(50 : 50), 200 mg kg^–1 of oxytetracycline or 50mg kg^–1 of flumequine dissolved in propyleneglycol : saline (50 : 50). Three days following medication the fish in allgroups were stressed by an intraperitoneal injection of prednisolone acetate(0.05 ml) and a rise in seawater temperature from 9 to 11°C. Mortality was observed daily for 21 days. Flumequine wasthe more effective with a mean cumulative mortality of 5% compared tooxytetracycline with 54%. The mean cumulative mortality in the unmedicatedcontrol groups was 84%. Bacterial examination of kidneys from dead fishconfirmed the presence of atypical A. salmonicida as theprobable cause of death. Minimum inhibitory concentration (MIC) values forflumequine and oxytetracycline against the isolated A.salmonicida were determined to 0.13 gml^–1, and 2.0 g ml^–1,respectively.     

Replacement of Artemia with Moina micrura in the rearing of freshwater shrimp larvae

The effect of an abrupt change in the live diet of shrimp larvae was investigated by replacing Artemia with Moina micrura. The control treatment consisted of feeding Artemia throughout the rearing period (regime A), while in the other treatments the onset of Moina feeding was arbitrarily chosen at larval stages iv (A3M), vi (A5M), viii (A7M) and x (A9M). No significant differences ( = 0.05) were observed among the treatments during larval production, mean stage development (MSD) and growth of postlarvae. The mean (SD) yields of postlarvae (PL) were 11.97 (1.98), 15.10 (2.92), 14.72(1.56), 13.51 (1.74) and 12.70 (1.40) PL l^–1 respectively for the feeding regimes A3M, A5M, A7M, A9M and A. Up to stage v, the ingestion rate in the Moina treatment was as low as 0.01–0.47 larva^–1 h^–1 compared with that in the Artemia treatment (0.29–1.77 larva^–1 h^–1). However, the ingestion of Moina increased from stage vi–vii onwards.     

Quantitation of inert feed ingestion in larval silver sea bream (Sparus sarba) using auto-fluorescence of alginate-based microparticulate diets

The ingestion of an inert feed as a sole food source was investigated in larval silver sea bream (Sparus sarba) fed an alginate-based microparticulate diet. Using the auto-fluorescent properties of pigments associated with the alginate base, ingestion and gut content were investigated over a 6 h experimental period in fed and unfed larvae. By extracting and measuring chlorophyll a (Chl a) and phaeopigment content of feeding larval fish and relating this to standardized Chl a and phaeopigment content of the diet, relative to diet weight, it was determined that individual fed 7-day old larvae had a maximum gut content of 1.05±0.09 g diet while 14-day old fed fish had a maximum gut content of 3.17±0.90 g diet. On average, the gut content of 14-day old fish was 2.89 times greater than the gut content of 7-day old fish. The dry weight of larval sea bream increased from 43±4.2 g at day 7 to 134.3±20.4 g at day 14 indicating that growth of fish fed this inert feed was substantial. Gut pigment dynamics suggested that Chl a was degraded to phaeopigments by 7-day but not 14-day old larvae and the individual gut dietary content varied considerably in 14-day old fish. The maximum Chl a and phaeopigment content in larval sea bream was 0.4 ng ind^–1 and 0.55 ng ind^–1 for 7-day old fish and 1.54 ng ind^–1 and 2.81 ng ind^–1 for 14-day old fish respectively. The present method may potentially allow simple and direct assessment of larval fish feed ingestion in both an experimental and commercial setting.     

Use of egg custard augmented with cod liver oil and Moina micrura on production of freshwater prawn postlarvae

Use of egg custard augmented with cod liver oil (CLO) fed during the day, and of an overnight feed with Moina micrura, were evaluated in terms of its effects on production of freshwater prawn (Macrobrachium rosenbergii) postlarvae (PL). Four levels of CLO (0, 1,3 and 5%) were tested. Significantly higher mean (sd) productions, ranging from 11.27 (1.16) to 13.02 (1.70) PL l^–1, were obtained for larvae fed egg custard enriched with CLO compared with that of 7.83 (1.58) PLl^–1 for larvae fed egg custard without CLO. The development and survival of larval stages were also higher for the CLO diets. The -3 highly unsaturated fatty acid (HUFA) in egg custard increased with increasing CLO level (0–5%). The fatty acid composition of postlarvae reflected the composition of the diet.     

Utilization of lipids by Dentex dentex L. (Osteichthyes, Sparidae) larvae during lecitotrophia and subsequent starvation

Total lipids, lipid classes and their associated fatty acids were measured in developing eggs, yolksac larvae and starving larvae (from fertilized egg to day 9 after hatch) of the common dentex Dentex dentex (L., 1758). The larvae of common dentex during lecitotrophia and subsequent starvation consumed 1.6 g of total lipid per larvae per day. The overall decrease was mainly due to utilization of the major neutral lipids, TAG and SE (0.5 and 0.6 g larvae^–1 day^–1, respectively) which was 3.4-fold greater than that of the the major phosphoglycerides (primarily PC by 0.2 g larvae^–1 day^–1). There was net synthesis/conservation of PE during the first half of the study period before it decreased rapidly (0.2 g larvae^–1 day^–1) during the second half. PUFAs were principally catabolized (468.6 ng larvae^–1 day^–1), primarily 22:6(n-3), 20:5(n-3) and 20:4(n-6) (221.8, 58.5 and 12.1 ng larvae^–1 day^–1, respectively). Saturated and monounsaturated fatty acids were also utilized (227.2 and 256.7 ng larvae^–1 day^–1, respectively), principally 16:0 and 18:1(n-9) that were both consumed at 149.8 and 156.7 ng larvae^–1 day^–1, respectively. The rank order of utilization of fatty acids (ng larvae^–1 day^–1) by D. dentex larvae from total lipids, PC and TAG coincided with the order of abundance of the different fatty acids in the respective lipid fractions. However, in PE, the most abundant fatty acid, DHA, was relatively conserved and 16:0, the second most abundant fatty acid, was catabolized to the greatest extent. D. dentex showed a pattern of lipid metabolism during early development similar to that of marine larval fish from temperate waters whose eggs contain high levels of total lipids, including an oil globule, and which preferentially utilize neutral lipids as the primary energy source.