Lipid composition of yellowtail flounder (<Emphasis Type="Italic">Limanda ferruginea</Emphasis>) in relation to dietary lipid intake

Condition indices (CI), hepatosomatic indices (HSI) and proximate, lipid and fatty acid composition of wild and laboratory-reared yellowtail flounder (Limanda ferruginea) (Storer, 1839) were compared from data taken throughout spring and summer 1996–1998. Cluster analysis was performed on the fatty acid signatures of these two groups along with a commercial diet and several invertebrate species to determine possible feeding patterns in Conception Bay, Newfoundland. HSI and levels of storage fat were significantly higher in the muscle and liver of laboratory-reared yellowtail flounder, indicating an efficient absorption of dietary lipid and an increase in fat deposition. Fatty acid analysis of the liver showed that wild fish contained significantly higher proportions of the essential fatty acids 20:46, 20:53 and 22:63; whereas proportions of 18:1 and 18:26 were significantly higher in all fractions of lipid examined from laboratory-reared fish than they were from wild fish. Polar fractions of lipid were more similar than the neutral fraction of lipid when comparing wild and laboratory-reared fish. Taken together, the differences in CI, HSI, proximate and fatty acid composition suggest that feeding commercial diets to L. ferruginea can cause changes in patterns of lipid deposition and metabolism. Cluster analysis of marine plankton, sedimenting particulate matter, wild invertebrates, the commercial diet and fish tissues showed that the fatty acid signatures of both wild and laboratory-reared yellowtail flounder closely resembled their respective food items. Fatty acid signatures from wild fish were more closely related to plankton and settling particulate matter, suggesting relatively few steps in the food web leading to yellowtail flounder. In addition to the resemblance between fatty acids in the commercial diet and the tissues of laboratory-reared yellowtail flounder, these fish had similar fatty acid signatures to those of wild invertebrates.Communicated by J.P. Grassle, New Brunswick     

Comparative studies of liver and brain glycogen content of male and female Clarias batrachus (L.) after exposure of different doses of arsenic

Different doses of arsenic (As) were used to investigate comparative toxicity on the liver and brain glycogen content on male and female Indian catfish Clarias batrachus (L.). As-induced effects were associated with gender, dose (5, 10, or 15?mg?L^?1), and varying time periods (48, 96, or 144?h). It was noted that As produced dose- and time-dependent liver glycogenolysis and late brain glycogenolysis. Liver glycogenolysis was significantly increased after 48?h at all three As doses. At the highest dose 15?mg?L^?1, liver glycogen were markedly diminished at in both male and female fish, but in females more reduction was observed than in males. However, with brain glycogen, the significant decrease was noted at 144?h with all three dose levels in both genders, with male being more susceptible. Thus, this study indicates that As produces glycogenolysis. The reduction in the liver glycogen content was more pronounced in female than in the male fish, whereas brain glycogen content decrease was more prominent in males.     

Fatty-acid composition of ovulated eggs from wild and cultured turbot (Scophthalmus maximus) in relation to yolk and oil globule lipids

The fatty-acid composition of lipids from ovulated eggs of wild and cultured turbot was investigated in order to estimate the nutritional requirements during embryonic and early larval development. Lipid comprised 13.8±0.5% (n=5) and 13.2±0.7% (n=7) of the egg dry weight in wild and cultured turbot, respectively. Polyunsaturated fatty acids (PUFA) of the (n-3) series accounted for 39% of total fatty acids in total lipid of both wild and cultured fish. The predominant (n-3) FUFA was docosahexaenoic acid (22:6 n-3), which also was the most abundant fatty acid in turbot eggs and comprised 24 and 23% of the total egg fatty acids in wild and cultured fish, respectively. Phospholipids, triacylglycerols and cholesterol-wax esters of turbot eggs all exhibited a specific fatty-acid profile distinctly different from that of total lipid. The general pattern of the fatty-acid distribution in lipids of eggs from wild and cultured turbot was similar, but the relative amount of 18:2(n-6) was considerably higher and 20:1(n-9) slightly higher in cultured fish. These differences were extended to all lipid classes and probably reflect the dietary intake of certain vegetable and marine fish oils. Calculations based on light microscopical studies showed that 55 to 60% of the total lipids in cultured turbot eggs are confined to the oil globule. The size of the oil globule remained constant during embryogenesis, and a reduction in size occurred first after hatching and mainly after yolk depletion. This implies that the total amount of lipids utilised during the embryonic development is considerably less than the total lipids present in ovulated turbot eggs. Comparison of the fatty-acid composition of total lipids from eggs and vitellogenin of wild turbot reveals that egg lipids contained a lower level of saturated and a higher level of monounsaturated fatty acids. Eggs also contained wax esters, which were not detected in vitellogenin, suggesting that vitellogenin is not the only source of lipids for turbot eggs.     

Maternal allocation of lipid classes and fatty acids with seasonal egg production in Atlantic cod (Gadus morhua) of wild origin

A suite of characteristics is often used to assess egg quality as these properties potentially play important roles in progeny survival and growth. Our objective was to assess egg characteristics including lipid biocomposition of an iteroparous, batch-spawning teleost of wild origin. Maternal allocation to egg number was generally dome-shaped (5 of 8 females) and egg size declined over the breeding season for eight breeding pairs of wild Atlantic cod (Gadus morhua) (n = 43 batches). Egg lipid composition ranged considerably among females and between egg batches within females (e.g., phospholipids 40–86 %; polar 47–87 % and neutral lipids 15–52 % of total lipids; polyunsaturated fatty acids 16–50 % of total fatty acids). Principal component analyses revealed significant inter-relationships among maternal traits, batch sequence and fecundity, and egg size and composition. Seasonal trends with regard to lipid deposition were variable; three females showed consistent declines in lipid parameters (μg egg⁻¹) with both batch number and egg diameter, one female showed consistent increase and the four remaining females showed no trend. The three females that exhibited seasonal declines in egg lipid content were characterized as having high fertilization success (>75 %). Our findings highlight the variability in lipid allocation to eggs of batch spawners of wild origin and characterize the composition of endogenous reserves available during embryogenesis and yolk sac larval stages.     

Lipid composition of<Emphasis Type="Italic"> Symphodus ocellatus</Emphasis> (Perciforme: Labridae) in the north-western Mediterranean: influence of two different biotopes

The lipid content and fatty acid composition of the small common wrasse Symphodus ocellatus was analysed within two populations located in very different biotopes on the French shore: a Caulerpa taxifolia meadow located in Cap Martin and a Posidonia oceanica bed located in Villefranche. Polar lipids represented 82–90% of the total lipid in adult female livers, gonads and in eggs. Cholesterol in gonads and eggs and triacylglycerols in livers were the dominant neutral lipids. Differences in lipid classes were found in livers between the two populations, but not in their gonads and eggs. Moreover, a quantitative difference in total lipid content was evident. Young fish living on the C. taxifolia meadow in winter had 21% less lipid than those living on the P. oceanica bed. The populations of S. ocellatus showed differences between triacylglycerol versus phospholipid fatty acid compositions and between gonad versus liver fatty acid compositions. Moreover, a significant difference was found between both populations in their liver triacylglycerol fatty acid compositions, suggesting a difference in diet. Gut content analysis supported this hypothesis as it showed important differences in the ingested preys between the two populations in January (planktonic vs. benthic, frequency of isopods) and in June (frequency of gastropods). Thus, we found that the fish populations from Villefranche and Cap Martin showed significant differences in body lipids due to different nutritional habits.Communicated by S.A. Poulet, Roscoff     

Changes in the content and fatty acid composition of lipid in an isolated population of the capelin Mallotus villosus during sexual maturation and spawning

Changes in the wet weights and lipid contents of muscle, liver and gonad were determined in male and female Mallotus villosus in Balsfjorden, northern Norway, in 1981, from January, when gonadal development becomes noticeable, until May when the fish are spawning. Fatty acid compositions of tissue lipids were also determined. Over 4 mo prior to spawning, the weight of muscle in female capelin decreased by 32% while the weight of the ovary increased exponentially by 830%. In males the weight of the muscle remained constant and that of the testis decreased slightly. The lipid contents of the muscle of both males and females decreased by 76% over the period and an inverse relationship existed between the water and lipid contents of muscle in both sexes. Male liver weight remained constant over the period of study whereas female liver weight increased transiently by 300% between January and March. 38% of the lipid lost from female muscle was accounted for by lipid deposited in ovary whereas negligible amounts of the lipid lost from male muscle was accounted for by lipid in the testis. Gonadal lipid was always richer in polyunsaturated fatty acids than muscle lipid and, immediately prior to spawning, 42% of the fatty acids in ovarian lipid were polyunsaturated. Muscle lipid of males and females showed a progressive increase in the percentage of the long-chain monoenes 20:1 and 22:1 between January and May. It is concluded that male capelin catabolise more of their muscle lipid reserves than females in the 4 mo prior to spawning and that most of the lipid catabolism in males is associated with physical activity. Conversely, females deposit much more of their muscle lipid in gonads than males, although considerable selectivity occurs in the mobilisation of fatty acids from muscle lipid into ovarian lipid. Additionally, biosynthesis of gonadal constituents accounts for a considerable proportion of the lipid catabolised in females.     

Lipid classes and their content of n-3 highly unsaturated fatty acids (HUFA) in Artemia franciscana after hatching, HUFA-enrichment and subsequent starvation

The distribution of n-3 highly unsaturated fatty acids (HUFA) over the major neutral and polar lipid classes was determined for two predominant types of live food used in the larviculture of marine fish and shrimp, i.e. freshly hatched and HUFA-enriched Artemia, and compared with data reported in the literature for wild copepods, representing the natural diet of these larvae. Lipid class composition and their content of n-3 HUFA, particularly eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), were assessed in freshly hatched, HUFA-enriched and subsequently starved Artemia franciscana. The n-3 HUFA enrichment was based on feeding Artemia a lipid emulsion in which either fatty acid ethyl esters (EE, diluted with olive oil) or triacylglycerol (TAG) provided a level of 30% n-3 HUFA. Enrichment of Artemia with either type of the lipid emulsions resulted in an increase of total lipid content from 20.0 to 28.2–28.7% of dry matter mainly due to the accumulation of neutral lipid, primarily TAG (from 82 to 158 mg g⁻¹ dry wt in freshly hatched and 24-h enriched Artemia). Enriched brine shrimp utilized up to 27–30% of their TAG content during 72 h of starvation at 12 °C. The absolute tissue concentrations of polar lipids remained constant at 71 to 79 mg g⁻¹ dry wt throughout the enrichment and subsequent starvation. The level of n-3 HUFA increased drastically during enrichment from 6.3% of total fatty acids (8.2 mg g⁻¹ dry wt) in freshly hatched nauplii to between 20.4 and 21.8% (40.4 to 43.2 mg g⁻¹ dry wt) in 24-h enriched Artemia and was not significantly affected by the source of n-3 HUFA. During starvation, 18:0, 20:4n-6 and 20:5n-3 were retained, whereas 18:4n-3, 22:5n-3 and 22:6n-3 were specifically catabolized. The major polar lipids, phosphatidylethanolamine (PE) and phosphatidylcholine (PC), of freshly hatched Artemia showed very low levels of DHA (<0.1% of total fatty acids) and carried about 45% of the total EPA present. Enrichment with either of the emulsions resulted in an increase of the neutral lipid fraction which concentrated >64% of the EPA and >91% of the total DHA present. This is in sharp contrast with the high levels of n-3 HUFA, in particular DHA, in the polar lipid fraction reported for wild copepods. The contrasting distribution of DHA in the neutral and polar lipid fractions of enriched brine shrimp compared to the natural diet may influence the efficacy of this essential fatty acid for marine fish larvae in aquaculture systems. Received: 10 June 1997 / Accepted: 8 August 1997     

Lipid storage and composition in tropical surgeonfishes (Teleostei: Acanthuridae)

The lipid composition of tropical marine reef fishes is poorly known, despite their use as food by local human populations and recent interest in health-related benefits of fish lipids. We examined the composition of lipids from epaxial muscle, liver, and two storage sites [mesenteries surrounding the gut (intraperitoneal fat, IPFs) and retroperitoneal fat bodies (FBs) posterior to the peritoneal cavity] in three species of surgeonfishes from Ishigaki Island, Japan: Naso lituratus (Bloch and Schneider, 1801), Acanthurus lineatus (Linnaeus, 1758), and A. bariene (Lesson, 1830). Triacylglycerols dominated all samples of neutral lipid and constituted ≥ 99% of FBs and IPFs. Polar lipids generally contained large fractions of phosphatidylethanolamine and phosphatidylcholine. Quantified fatty acids ranged in length from C₁₄ to C₂₄. C₁₆ fatty acids prevailed (>35% of neutral fatty acids, >23% of polar fatty acids), although C₁₈ (>16 and >14%, respectively) and C₂₀ acids (>8 and >19%, respectively) were also common. Saturated fatty acids, dominated by palmitic acid (16:0), comprised 38.7 to 50.7% of acids from neutral lipids and 30.8 to 41.1% from polar lipids. The most common monounsaturated acids were 18:1n9 and 20:1n9. Polyunsaturated acids were prevalent in polar lipids (especially 20:4n6, 20:5n3, 22:2n3, 22:5n3, 22:5n6 and 22:6n3). Common polyunsaturated acids of neutral lipids were 18:2n6, 18:4n3, several n-3 and n-6 C₂₀ acids, 22:2n3 and 22:5n3. IPF and FB were almost identical across species, and lipids of fat bodies (IPFs, FBs) were more similar to those of muscle than those of liver for all three species. The FBs appear to constitute an accessory storage site, which overcomes constraints on lipid storage imposed by a small, inflexible abdominal cavity that contains both viscera and consistently voluminous gut contents. Fatty acid signatures indicate that largely overlooked epiphytic or epilithic diatoms contribute significantly to lipid acquisition. The combination of large quantities of both saturated and n-3 and other polyunsaturated fatty acids in surgeonfishes, in contrast to low saturates and high polyunsaturated acids in lipids of commercially important cool-water fishes, suggests that a study of dietary effects of fish lipids on human inhabitants of the tropics may be instructive insofar as human health and nutrition are concerned. Received: 16 March 1998 / Accepted: 6 August 1998     

Lipid and protein utilisation during early development of yellowtail kingfish (<Emphasis Type="Italic">Seriola lalandi</Emphasis>)

The pelagic yellowtail kingfish Seriola lalandi has become a target species for aquaculture in Asia and Australasia. Australasian production is reliant on larviculture from eggs of captive brood stock; however, knowledge regarding the nutritional requirements of larvae of this species is still scarce, particularly in relation to lipids. As a first step in establishing these requirements, eggs and larvae from captive S. lalandi brood stock were examined for differences in total protein, total lipid and lipid classes between individual spawning events, over the spawning season, and during larval development from fertilisation to 15 days post hatch. Results indicate that total protein egg⁻¹ varied significantly between individual spawning events within a season, but neither total lipid nor total protein egg⁻¹ varied significantly across the spawning season. Brood stock egg lipids were made up of approximately 60% phospholipid, 25% wax and/or sterol esters (WE), 15% triacylglycerol (TAG), and small amounts of sterols and free fatty acids. During the early larval period, both WE and TAG were utilised concurrently for energy. The larvae experienced very high mortality around 5–7 days post hatch, which coincided with very low levels of all neutral lipid classes. Although many other factors may also influence larval mortality, these results indicate that lipid provisioning may be an important factor in larval survival during the critical period around first-feeding in this species. Examination of ratios of TAG:ST, often used as a condition index in fish larvae, suggested that some of the larvae were suffering from starvation. However, as egg-derived WE appears to provide a significant source of energy during the early larval period in S. lalandi, it is suggested that WE should be included in any index of larval nutritional state.     

Increased docosahexaenoic acid levels in total and polar lipid of European sea bass (Dicentrarchus labrax) postlarvae fed vegetable or animal phospholipids

A 6-week feeding trial was conducted with 44-d-old European sea bass (Dicentrarchus labrax L.) in order to examine the effect of various dietary phospholipid (PL) sources on the incorporation of n-3 highly unsaturated fatty acids (HUFA) in tissue lipids. From weaning onwards the fish received diets prepared by coating different lipid fractions (7.5% diet) on an extruded basal diet (92.5% diet). The two PL-free control diets contained 0.5 and 2% of an emulsifier blend, respectively. Seven other diets contained 2% PL, differing by their purity and origin (vegetable or animal). All diets were rendered isolipidic by the addition of hydrogenated coconut oil. Feeding the PL-supplemented diets, except the diet containing hydrolyzed soybean PL (lyso PL), resulted in a higher survival and a 10 to 30% better growth as compared to the PL-free diets. No difference according to the PL origin was observed. The sea bass final lipid content increased with increasing body weight. Also the lipid class composition of the fish was clearly correlated with the final weight gain. Total neutral lipid increased from 51% of total lipid (initial fish) to 76% for fish fed the PL-free diets, and up to 88% for fish fed the sunflower PL. Weaning the fish on the experimental diets induced important changes in their fatty acid profiles characterized by a decrease in 18:3n-3, 20:5n-3 and 20:4n-6 and an increase in saturated fatty acids and 22:6n-3 (DHA). According to the fatty acid composition of both total and polar lipid, the weaned fish could be divided into three groups reflecting the dietary fatty acids: a group fed the vegetable PL, a group fed the animal PL and a PL-deprived group. An effect of dietary PL on the incorporation of dietary n-3 HUFA, more particularly DHA, was noticed. For a similar supply of DHA through the neutral lipids in the diet, fish fed PL-supplemented diets (except for the lyso PL diet) had 10 to 25% higher DHA levels in total and polar lipid than PL-deprived fish. This PL effect was already clear at the end of the weaning and was not related to the presence of n-3 HUFA in the PL source, as suspected in a previous study when feeding egg yolk PL. A better incorporation of DHA was not obtained by replacing the PL by an emulsifier or by lyso PL with higher emulsifying properties. Present results confirm a role of dietary PL in the absorption of dietary neutral lipids, by a mechanism other than emulsification. Received: 27 May 1997 / Accepted: 30 June 1997     

Does juvenile experience affect migration and spawning of adult Atlantic salmon?

Summary This paper documents differences in seasonal time of river ascent and descent, and instream behavior of adult wild and sea-ranched Atlantic salmon (Salmo salar) of the Norwegian River Imsa stock during the period 1981–1989. Wild fish use River Imsa as a nursery, and at an age of 2 years most of them migrate to the sea as smolts. The sea ranched fish are hatchery reared offspring of the River Imsa stock and are released as smolts at the mouth of the river. They are thus deprived of juvenile river life and a downstream smolt migration. Wild and sea ranched salmon feed for 1 or more years in the Norwegian Sea before homing as spawners. Both groups returned simultaneously to coastal Norway, but sea ranched fish ascended the river later and descended sooner after spawning than wild fish. All wild females and almost all wild males (96.2%) spawned in the river, whereas 13.5% and 36.7%, respectively, of the mature sea-ranched females and males left the river unspawned. The annual number, but not the proportion, of unspawned fish increased with increasing density of adult salmon in the river. Unspawned females were medium sized and small (45–70 cm); unspawned males were medium sized and large (50–90 cm). Independent of the density of spawners in the river, sea ranched fish moved up- and downstream the river more often than wild fish. More than 20% of the sea-ranched salmon and less than 1% of the wild salmon passed a trap 100 m above the river outlet more than once in each direction during the same spawning reason. Moreover, sea-ranched salmon were about twice as often seriously injured during spawning as wild fish. Lack of juvenile experience from the river may be the main reason for the behavioral differences between sea-ranched and wild fish. Offprint requests to: B. Jonsson     

Impact of starvation and of feeding algal and artificial diets on the lipid content and composition of juvenile oysters (Crassostrea gigas) and clams (Tapes philippinarum)

The present study evaluated the effect of starvation and of feeding various algal and lipid-supplemented diets on the lipid content and lipid class distribution in the polar and neutral lipids of early juvenile oysters (Crassostrea gigas) and clams (Tapes philippinarum L.). T. philippinarum was starved, fed a mixed algal diet [Tetraselmis suecica and Isochrysis galbana (clone T-Iso)] or solely T. suecica at three different feeding rations, either supplemented or not supplemented with lipid emulsions. C. gigas was fed T. suecica with and without the supplementation of lipid emulsions or liposomes. When T. philippinarum and C. gigas were fed solely T. suecica, no qualitative and only minor quantitative differences were observed between the lipid class profile of both species. The major neutral lipids were triglycerides (TAG) and free sterols plus diglycerides (FS+DAG), whereas the polar lipids were dominated by phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol plus ceramideaminoethanol phosphonate (PI+CAEP). An increase of the algal feeding ration resulted in an increase of the lipid content of spat which was associated with a significant augmentation of the TAG level (as percentage of the total lipids and as percentage of the neutral lipids). Lipid supplementation evoked a similar though more pronounced effect. Starvation resulted in a significant decline of the lipid content and a complete depletion of the TAG reserve. Contrary to the neutral lipids (NL), the relative proportion (percentage of total polar lipids, PL) of the individual PL classes was hardly affected by the diet. The importance of lipid and TAG reserves in early juveniles is discussed. Received: 15 October 1999 / Accepted: 15 February 2000     

Chemical characterization of contact semiochemicals for host-recognition and host-acceptance by the specialist parasitoid <Emphasis Type="Italic">Cotesia plutellae</Emphasis> (Kurdjumov)

Summary. Cotesia plutellae is a specialist parasitoid of Plutella xylostella. This specificity is potentially under the control of several factors before and after oviposition. Thereby, the stimuli that lead female parasitoids to host locations and to oviposition, might be at the basis of the specificity. We explore here the response of C. plutellae females exposed to host cuticular lipids. A total cuticular lipid extract of host caterpillars was fractionated into a hydrocarbon fraction and a non-hydrocarbon fraction. Neither fraction alone had any effect on oviposition behaviour in C. plutellae but the hydrocarbon fraction alone did seem to have a positive effect on the rate of antennal contact by the females. To induce oviposition behaviour, both fractions were necessary and reflect cooperation between at least one compound in each fraction. Identification of cuticular lipids shows that hydrocarbons were dominant (77%). Non-hydrocarbon compounds were mainly represented by 15-nonacosanone (18% of the total lipid extract). This ketone is rare in insect cuticle lipids and is thought to originate from the cabbage epicuticle where it is dominant with n-C₂₉ and 14- and 15-nonacosanol also found among the cuticular lipids of the host caterpillar.     

Histological and histochemical alterations induced by lead in the liver of the quail Coturnix coturnix

Adult males of the quail Coturnix coturnix were exposed to lead acetate trihydrate in drinking water (0.1, 0.25, 0.5, and 1% for one–six months) to investigate histological and histochemical alterations induced by lead intoxication in the liver. Chronic exposure to subtoxic concentrations of lead produced changes in hepatocytes, portal veins, Kupffer cells, and blood sinusoids. Alterations in hepatocytes mainly involved cytoplasmic vacuolation, necrosis, cytolysis, and glycogen accumulation. Kupffer cell hyperplasia, hemosiderosis, blood sinusoidal dilatation, portal vein congestion, and edema were also observed. No fibrosis or cirrhosis in the liver of any member of the dose groups over the entire period of the study was noted. The findings revealed that chronic exposure to lead produced mild histological and histochemical changes in the liver of the quail Coturnix coturnix.     

Fish-bone oil: Percent total body lipid and carbon-14 uptake following feeding of 1-14C-palmitic acid

Bones contain the majority of body lipid in some marine fish. In the sheepshead wrasse Pimelometopon pulchrum and the sablefish Anoplopoma fimbria, the bone lipid comprised 79 to 93% and 52 to 82% of the total body lipid, respectively. The senorita Oxyjulus california, another species of wrasse, has only 14% of its body lipid in bone. To determine whether dietary lipid is deposited quickly in the bone lipid, three species of fish were fed 1-¹⁴C-palmitic acid. Radioactivity appeared in the bone lipid as soon as 12 h after feeding, with the species rich in bone lipid incorporating the highest activity relative to the flesh. Roughly 80% of the radioactivity recovered in A. fimbria bone lipid was found in triglyceride. Radioactivity was equally distributed between phospholipid and triglyceride in P. pulchrum bone lipids. The results suggest that in some marine fish the bones contain the majority of the organism's reserve energy.     

Lipids and fatty acids as indicators of egg condition,larval feeding and maternal effects in Cape hakes (<Emphasis Type="Italic">Merluccius paradoxus</Emphasis> and <Emphasis Type="Italic">M. capensis</Emphasis>)

Cape hakes, Merluccius paradoxus and M. capensis, are important gadoid fish that are commercially harvested in the Benguela Current system off Namibia and South Africa. The aim of this study was to elucidate the nutritional condition and feeding preferences of their larvae. Hake eggs and larvae were sampled in austral spring of two consecutive years, 2007 and 2008, off the west coast of South Africa. They were identified to species using genetics, and total lipid content and fatty acid (FA) composition were analysed for each individual egg and larva to compare the condition of different early life stages of both hake species. Higher abundances of M. paradoxus eggs and larvae were consistently found compared to M. capensis. In both species, eggs contained wax esters (WE) and had significantly higher lipid content per dry mass than larvae. Lipid content as well as FA composition changed with the developmental stage of larvae. Quantities of essential fatty acid (EFA) increased with feeding of larvae due to dietary lipid incorporation. In 2007, yolk-sac larvae contained significantly lower total lipids than in 2008. It is argued that this was due to reduced lipid transfer by the spawning females to the eggs. These findings indicate that maternal effects are important in determining condition of hake larvae and that this may have an effect on their survival and subsequent recruitment.     

Interaction of short-term testosterone treatment with osmotic acclimation in the gilthead sea bream <Emphasis Type="Italic">Sparus auratus</Emphasis>

To assess the interaction between testosterone (T) treatment and acclimation to different salinities, seawater-acclimated gilthead sea bream (Sparus auratus) were implanted with slow-release coconut oil implants alone (control) or containing T (5 μg/g body mass). After 5 days, eight fish of control and T-treated groups were sampled. The same day, eight fish of each group were transferred to low salinity water (LSW, 6 ppt, hypoosmotic test), seawater (SW, 38 ppt, control test) and high salinity water (HSW, 55 ppt, hyperosmotic test) and sampled 9 days later. Gill Na⁺, K⁺-ATPase activity increased in HSW-acclimated fish with respect to SW- and LSW-acclimated fish in both control and T-treated groups. Kidney Na⁺, K⁺-ATPase activity was also enhanced in HSW-acclimated fish, but only in T-treated group. From a metabolic point of view, most of the changes observed can be attributed to the action of salinity and T treatment alone, since few interactions between T treatment and osmotic acclimation to different salinities were observed. Those interactions included in treated fish: in the liver, decreased capacity in using glucose in fish acclimated to extreme salinities; in the gills, decreased capacity in using amino acids in HSW; in the kidneys increased capacity in using amino acids in extreme salinities; and in the brain, decreased glycogen and acetoacetate levels of fish in LSW.     

Comparison of cellular and molecular cytotoxic mechanisms of Cochlodinium polykrikoides in isolated trout and rat hepatocytes

Harmful algal blooms produced by the marine ichthyotoxic dinoflagellate Cochlodinium polykrikoides are responsible for mass mortalities of wild and farmed fish globally. This study compared the cytotoxic mechanisms of C. polykrikoides total extract on both trout and rat liver hepatocytes. Trout hepatocytes were more sensitive than rat hepatocytes against C. polykrikoides extract. The effective concentration 50 after 3 hour incubation (EC50_3hr) concentrations found for C. polykrikoides extract in trout and rat hepatocytes (i.e., 50% membrane lysis in 3 hr) were Eq. 1 cell/ml and Eq. 240 cell/ml, respectively. C. polykrikoides extract exposure in both isolated trout and rat hepatocytes resulted in membrane lysis, reactive oxygen species formation, glutathione depletion, collapse of mitochondrial membrane potential, ATP depletion, increase in adenosine diphosphate (ADP)/adenosine triphosphate (ATP) ratio, cytochrome c release into the hepatocyte cytosol, and activation of caspases cascade. Trout hepatocyte toxicity was also associated with lysosomal membrane injury. Mitochondrial permeability transition in both trout and rat hepatocytes produced cytochrome c release from the mitochondrial intramembrane space into the cytosol. Thus, the cytochrome c release triggered activation of caspase-3 and apoptosis. Finally, data demonstrated that C. polykrikoides extract may induce more apoptotic phenotype in rat than trout hepatocytes, which in the latter favored predominantly necrotic mode of cell death.     

Changes in biochemical and fatty acid composition of the razor clam <Emphasis Type="Italic">Solen marginatus</Emphasis> (Solenidae: Bivalvia) during larval development

Aquaculture studies have revealed that polyunsaturated fatty acids are critical for maintaining substantial growth, survival and reproductive rates, and high food conversion efficiencies for a wide variety of marine and freshwater organisms. The aim of this study was to investigate the gross biochemical and fatty acid composition of both neutral and polar lipid compartments of the razor clam Solen marginatus throughout embryonic and larval development. High levels of stored reserves in S. marginatus eggs allow a short larval development, lasting only 8 days. The energy required for embryogenesis was obtained from stored proteins. During larval development from D-shaped veliger until settlement, protein, lipid, and carbohydrate reserves were indistinctly stored for metamorphosis. Although total lipids increased, fatty acids in both neutral and polar lipids decreased during embryonic development. The depots allow a short larval development in which settlement is reached with lower amounts of stored neutral and polar lipids than the contents found in the oocytes. Non-methylene-interrupted dienoic fatty acid levels were similar to those of some polyunsaturated fatty acids, with increasing percentages at the onset of metamorphosis. This study indicates that S. marginatus exhibits a different pattern in the use of gross biochemical and fatty acid reserves during larval development compared to other razor clam and bivalve species, mainly due to the large size of its eggs and the short larval development stage reported in this species.     

Biochemical changes during the reproductive cycle of the deep-sea decapod <Emphasis Type="Italic">Nephrops norvegicus</Emphasis> on the south coast of Portugal

The objectives of the present study were to characterize the changes in the proximate chemical composition, lipid classes, fatty-acid profiles, glycogen and cholesterol contents of the muscle, ovary and hepatopancreas of Nephrops norvegicus (L.), during the reproduction cycle of this species. The gonadosomatic index increased significantly in May and June and during maturation, suggesting that spawning may start in late spring or summer. The hepatosomatic index also increased throughout the ovarian maturation, suggesting that the hepatopancreatic resources are not depleted. Positive correlations between lipid levels in the ovary and the gonadosomatic index (r=0.51, P<0.05) and the hepatopsomatic index (r=0.27, P<0.05) were found. In fact, ovarian lipid levels increased with maturation, but no concomitant decrease occurred in hepatopancreatic lipids. The muscle showed very low lipid levels (mainly polar lipids), presenting a significant increase during May and June (P<0.05). Higher proportions of neutral lipids, mainly triacylglycerols, were observed in the ovary and the hepatopancreas. Since both ovarian and hepatopancreatic cholesterol increased with maturation, the mobilization of hepatopancreatic cholesterol stores to build up ovarian cholesterol was not clear. On the other hand, protein and glycogen contents in the muscle, ovary and hepatopancreas did not vary as a function of ovary maturity stage. Among the various tissues analysed, the glycogen was mainly stored in the hepatopancreas and to a lesser extent in the muscle. In both ovary and hepatopancreas the major fatty acids were 16:0, 18:1(n-7), 18:1(n-9), 20:5(n-3) and 22:6(n-3), and significant increases (P<0.05) in the levels of monounsaturated and polyunsaturated fatty acids were observed in the ovary during sexual maturation, which indicates these compounds are the major sources of energy during embryonic and early larval development. It was evident that reproduction has profound effects upon the biochemistry of this species, because there are large associated energy costs, owing to the increase in biosynthetic work, which will support the lecithotrophic strategy of the embryos and first larval stages.