Changes in metabolism and hepatic ultrastructure induced by estradiol and testosterone in immature female Epinephelus akaara (Teleostei,Serranidae)

Summary Estradiol injections increase serum level of calcium, amino acid, glucose, protein, ammonia and creatinine in immature Epinephelus akaara, and also increase levels of total lipid, cholesterol, phospholipid and esterified fatty acids. Hepatic protein, glycogen and lipid concentrations also rise after estradiol treatment, and some hepatic enzymes participating in the metabolism of nitrogen, lipid and carbohydrate, show increased activity. Serum vitellogenin levels are increased. Testosterone treatment increases serum protein, total lipid, cholesterol, amino acid and ammonia levels, and also hepatic glycogen content, but in contrast to estradiol treatment, testosterone does not change serum vitellogenin, glucose, calcium, phospholipid, esterified fatty acid and creatinine levels, nor the hepatic lipid and protein content. A small number of hepatic enzymes shows an increased activity. Vitellogenic fish show biochemical changes similar to that of estradiol-treated fish, but are different from those of immature fish. Estradiol treatment induces ultrastructural changes in the hepatocytes of immature fish that are similar to those found in vitellogenic fish. These include a proliferation of rough endoplasmic reticulum and Golgi apparatus, and an increase in glycogen and lipid, all indicative of enhanced metabolic activity.     

Effect of water temperature and dietary starch on growth and metabolic utilization of diets in gilthead sea bream (Sparus aurata) juveniles

We evaluated the effect of dietary starch level on growth performance, feed utilization, whole-body composition and activity of selected key enzymes of intermediary metabolism in gilthead sea bream juveniles reared at 18 and 25 degrees C. A diet was formulated to contain 48% crude protein, 12% lipids and 30% gelatinized maize starch (diet 30GS). Two other diets were formulated to include the same level of ingredients as diet 30GS except for the gelatinized starch, which was included at 20% (diet 20GS) or 10% (diet 10GS). No adjustment to diet composition was otherwise made. Each diet was fed to triplicate groups of gilthead sea bream (30 g initial mass) for 8 weeks, on a pair-feeding scheme. The higher temperature improved growth performance but the opposite was true for feed efficiency and protein efficiency ratio. Independently of temperature, growth performance, feed efficiency and protein efficiency ratio were lower in fish fed diet 30GS. No effect of temperature or dietary starch level on whole-body composition was noticed. Hepatosomatic index and liver glycogen were higher at 18 degrees C and, within each temperature, in fish fed diet 30GS. Glycemia was not affected by temperature, but was lower in fish fed diet 10GS. Data on enzyme activities showed that increasing water temperature enhances liver glucokinase (GK) and pyruvate kinase (PK) activities, suggesting that gilthead sea bream is more apt to use dietary starch at higher temperatures. No effect of temperature was noticed on hexokinase (HK), fructose-1,6-bisphosphatase (FBPase), glucose-6-phosphate dehydrogenase (G6PD) and glutamate dehydrogenase (GDH) activities. Dietary starch enhanced PK and FBPase activities while depressed GDH activity, suggesting a lack of significant regulation of hepatic glucose utilization and production in this species. HK, GK and G6PD activities were unaffected by dietary composition. Irrespectively of water temperature, gelatinized starch may be included up to 20% in diets for gilthead sea bream juveniles; at higher dietary levels, growth and efficiency of feed utilization are depressed.     

Effects of dietary protein and lipid levels on growth and feed utilization of wild‐caught striped sea bream,Lithognathus mormyrus

A feeding trial was carried out to determine the effects of dietary protein and lipid levels on the growth performance and feed utilization of wild‐caught striped sea bream (Lithognathus mormyrus). The experimental fish were collected from a local lagoon (Çardak Lagoon, Çanakkale, Turkey), transferred to the Marine Net Cage Unit and fed by hand to apparent satiation with a commercial sea bream feed (Biomar; 42% crude protein, 16% crude lipid). Approximately 4 weeks were needed to acclimate the fish to farming conditions. No pathological signs were observed and no fish losses occurred during the adaptation period. For the test trials four test diets with different levels of protein and lipid were formulated [low protein and low lipid (LP:LL), low protein and high lipid (LP:HL), high protein and low lipid (HP:LL), and high protein and high lipid (HP:HL)] and fed to L. mormyrus (mean weight 85.0 ± 4.6 g SEM) in the net cages (Ø 2 m, depth 2.5 m) for 60 days. During the experiment water temperature varied between 21.1 and 26.4°C; dissolved oxygen 8.4–9.6 mg L^?1; pH 7.2–8.6; and salinity 23.3–25.6‰. Growth performances of fish fed high protein diets were higher compared to fish fed low protein diets, irrespective of the dietary lipid level (P < 0.05). Feed conversion ratio (FCR) and protein efficiency ratio (PER) were not influenced by dietary protein or lipid levels (P > 0.05). Preliminary results indicate that striped sea bream can be easily adapted to farming conditions in net cages, and that a diet containing 50% crude protein and 15% crude lipid (HP:LL) levels with 23.0 g protein MJ^?1 gross energy of protein/energy ratio would be suitable for striped sea bream growth.     

A pharmacological dose of 17 β-oestradiol produces minimal metabolic stimulation but evokes hepatic necrosis in the immature female serranid Epinephelus akaara

A pharmacological dose of 17β-oestradiol (5 mg kg⁻¹ per injection for a total of five injections over a period of 9 days) increased liver and serum lipid concentration and induced vitellogenin into the serum of the immature female red grouper Epinephelus akaara . The levels of electrolytes, glucose, lactate and protein in the serum, and the protein, glycogen and water content of liver and muscle were not affected. The activities of enzymes regulating gluconeogenesis, glycolysis, Krebs cycle, transamination and glycogen synthesis remained unaltered. These findings are in marked contrast to those of Ng et al . (1984) which showed a strong stimulatory effect of a ten-times smaller dose of 17β-oestradiol on these biochemical parameters. Ultrastructural examination of hepatocytes of these heavily oestrogenized fish revealed that some cells possessed organelles with an abnormally activated appearance while others had undergone necrotic changes, suggesting that some hepatocytes were overstimulated and subsequently degenerated. Results of the present investigation caution against the use of a pharmacological dose of 17β-oestradiol in fish culture.     

Some macromolecular abnormalities developed by the interaction of malathion and permethrin and subsequent refeeding in Tribolium castaneum larvae

The effects of sublethal treatments of malathion and malathion + permethrin combinations on activities of acetylcholine esterase (ChE), carbohydrate-metabolizing enzymes (amylase; lactate dehydrogenase, LDH), protein-metabolizing enzymes (alanine and aspartate aminotransferase, ALAT, ASAT), as well as acid and basic phosphatases (AcP and AkP, respectively), and Kreb's cycle enzymes (isocitrate dehydrogenase, ICDH) were studied on sixth instar larvae of the red flour beetle, Tribolium castaneum. In addition, the levels of lipid, cholesterol, glucose, glycogen, proteins, free amino acids (FAA), urea, and nucleic acids (DNA and RNA) were determined. Malathion (400 ppm) increased the activity of LDH (53%), as well as the concentrations of FAA (31%) and urea (39%). Malathion treatments of 400 ppm decreased the glucose (20%) and glycogen (24%) content but did not affect other enzymes and biochemical components. Permethrin (200 ppm) and malathion (20 ppm) mixtures increased the activities of ChE (708%) and LDH (55%), and raised the concentrations of FAA (26%), urea (24%), glucose (23%), lipid (14%), cholesterol (21%), DNA (24%), and RNA (8%). The decrease in AcP activity and in glycogen concentration observed with malathion was sustained by permethrin in the mixture. Permethrin + malathion mixtures also depressed the levels of AkP (30%), ICDH (24%), and glycogen (36%). The intensity of effects commensurated with the dose and duration of insecticide exposure. Refeeding showed tendencies towards normalization of various biochemical parameters.     

Tolerance of Pomacanthus imperator to hypoosmotic salinities: changes in body composition and hepatic enzyme activities

Emperor angel fish Pomacanthus imperator were acclimated to various salinities (33, 22, 15, 10 and 7%) for 1 month and changes in serum chemistry, body composition and liver enzyme activities were monitored. No mortality was observed in fish adapted throughout the salinity range of 7–33% and the limit of survival was around 5%. Serum Na^+; and Cl ^– exhibited a stepwise decrease as the salinity was reduced from 33–7% but no concomitant tissue hydration could be observed. Branchial Na-K-ATPase activity was generally higher in hypoosmotic (7–15%) than in hyperosmotic salinities (22–33%o). Serum concentrations of glucose, lipid, α-amino acids and protein as well as the haematocrit value were all elevated in the salinity range of 15–22%. Serum cortisol was markedly lower but serum thyroxine was significantly elevated at 15–22%. Fish adapted to 15–22% had higher hepatosomatic indices, liver glycogen and muscle lipid contents and hepatic glucose-6-phosphate dehydrogenase activity. These data indicate that Pomacanthus imperator is a' physiologically euryhaline' species and metabolism in isoosmotic salinities has been fundamentally re-organized to favour carbohydrate and lipid retention.     

GLYCOGEN METABOLISM AND CHANGES IN THE ACTIVITIES OF PHOSPHORYLASE, PHOSPHOFRUCTOKINASE AND PYRUVATE KINASE DURING DEVELOPMENT OF SEA URCHIN EGGS

The glucose and glycogen contents of sea urchin eggs and embryos were measured enzymatically. Unfertilized eggs of Hemicentrotus pulcherrimus and Anthocidaris crassispina contain about 20.9 and 24.4 μg of glycogen per mg protein, respectively. As for glucose, unfertilized eggs of Hemicentrotus and Anthocidaris contain about 0.7 and 1.9 μg per mg protein, respectively. Glycogen consumption during embryonic development differs with different species of sea urchins. In Anthocidaris , glycogen decreases significantly after fertilization. The oxidation of glucose and glycogen accounts for about 50% of oxygen consumed until the early blastula stage in this species. The contribution ratio of glucose and glycogen to the overall energy pool becomes less than 10% at later stages. In Hemicentrotus , however, the glycogen content remains unchanged until the early blastula stage and thereafter decreases. The importance of glucose and glycogen as an energy fuel seems little throughout the development of Hemicentrotus. Activities of phosphorylase (EC 2.4.1.1), phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40) were measured at various embryonic stages in both species of sea urchins. The difference between two species in the consumption of glucose and glycogen can not be elucidated by the differences in the activities of these enzymes.     

The effects of 2-bromopalmitate on the fatty acid composition in differentiating adipocytes of red sea bream (Pagrus major)

To determine whether external factors affect the adipogenic function of fish adipocytes, the effects of 2-bromopalmitate (a PPAR agonist) on the fatty acid composition in differentiating adipocytes of red sea bream were investigated in vitro. In the presence of 2-bromopalmitate, the red sea bream adipocytes were differentiated and the effects on the fatty acid composition and the adipogenic gene expression were analyzed. With the level of 2-bromopalmitate, the content of 16:1n-7, a delta-9 desaturation product, increased in association with the increase in a stearoyl CoA desaturase (SCD) gene expression level while the triglyceride accumulation was not affected. Subsequently, the effects on the bioconversion of the n-3 and n-6 fatty acids, which are main series of dietary essential fatty acids, were examined. In the presence of 300 μM of 18:3n-3 or 18:2n-6, red sea bream stromal-vascular cells accumulated the lipid in the cytoplasm within 3 days by the fatty acid uptake with the increase of corresponding fatty acid contents. Furthermore, in both the 18:3n-3 and 18:2n-6 stored cells, the products of delta-6 desaturation (18:4n-3 and 18:3n-6, respectively) and C_18–20 elongation (20:3n-3 and 20:2n-6, respectively) were detected. However, neither the delta-6 desatutration nor C_18–20 elongation of 18:3n-3 and 18:2n-6 were enhanced by 2-bromopalmitate treatment. In conclusion, the results indicate that the adipocyte function in fish, e.g. adipogenic gene expression and fatty acid composition, can be modified by external factors and a main effect of 2-bromopalmitate is the increase in the content of delta-9 desaturation product by stimulating the SCD gene expression.     

Effect of α-tocopherol on doxorubicin induced alterations in glucose metabolism—A pilot study

The effect of doxorubicin on glucose metabolism was studied in rats with or without the supplementation of α-tocopherol. Rats were treated with doxorubicin, 2 mg/kg body wt. (intravenously), twice a week, for 6 weeks. α-Tocopherol (400 mg/kg body wt.) was co-administered orally for 2 months. Glycolysis was found to be increased with a significant decrease in the activities of tricarboxylic acid cycle enzymes. A significant increase in liver glycogen was noted in doxorubicin treated rats. Activities of glycogen Phosphorylase, glucose-6-phosphate dehydrogenase and glucose-6-phosphatase were found to be decreased. α-Tocopherol co-administration was found to reduce the alterations in the above mentioned enzyme activities. The results are discussed with reference to the drug metabolism, lipid peroxidation and the antioxidant nature of α-tocopherol.     

Influence of dietary amino acid profiles on growth performance and body composition of juvenile grouper Epinephelus coioides

A feeding experiment was conducted to investigate the effects of dietary amino acid (AA) profiles on growth performance and body composition of juvenile grouper Epinephelus coioides (initial mean weight: 68.1 ± 1.0 g, mean ± SD). Five diets contained 30% fishmeal, 12% soy protein concentrate and 20% crystalline amino acids (CAAs); the control diet contained 54% fishmeal and 17% soy protein concentrate as intact protein sources. CAAs were added to the five diets to simulate the AA pattern found in white fishmeal protein (WFP), brown fishmeal protein (BFP), hen egg protein (HEP), grouper E. coioides juvenile protein (GJP) and red sea bream egg protein (REP), respectively. The highest WG and SGR were obtained in fish fed the control diet, followed by fish fed the diets with AA profiles of WFP and GJP. Fish fed the diets with AA profiles of BFP, REP and HEP showed relatively poor growth performance. Feed utilization showed a similar trend in growth parameters. Protein content of whole body among these treatments showed no significant differences (P > 0.05), but lipid content of whole body showed the highest value in the control group (P < 0.05). Dietary AA profiles significantly influenced plasma protein, cholesterol, triacylglycerol and glucose concentrations (P < 0.05). Dietary AA profiles significantly influenced the condition factor, hepatosomatic index and intraperitoneal fat ratio (P < 0.05).     

The sequential restoration of plasma metabolite levels,liver composition and liver structure in refed carp,Cyprinus carpio

Effect of realimentation was studied on the structure and function of liver tissue of carp,Cyprinus carpio. Yearling carp, after a 3-month starvation period, were renourished at a feeding rate of 1% body weight per day. Samples were taken at refeeding days 0, 1, 2, 5, 22 and 78. Analyses were made of blood metabolites, liver RNA, DNA, lipids, glycogen and protein and of liver enzyme activities. Additionally, liver cytology was examined by means of qualitative and quantitative electron microscopy. The early refeeding period (up to day 5) was characterized by a fast recovery of plasma metabolite concentrations (protein, total lipids, free fatty acids, glucose), a drastic augmentation of hepatic glycogen reserves, and a pronounced increase of total liver weight and liver-somatic index. Constant values of total hepatic DNA showed that liver weight augmentation was not due to cell proliferation, but to a pronounced enlargement of the existing hepatocytes. Major hunger-related structural modifications of carp hepatocytes such as enlarged mitochondria or prominence of the lysosomal compartment were reversed. A significant volume increase of cell nuclei, together with a particularly strong elevation of hepatic RNA concentrations during initial realimentation suggest an immediate stimulation of protein synthesis. Since the cisternae of the endoplasmic reticulum were not reconstituted during that early phase, protein synthesis may have been executed mainly by free ribosomes. With prolonged realimentation, the volume of the endoplasmic reticulum as well as total and relative contents of liver soluble protein continuously increased, whereas RNA concentrations decreased again. An enforcement of liver oxidative capacity was indicated by the augmentation of cellular number and volume of mitochondria. The activities of the enzymes glucose-6-phosphate dehydrogenase and malic enzyme, which convert excess energy into NADPH, increased steadily. Concomitantly, hepatic lipid accumulation was enhanced. In conclusion, liver metabolism during the early recovery phase seems to be dominated both by repair processes and by intensive protein and glycogen synthesis. The liver slows down these processes during prolonged refeeding and directs an increasing percentage of energy and metabolites toward the generation of reducing equivalents and lipid reserves.Abbreviations BW body weight - ER endoplasmic reticulum - FFA free fatty acids - G6PDH glucose-6-phosphate dehydrogenase - LSI liver somtic index - LW liver weight - ME malic enzyme Presented in part as poster abstract at the International Congress on Research in Aquaculture: Fundamental and Applied Aspects. Antibes, France, 6–10 October, 1991     

Intrauterine Malnutrition and the Brain: Effects on Enzymes and Free Amino Acids Related to Glutamate Metabolism

Abstract: The effect of feeding pregnant rats with wheat and Bengal gram (black chick pea) diets during the later part of pregnancy on brain growth, enzymes, and free amino acids of glutamate metabolism in 1-day-old rats was investigated. These diets did not induce growth dissociation, and the body and brain weights were equally affected. The concentrations of DNA, RNA, protein, and free α-amino nitrogen in brain decreased significantly and the activities of glutamine synthetase, glutamine transferase, glutaminase 1, glutaminase 11, and glutamate decarboxylase and the concentrations of free amino acids, glutamic acid, glutamine, alanine, and GABA were also decreased. The concentration of aspartic acid, however, was increased. Wheat and Bengal gram diets fortified with lysine and with methionine, cystine, and tryptophan respectively showed various beneficial effects on the changes observed in the brain. A 20% casein diet induced higher body and brain weights and better brain protein and free α-amino nitrogen concentrations than those observed on a 10% casein diet.     

Evaluation of the rate-limiting steps in the pathway of glucose metabolism in kidney cortex of normal, diabetic, cortisone-treated and growth hormone-treated rats

1. The activities of gluconeogenic and glycolytic enzymes and the concentrations of citrate, ammonia, amino acids, glycogen, glucose 6-phosphate, acetyl-CoA, lactate and pyruvate were measured in kidney cortex of normal, diabetic, cortisone-treated and growth hormone-treated rats. 2. In kidney cortex of diabetic, cortisone-treated and growth hormone-treated rats the activities of glucose 6-phosphatase (EC 3.1.3.9), fructose 1,6-diphosphatase (EC 3.1.3.11) and phosphopyruvate carboxylase (EC 4.1.1.32) were increased. 3. The activities of glutamate dehydrogenase (EC 1.4.1.3), alanine aminotransferase (EC 2.6.1.2), aspartate aminotransferase (EC 2.6.1.10) and pyruvate carboxylase (EC 6.4.1.1) were increased in diabetic and cortisone-treated rats. In growth hormone-treated rats the activity of aspartate aminotransferase was depressed but those of the other three enzymes were unchanged. 4. The activity of hexokinase (EC 2.7.1.1) was not altered in any of these conditions. Phosphofructokinase (EC 2.7.1.11) activity was depressed only in growth hormone-treated rats. Pyruvate kinase (EC 2.7.1.40) activity was depressed in cortisone-treated and growth hormone-treated rats but unchanged in diabetic rats. 5. Amino acids, acetyl-CoA and glucose 6-phosphate contents were increased in rat kidneys in all these three conditions. Ammonia content was increased in diabetic and cortisone-treated rats but was markedly diminished in growth hormone-treated rats. 6. The [lactate]/[pyruvate] ratio was elevated in diabetic and cortisone-treated rats but unchanged in growth hormone-treated rats. Citrate content was increased in the kidney cortex of diabetic and growth hormone-treated rats but was unchanged in cortisone-treated rats. The activity of ATP citrate lyase (EC 4.1.3.8) was depressed in diabetic and growth hormone-treated rats but was increased in cortisone-treated rats. 7. Glycogen content was moderately elevated in growth hormone-treated rats and markedly elevated in diabetic rats, whereas no change in glycogen content was observed in cortisone-treated rats. Glycogen synthetase (EC 2.4.1.11) activity was unchanged in all these three conditions. Phosphorylase (EC 2.4.1.1) activity was not affected in cortisone-treated rats but was depressed in diabetic and growth hormone-treated rats.     

Organization of the lipoprotein lipase gene of red sea bream Pagrus major

Lipoprotein lipase (LPL) is a key enzyme of lipid deposition and metabolism. To investigate the mechanism of lipid deposition in fish, as a first step, we have characterized the LPL gene of a marine teleost red sea bream Pagrus major by cDNA and genomic structure analysis. The red sea bream LPL gene encodes 511 amino acids and spans approximately 6.3 kb of the genome. The coding region is organized into ten exons and nine introns. In comparison with the LPL of other animals, the deduced amino acid sequence shows a high degree of similarity with a conservation of functional domains, e.g. catalytic triad, N-glycosylation sites, lipid and heparin binding regions. The 1.1 kb of 5′ flanking region contains two CCAAT, sequences homologous to Oct-I site and response elements for hormones including glucocorticoid, insulin and thyroid hormone. The results of the present study will facilitate further study of the function and regulation of the LPL in non-mammalian vertebrates.     

Purification and characterization of three isoforms of chrysophsin, a novel antimicrobial peptide in the gills of the red sea bream, Chrysophrys major.

We report here the isolation of three isoforms of a novel C-terminally amidated peptide from the gills of red sea bream, Chrysophrys (Pagrus) major. Peptide sequences were determined by a combination of Edman degradation, MS and HPLC analysis of native and synthetic peptides. Three peptides, named chrysophsin-1, chrysophsin-2, and chrysophsin-3, consist of 25, 25, and 20 amino acids, respectively, and are highly cationic, containing an unusual C-terminal RRRH sequence. The alpha-helical structures of the three chrysophsin peptides were predicted from their secondary structures and were confirmed by CD spectroscopy. The synthetic peptides displayed broad-spectrum bactericidal activity against Gram-negative and Gram-positive bacteria including Escherichia coli, Bacillus subtilis, and fish and crustacean pathogens. The three peptides were also hemolytic. Immunohistochemical analysis showed that chrysophsins were localized in certain epithelial cells lining the surface of secondary lamellae and eosinophilic granule cell-like cells at the base of the secondary lamellae in red sea bream gills. Their broad ranging bactericidal activities, combined with their localization in certain cells and eosinophilic granule cell-like cells in the gills, suggest that chrysophsins play a significant role in the innate defense system of red sea bream gills.     

New insights into fish swimming: a proteomic and isotopic approach in gilthead sea bream

Moderate exercise enhances fish growth, although underlying physiological mechanisms are not fully known. Here we performed a proteomic and metabolic study in white (WM) and red (RM) muscle of gilthead sea bream juveniles swimming at 1.5 body lengths per second. Continuous swimming for four weeks enhanced fish growth without increasing food intake. Exercise affected muscle energy stores by decreasing lipid and glycogen contents in WM and RM, respectively. Protein synthesis capacity (RNA/protein), energy use (estimated by lipid-δ(13)C and glycogen-δ(13)C), and enzymatic aerobic capacity increased in WM, while protein turnover (expressed by δ(15)N-fractionation) did not change. RM showed no changes in any of these parameters. 2D-PAGE analysis showed that almost 15% of sarcoplasmic protein spots from WM and RM differed in response to exercise, most being over-expressed in WM and under-expressed in RM. Protein identification by MALDI-TOF/TOF-MS and LC-MS/MS revealed exercise-induced enhancement of several pathways in WM (carbohydrate catabolism, protein synthesis, muscle contraction, and detoxification) and under-expression of others in RM (energy production, muscle contraction, and homeostatic processes). The mechanism underpinning the phenotypic response to exercise sheds light on the adaptive processes of fish muscles, being the sustained-moderate swimming induced in gilthead sea bream achieved mainly by WM, thus reducing the work load of RM and improving swimming performance and food conversion efficiency.     

Effect of starvation on tissue and serum gluconeogenic enzymes, alkaline phosphatase and tissue glycogen in the freshwater catfish, Heteropneustes fossilis (Bloch).

The influence of starvation has been studied on tissue and serum G-6Pase F-D-Pase and alkaline phosphatase activities and on the muscle and liver glycogen content of the freshwater catfish H. fossilis (Bloch). A marked increase in G-6Pase and F-D-Pase activities and a fall in the muscle and liver glycogen content recorded during 40 day starvation. The rise in gluconeogenic enzymes during starvation may be due to glucocorticoid stimulation. Alkaline phosphatase activity was found to decline markedly during starvation. The decline in enzyme activity is attributed to some factors like a fall in the rate of synthesis caused by lowered metabolic demands and to electrolyte imbalance caused by tissue overhydration. The fall in glycogen content may be related to the starved condition of the fish. Elevation in glycogen content and alkaline phosphatase activity and a fall in gluconeogenic enzymes were noted when feeding had been resumed.     

Metabolic and osmoregulatory changes in response to reduced salinities in the red grouper, Epinephelus akaara (Temminck & Schlegel), and the black sea bream, Mylio macrocephalus (Basilewsky)

Red groupers (Epinephelus akaara Temminck & Schlegel) and black sea breams (Mylio macrocephalus Basilewsky) were transferred from 30‰ into 3, 7, 12, 20, and 30‰ salinity. Fish were sampled at 0, 6, 24, 96, 168 and 336h after transfer. Serum osmolality, glucose, protein, Na⁺, K⁺, Ca²⁺, liver glycogen, liver protein, muscle water and haematocrit were determined. In general, transient disturbances in these variables were observed after transfer. For both species, no tissue hydration was observed upon acclimation to different salinities, whereas a progressive increase in haematocrit value was found as salinity decreased. Liver glycogen of both species, however, was higher in hypo-osmotic salinities. Serum Na⁺ of the red groupers declined upon acclimation to 7‰ salinity but the opposite was found for the black sea breams. The results indicate that both species are extremely euryhaline, and physiological stress is unlikely to occur within the salinity regime of 7 to 30‰ Comparatively, the black sea bream appears to be a more efficient osmoregulator.     

Growth,pigments, and biochemical composition of marine red alga Gracilaria crassa

The marine red alga Gracilaria crassa was investigated for its proximate composition, minerals, fatty acids, amino acids, and agar content to decipher its nutritional implications. The growth performance and pigments were studied under different combinations of temperature and salinity. On a dry weight basis the total lipid content was 1.30?±?0.05 %, protein was 5.18?±?0.64 %, carbohydrate was 42.0?±?1.2 %, ash was 43.18?±?1.15 %, and agar content was 21.52?±?0.73 %. Appreciable amounts of macro-, micro-nutrients (K?>?Na, Ca, Mg, and Fe), and essential amino acids (Ileu, His, Thr, Leu, and Lys) were found. Palmitic, stearic acid, and arachidonic acid were major fatty acids detected. The alga showed maximum daily growth rate (DGR %) 5.8?±?0.09 % at 25 °C, 35 ‰ salinity. The highest content of pigment R-phycoerythrin (444.7?±?1.9 μg g^?1 fresh weight (FW) basis) was obtained at 25 ‰ salinity at 35 °C while that of R-phycocyanin (476.3?±?2.3 μg g^?1 DW) at 30 ‰ salinity at 30 °C. This study revealed that this alga can be utilized as a potential source for food and feed. The data generated on best growth conditions will be very useful for farming of G. crassa in open sea. This alga could be used for production of natural colorants at defined control condition.     

A histochemical and immunohistochemical study of digestive enzymes and hormones during the larval development of the sea bream, Sparus aurata L.

Summary The distribution of different hydrolytic enzymes and the localization of the hormones which regulate glucose metabolism during development of the digestive tract of the sea bream, Sparus aurata L., were studied. The yolk sac contains trypsin, glucose-6-phosphatase, ATPases and acid and alkaline phosphatase activities. Positive insulin, glucagon and somatostatin cells were observed in the pancreas and in the lumen of the intestinal tract during endogenous feeding. From hatching until 3 days later, the digestive tract of sea bream larvae shows no enzymatic activities. During exogenous feeding, the activities of the phosphatases and trypsin generally increase, as do the amounts of the hydrolytic enzymes and trypsin, as well as the pancreatic and intestinal hormones. The enzymatic activities gradually decrease from the anterior part towards the posterior part of the digestive tract.