Showing papers in "Fish Physiology and Biochemistry in 1998"
TL;DR: Results strongly suggest that the enzyme purified from the hepatopancreas of red sea bream is homologous to mammalian bile salt-activated lipase.
Abstract: A lipase was purified from the extract of the delipidated powder of red sea bream hepatopancreas to nar homogeneity by fractional precipitation with ammonium sulfate and sequential chromatography on first anion-exchange-, hydrophobic- and second anion-exchange columns followed by gel filtration and anion-exchange HPLC. The final enzyme preparation showed a single band with an apparent molecular mass of approx. 64 kDa by sodium dodecyl sulfate-polyacrylamid e gel electrophoresis. The purified enzyme had a pH optimum in the range of pH 7.0–9.0. Using ρ-nitrophenyl myristate or triolein as a substrate, the enzyme required the presence of sodium taurocholate or sodium cholate for its activity. No activity was observed in the presence of sodium deoxycholate. The enzyme preferentially hydrolyzed ethyl esters of polyunsaturated fatty acid, such as arachidonic acid and eicosapentaenoic acid which were resistant to porcine pancreatic lipase. These results strongly suggest that the enzyme purified from the hepatopancreas of red sea bream is homologous to mammalian bile salt-activated lipase.
266 citations
TL;DR: This study shows for the first time that the molecular mechanisms which control the dietary adaptation of trypsin and amylase are independently regulated, age-dependent and influenced by the composition and the quantity of the diet.
Abstract: Specific activities and mRNA levels of trypsin and amylase were studied in sea bass larvae. From day 20 to day 40, Dicentrarchus labrax were fed two rations of one day old Artemia: satiation (LP) and one-eighth of the satiation ration (LP/8) or two isoenergetic compound diets that varied in protein (30 and 60%) and carbohydrate (37 and 7%) content (FP30 and FP60 respectively). Trypsin mRNA levels and specific activities were mainly influenced by the nature of dietary protein and the Artemia ration. By using fish meal as protein source, dietary protein concentration did not affect either mRNA level nor specific activity of trypsin. These results suggested that the trypsin synthesis was not affected at a transcriptional level by the protein ration, i.e., Artemia ration. Decrease in amylase mRNA observed from day 29 in the four dietary groups suggested that this decrease in amylase expression is genetically programmed during sea bass larvae development. Nevertheless, the composition and the quantity of the diet influenced the amylase specific activities revealing primarily translational regulation of amylase. This study shows for the first time that the molecular mechanisms which control the dietary adaptation of trypsin and amylase are independently regulated, age-dependent and influenced by the composition and the quantity of the diet.
191 citations
TL;DR: Results suggest that both a-tocopherol and n-3 HUFA nutritional deficiencies rather than stress are an important determinant of fish complement activity.
Abstract: Studies on the alternative complement pathway (ACP) activity in fish have suggested the particular relevance of this pathway as a non-specific immune mechanism being its activation directly related with the availability of certain nutrients In the present study ACP activity in gilthead seabream fed different dietary levels of a-tocopherol and n-3 HUFA deficiencies was studied under different stress conditions (overcrowding and repetitive chasing) A reduction in ACP activity was found when diets with deficiencies in α-tocopherol and n-3 HUFA were assayed at any of the experimental conditions assayed Levels of plasma cortisol were similar to those of fish after crowding stress subjected to dietary deficiencies at low stocking density, suggesting that dietary deficiencies produced a chronic elevation of cortisol When fish were subjected to repetitive chasing, plasma cortisol from fish fed control diet showed a progressive increase whereas plasma cortisol levels from both dietary deficient groups showed a transitory peak 4 days after the beginning of the repetitive chasing However, ACP activity levels of fish fed deficient diets remained lower than the control group and constant during chasing period These results suggest that both a-tocopherol and n-3 HUFA nutritional deficiencies rather than stress are an important determinant of fish complement activity
153 citations
TL;DR: Evidences support the existence of a more active and complex protease set in dentex, and important differences in total activity, as well as in thermal and pH stability were found.
Abstract: Digestive proteases present in two sparids, seabream (Sparus aurata) and common dentex (Dentex dentex), have been characterized using both biochemical and electrophoretic techniques. Although optimum pH and temperature for maximum activity of both acid and alkaline proteases were similar in the two species, important differences in total activity, as well as in thermal and pH stability were found. Specific inhibitors and SDS-PAGE zymograms were used to clarify such differences. Evidences support the existence of a more active and complex protease set in dentex. Results are discussed from the perspective of their application to the formulation of feeds for each species.
147 citations
TL;DR: In this paper, a radioimmunoassay analysis of the testes of mature and maturing male New Zealand freshwater eels was carried out to obtain data on the natural reproductive physiology of these fish.
Abstract: Immature and maturing male New Zealand freshwater eels, the shortfinned Anguilla australis and the longfinned A. dieffenbachii, were caught from the wild to obtain data on the natural reproductive physiology of these fish. Plasma samples were analysed for steroid hormones by radioimmunoassay and values related to the developmental stage of the testes. Our histological observations on testes largely confirmed those reported previously. Thus, the gonad of non-migrating eels often appeared undifferentiated or poorly developed, containing only type A or early type B spermatogonia. In contrast, the testes of migrating shortfins were in early spermatogenesis as evidenced by the presence of late type B spermatogonia. Similarly, early spermatogenic stages were common in migratory longfins, but eels in midspermatogenesis (all germ cell stages present) were also encountered. Unlike a previous study, patches of testicular regression were commonly seen in migrants of both species. Levels of several androgens, androstenedione (AD), testosterone and 11-ketotestosterone (KT), were elevated in migrants compared to non-migrants. AD was higher in early to midspermatogenic A. dieffenbachii (0.63 ng ml−1) than in A. australis (0.25 ng ml−1) in the spermatogonial proliferation stage, while the inverse was observed for KT (27.78 ng ml−1 and 50.52 ng ml−1, respectively). Levels of 17,20β-dihydroxy-4-pregnen-3-one were nearly undetectable (less than 0.12 ng ml−1) in all animals. Plasma 17-hydroxyprogesterone concentrations in fyke-caught eels were elevated to a greater extent in non-migrants (up to 1.92 ng ml−1) than in migrants (around 0.5 ng ml−1), and correlated well with levels of cortisol in all groups. Histological results are compared to previous studies and the presence of regression in the testes is discussed. In addition, the role of steroid hormones, in particular AD and KT, in reproduction and stress is considered.
141 citations
TL;DR: The results indicate that dietary fatty acid composition influenced swimming performance in Atlantic salmon through changes in maximum swimming speed (Ucrit), and it is suggested that metabolism of these 18-carbon unsaturated fatty acids accounts for the effects of the diets on exercise performance.
Abstract: Swimming performance was measured in Atlantic salmon (Salmo salar, L.) fed one of four isonitrogenous and isoenergetic experimental diets, in which the supplemental lipid (25% of diet) originated either solely from menhaden oil (rich in highly unsaturated fatty acids of the n-3 series; n-3 HUFA), or from different proportions of this oil and canola oil (rich in 18-carbon unsaturated fatty acids).
107 citations
TL;DR: In this paper, the absorption, excretion and requirement of dietary phosphorus (P) by Atlantic salmon (Salmo salar) were determined by using a four-parameter sigmoidal equation.
Abstract: Studies were conducted to determine the absorption, excretion and requirement of dietary phosphorus (P) by Atlantic salmon (Salmo salar). Triplicate groups of salmon parr, initial weight 15 ± 0.5±g , were fed, diets containing 4, 5, 6, 7, 8, 9, 11 and 13 mg P and 20 KJ of digestible energy (DE) per±g of diet (dry matter basis, DMB) to satiation for 16 weeks. The basal diet containing 4 mg P g-1 (0.15 mg available P per KJ DE) was supplemented with graded levels of calcium phosphate, Ca(H2PO4)2⋅H2O to formulate the eight experimental diets. The fish were reared in fresh water at a temperature of 15 °C on a 12 h photoperiod. Vertebrae ash increased from 316 to 516 mg g-1 fat-free dry matter with an increase in dietary P content. P requirement was estimated by using a four-parameter sigmoidal equation. The data suggests that a diet of 0.28 mg available P per KJ DE is needed for Atlantic salmon. Phosphate and calcium levels in plasma and bone increased, whereas levels of magnesium and liver cholecalciferol decreased, with an increase in dietary P. Phosphate excretion in urine and apparent availability of P were determined in deficient and replete fish. In deficient fish, the urine phosphate concentration was 0.10 mmol L-1 before feeding and 0.25 mmol l-1 after feeding, whereas in replete fish these concentrations were 1.09 and 5.11 mmol l-1, respectively. The increase in urine phosphate concentration was higher in replete fish than in deficient fish, however, the apparent absorption of P was found to be significantly lower in replete fish than in deficient fish. These results suggest that similarly to terrestrial vertebrates, P homeostasis in Atlantic salmon is controlled by absorption in the intestine, conservation in the kidney and storage in the bones.
96 citations
TL;DR: Results suggest that P. schlosseri might be able to maintain a low steady state level of internal ammonia during ammonia loading at a concentration which is lethal to other fishes.
Abstract: The aim of this study was to elucidate if the mudskipper Periophthalmodon schlosseri, in relation to its capability to survive on land, has acquired a greater capacity to detoxify ammonia than more aquatic species. The tolerance of P. schlosseri to environmental ammonia was much higher than that of another mudskipper, Boleophthalmus boddaerti, and those of other fishes. The 24, 48, and 96 h median lethal concentrations (LC50) of unionized ammonia (NH3) for P. schlosseri were 643, 556 and 536 µM, respectively. The corresponding LC50 values for B. boddaerti were 77.1, 64.0, and 60.2 µM. The relatively high tolerance of P. schlosseri to ammonia could be partially due to the presence of high activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH, aminating) in its brain. When P. schlosseri and B. boddaerti were exposed to their sublethal NH3 concentrations of 446 and 36 µM, respectively, both mudskippers detoxified ammonia by converting it to free amino acids (FAA). This led to increases in concentrations of total FAA (TFAA) in the brain, liver and muscle. Increases in TFAA concentrations in the brain were mainly due to increases in glutamine concentrations. The activities of GS and GDH in the brain of both mudskippers increased significantly after they were exposed to their respective sublethal concentrations of NH3. Urea production and excretion were not utilized as a means for environmental ammonia detoxification in these mudskippers. The most intriguing results obtained were the lack of effect on any of the parameters studied when P. schlosseri was exposed to 36 µM of environmental NH3. These results suggest that P. schlosseri might be able to maintain a low steady state level of internal ammonia during ammonia loading at a concentration which is lethal to other fishes.
94 citations
TL;DR: Changes in lipid class composition of tissues of anadromous Arctic charr, Salvelinus alpinus, were studied in relation to seasonal patterns of lipid deposition and lipid mobilisation to assess lipid dynamics associated with maturation.
Abstract: Changes in lipid class composition of tissues of anadromous Arctic charr, Salvelinus alpinus, were studied in relation to seasonal patterns of lipid deposition and lipid mobilisation. Charr of a north Norwegian population were collected in late May when fish were migrating towards the sea, and in mid-July when the fish re-entered fresh water. Some maturing fish captured in mid-July were held in captivity until late September to assess lipid dynamics associated with maturation. The carcass (head, fins, skeleton and skin) accounted for approx. 50% of the total body lipid content when the fish re-entered fresh water from the sea. Triacylglycerols (TAG) comprised 75-80% of the carcass lipid in ascending charr, confirming that the carcass is a major lipid depot. The skeletal muscle also represented a major lipid store: muscle of ascending charr contained 35-40% of the body lipids, with TAG being dominant (approx. 75% of muscle lipid). The gut (gastrointestinal tract and visceral lipid) and liver of ascending charr each held only 4-5%; of the body lipid, TAG being the dominant lipid class in both of these depots (Gut TAG: 60-65%; Liver TAG: 50-55%). Body lipid decreased 30-40% during maturation: lipids were depleted from all depots, but mobilisation of from the carcass and muscle was quantitatively the most important. In mature females, the ovaries held almost 25% of the body lipid, with the proportion of TAG exceeding that of polar lipids (PL)(TAG: 62%; PL 12.4%). In the mature males, the testes accounted for less than 3% of the total lipids. TAG tended to dominate the testis lipids (TAG: 29.5%), but there were also quite high proportions of free fatty acids, cholesterol and polar lipids (FFA: 23.5%; C: 15%; PL 9.7%). Females lost approx. 80% of their body lipid during spawning and overwintering, the majority of this being TAG. Males also lost large amounts of TAG during the winter, but in contrast to the females lipid depletion amounted to only 50-55% of that present at the time of ascent into fresh water.
93 citations
TL;DR: In fish fed n-3 HUFA deficient diet, fatty acid composition of TNL of female gonads and eggs reflected the diet more than liver, reflecting the influence of fatty acid levels in the broodstock diets.
Abstract: A feeding experiment was conducted on gilthead seabream (Sparus aurata) broodstock to investigate the incidence of n-3 highly unsaturated fatty acids (n-3 HUFA) dietary deficiencies on the lipid composition of female liver, gonads and eggs, in relation to spawning quality. Broodstock were fed a control (C) diet or a n-3 HUFA deficient (D) but linolenic acid rich diet. After 20 weeks of feeding, the results showed that levels of total neutral (TNL) and total polar (TPL) lipids of female gonads and eggs were independent of diet. However the fatty acid composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) of female liver, gonads and eggs in the two groups of fish showed marked differences, reflecting the influence of fatty acid levels in the broodstock diets. This influence was even higher in TNL than in the phospholipid classes examined. In fish fed n-3 HUFA deficient diet, fatty acid composition of TNL of female gonads and eggs reflected the diet more than liver. A higher egg production in broodstock fed C diet (1.8% n-3 HUFA in diet) was extended to spawning quality such as percentages of fertilised and hatched eggs.
92 citations
TL;DR: Sperm motility and seminal plasma pH were increased by GnRHa treatment, and GnR Ha treatment did not have a negative effect on sperm fertilizing ability, percentage hatch or larval morphology.
Abstract: Compared to control fish, gonadotropin releasing hormone-analogue (GnRHa) treatment delivered either by microspheres or cholesterol pellets successfully increased sperm production (cells kg−1) and milt volume (ml kg−1) in mature yellowtail flounder Pleuronectes ferrugineus during the spawning season. Spermatocrit decreased in both treated and control groups between 12 and 29 days post-implantation, indicating a seasonal decrease in sperm concentration, rather than an effect of the GnRHa treatments. Plasma levels of testosterone, 11-ketotestoterone and 17α,20βdihydroxy-4-pregnen-3-one (17α20βP) showed no clear pattern either across treatments or over days, however this does not exclude the possiblity that GnRHa had its effect on milt volumes via the stimulation of steroid production since the sampling protocol did not allow for the rapid clearance of steroids from the plasma. GnRHa treatment did not have a negative effect on sperm fertilizing ability, percentage hatch or larval morphology. Sperm motility and seminal plasma pH were increased by GnRHa treatment.
TL;DR: It is suggested that canola oil may comprise as much as 47% of the lipid in high-energy grower diets for Atlantic salmon without compromising performance.
Abstract: The effects of various dietary blends of menhaden oil (MO) with canola oil (CO) on the growth performance, whole body proximate composition, flesh quality (muscle proximate and lipid composition) and thyroidal status of immature Atlantic salmon in sea water were studied.
TL;DR: Evidence is provided that estrogen exposure can have delayed action in a teleost in a manner similar to the effects described for mammalian species, and that chronic exposure to E2 past the critical sensitive period may not affect the sex ratio, but could result in alterations in the male reproductive organs.
Abstract: This study investigated the effects of estrogens on sexual differentiation in sea bass (Dicentrarchus labrax L.), a gonochoristic marine teleost that under culture conditions has a histologically sexual undifferentiated period that covers most of the first year of life, after which most individuals develop as males. Sea bass that had no noticeable histological sign of sex differentiation were fed estrogens at two doses (5 or 10 mg kg-1 food) and for different periods ranging from 48 to 426 days post fertilization (DPF). Exposure to the synthetic estrogen 17α-ethynylestradiol (EE2) at 10 mg kg-1 food from 60 to 260 DPF, including the sensitive period to equivalent doses of synthetic androgens previously determined for this species (126-226 DPF), significantly (p < 0.05) more than doubled the number of juvenile females to 80%, compared to the control value of 33%, and completely suppressed gonadal development in the remaining 20% of the population. This suggests that the period during which sea bass gonads exhibit high sensitivity to androgens is also very sensitive to estrogens. A comparable exposure to the natural estrogen estradiol-17β (E2) resulted in 13% of the fish having suppressed gonadal development, but induced 57% of the fish to develop gonads with germinal tissue of both sexes, suggesting a pivotal role for E2 during this sensitive period. Earlier exposure to EE2 at 10 mg kg-1 food from 48-88 DPF, significantly (p < 0.05) increased the number of females to 62% from 36% in the control group, allowing for the normal testicular development in the remaining fish. In contrast, a later chronic exposure (226-426 DPF) to E2, at either 5 or 10 mg kg-1 food, starting when the gonads showed no sign of sexual differentiation but past the critical sensitive period, had no effect on the resulting overall sex ratios, indicating that after this period responsiveness of the gonads to estrogens decreases as gonadal sexual differentiation progresses. However, the consequences of this apparently innocuous exposure were later manifested in adults, exemplified by a significant dose-dependent reduction in the number of mature males at 626 DPF, coinciding with the second reproductive season, the time when males normally reach sexual maturation in cultured sea bass. This suggests that chronic exposure to E2 past the critical sensitive period may not affect the sex ratio, but could result in alterations in the male reproductive organs. This was later verified by histological analysis which revealed a significant (p < 0.05) dose-dependent reduction of the surface of the testicular lobules in the remaining males that did not mature. Together, these experiments illustrate both readily observable and subtle effects of estrogens on sex proportions, gonadal morphology and maturation rates, providing evidence that estrogen exposure can have delayed action in a teleost in a manner similar to the effects described for mammalian species. The possible existence of effects of this latter type in adult fish could be considered when evaluating the consequences of deliberate or accidental exposure to estrogens or putative estrogenic chemicals, particularly if such exposure had taken place during sex differentiation.
TL;DR: The results obtained with plasma of carp, trout and man suggest that HDL acts as an alternative carrier for the transport of free fatty acids in the blood when albumin concentrations are low or absent.
Abstract: It was investigated whether an albumin-like protein, active in the transport of free fatty acids, is present in the blood of the common carp, Cyprinus carpio. In contrast with the brown trout Salmo trutta, no free fatty acid-binding protein could be found with a molecular mass and isoelectric point similar to human serum albumin. On the other hand, free fatty acids bound in this fish species to the apolipoproteins of high density lipoprotein (HDL), namely apolipoprotein A-I and apolipoprotein A-II. In addition to the binding of free fatty acids, carp HDL was also capable of interacting with the lipophilic human serum albumin binding dye, Cibracon Blue. The results obtained with plasma of carp, trout and man suggest that HDL acts as an alternative carrier for the transport of free fatty acids in the blood when albumin concentrations are low or absent.
TL;DR: It is concluded that the deiodinating enzymes in teleosts are more similar to mammalian deiodinases than is generally accepted.
Abstract: The presence of outer ring deiodinating (ORD) and inner ring deiodinating (IRD) activities was investigated in different tissues of Oreochromis niloticus (Nile tilapia), Clarias gariepinus (African catfish), Oncorhynchus mykiss (rainbow trout) and halmus maximus (turbot). High-Km rT3 ORD is present in the kidney of most of the fishes studied, except in catfish. In turbot, besides the kidney, rT3 ORD is also present in liver, heart and ovary. Low-Km T4 ORD is found in the liver and low-Km T3 IR the brain of all the fishes studied. In addition, low levels of low-Km T3 IRD were demonstrated in gill and skin of Nile tilapia, liver of rainbow trout and gill and kidney of turbot. For the different teleosts, the biochemical properties of the different rT3-deiodinating enzymes mentioned, T4 ORD in liver and T3 IRD in brain and tilapia gill were compared to those of the deiodinases formerly characterized in Oreochromis aureus (blue tilapia). In general, the different deiodinases demonstrate analogous sensitivities to iodothyronines and inhibitors, although minor differences occur. The various deiodinating enzymes all depend on addition of dithiothreitol and demonstrate maximal activity pH between 6.5 and 7. The optimal incubation temperature of rT3 ORD and T4 ORD in tilapia and catfish is 37 °C, in trout and turbot it varies, depending on the tissue, between 25 ° and 37 °C. For the different T3 IRD activities the optimal temperature is 37 °C in warmwater as well as in coldwater species. The apparent Km values for rT3 ORD lay in the μM range, for T4 ORD and T3 IRD they lay in the nM range. Vmax values are usually higher in tilapia as compared to the other teleosts studied. Based on the similarities in susceptibility to inhibition by different iodothyronines and inhibitors and the agreement of the apparent Km values, we conclude that the deiodinating enzymes in teleosts are more similar to mammalian deiodinases than is generally accepted.
TL;DR: Results of immunoblotting and RT-PCR indicate that the salinity-dependent stimulation of mRNA of gill Na+-K+-ATPase α subunit is associated with corresponding stimulation at the protein level, providing direct evidence of enhanced transcription and translation of Na-K-ATpase α-subunit gene upon salinity challenge.
Abstract: Using RT-PCR, partial cDNA of Na+-K+-ATPase α subunit of tilapia (Oreochromis mossambicus) was cloned and sequenced. Clone TG3, with 1685 bp encoding a protein of 565 amino acids, showed higher than 85% identity in deduced amino acid sequence with previously published animal Na+-K+-ATPase α-1 subunit genes. Northern blot showed that TG3 is expressed in gills, kidneys and other organs in tilapia. The amount of mRNA in gill tissue increased with the level of environmental salinity. A fragment of TG3 was constructed into a pQE30 expression vector, and the expressed fusion protein was used to raise the antibody, Ab-TG3, in rabbit. Ab-TG3 was found not only to immuno-react with a major protein of approximately 100 kDa in size in gills, kidneys, heart, and brain of tilapia, but also to recognize a similar protein in gills of mudskipper (Periophthalmus cantonesis) and the kidneys, heart and brain of rat. Results of immunoblotting indicate that the amount of Na+-K+-ATPase α submit in gills of seawater-adapted tilapia was significantly higher than that in freshwater-adapted ones. Our results indicate that the salinity-dependent stimulation of mRNA of gill Na+-K+-ATPase α subunit is associated with corresponding stimulation at the protein level. This provides direct evidence of enhanced transcription and translation of Na+-K+-ATPase α-subunit gene upon salinity challenge.
TL;DR: Results suggest that GH-stimulated release of ovarian IGF-I may have an even more direct role than DHP on the reinitiation of oocyte maturation.
Abstract: Recent evidence has indicated the presence of IGF-I and IGF-I receptors in mammalian and teleost ovarian follicles. Since growth hormone (GH), which can be secreted from the pituitary concomitant with a gonadotropin as a response to gonadotropin-releasing hormone, generally acts to release IGF-I from tissues including the ovary, the effect of IGF-I itself on ovarian steroidogenesis and oocyte maturation was investigated in the model teleost, Fundulus heteroclitus. IGF-I was found to be without effect on ovarian follicle steroidogenesis, but initiated oocyte maturation in a dose-dependent manner even more rapidly and effectively than 17α,20β-dihydroxy-4-pregnene-3-one (DHP), the naturally occurring maturation-inducing steroid. IGF-II also induced oocyte maturation in a dose-dependent manner. IGF-I induction of oocyte maturation occurred in the absence of DHP production by the granulosa cells (which is normally stimulated by gonadotropin), and could be inhibited by cycloheximide but not actinomycin D, thus implicating the role of protein synthesis. These results suggest that GH-stimulated release of ovarian IGF-I may have an even more direct role than DHP on the reinitiation of oocyte maturation.
TL;DR: Higher temperatures led to increased absorption and depletion rates of AA, and also to a higher retention efficiency of yolk nutrients, but changes in temperature did not induce preferential absorption or depletion of individualAA, and caused only small variations in the AA profile.
Abstract: The present study investigated the qualitative amino acid (AA) requirements of larval African catfish Clarias gariepinus. Yolk-sac larval AA profiles were measured at different temperatures and also in animals reared at 28 °C fed Artemia nauplii or an experimental dry diet. The AA profile of C. gariepinus larvae changed during ontogeny, especially before the start of exogenous feeding. The AA profiles of the food items (yolk, Artemia and the dry diet) differed considerably from that of the larvae. No selective absorption of yolk AA was detected. Higher temperatures led to increased absorption and depletion rates of AA, and also to a higher retention efficiency of yolk nutrients. However, changes in temperature did not induce preferential absorption or depletion of individual AA, and caused only small variations in the AA profile. Depletion rates of individual AAs varied, possibly due to differences between larval and yolk AA profiles, and also to changes in the larval AA profile during ontogeny. There was little regulation of catabolism of individual AA in yolk-sac and starved larvae, and no sparing of essential AA.
TL;DR: It is suggested that S. pavo, or its marine ancestor, has euryhaline capabilities that enabled it to invade freshwater habitats, and S. fluviatilis, as the evolutionary result of this invasion, is thus better adapted to freshwater environment, but did not lose its ability to live in seawater.
Abstract: This study compares osmoregulatory capabilities of two closely related blennies inhabiting different habitats: Salaria pavo which inhabits marine rocky coasts in the Mediterranean and the eastern coasts of the Atlantic Ocean, and Salaria fluviatilis which inhabits freshwater habitats around the Mediterranean, both in rivers connected to the sea and in lakes that for a long time have been separated from the sea. Fishes for this study were collected in Lake Kinneret (Sea of Galilee) (S. fluviatilis) and Habonim beach, Israel, East Mediterranean coast (S. pavo). Both species tolerated salinities of 0, 40 and 100% seawater (0, 14.4 and 36 ppt sea salt respectively). Acclimation for a period of three months to freshwater (S. pavo) and seawater (S. fluviatilis) did not affect survival rates. After acclimation, total body water content of S. fluviatilis remained unaffected by experimental salinities but increased in S. pavo as salinity decreased. The hematocrit of both species increased as salinity increased. Plasma osmolality and Na+ concentrations were unaffected by experimental acclimation salinities in S. fluviatilis, but significantly decreased in S. pavo as salinity decreased. The results indicate that S. fluviatilis is able to osmoregulate both in fresh and seawater. S. pavo, living in seawater, while able to tolerate freshwater environment, fails to maintain constant extracellular fluid concentration. It is suggested that S. pavo, or its marine ancestor, has euryhaline capabilities that enabled it to invade freshwater habitats. S. fluviatilis, as the evolutionary result of this invasion, is thus better adapted to freshwater environment, but did not lose its ability to live in seawater.
TL;DR: Levels of trimethylamine oxide (TMAO) and urea in various tissues of several teleost fishes of McMurdo Sound, Antarctica were determined and suggest that a dietary arginine/arginase system is an important source of Urea in these species.
Abstract: Levels of trimethylamine oxide (TMAO) and urea in various tissues of several teleost fishes of McMurdo Sound, Antarctica were determined. TMAO levels in muscle tended to be high, with levels in several species exceeding 140 mM kg-1 wet weight. The high levels appear to be necessary to osmotically balance high levels of sodium and chloride in the blood of these species. In two species (Dissostichus mawsoni and Gymnodraco acuticeps), significant levels of TMAO (> 80 mM l-1) were also found in the blood, while virtually no TMAO was found in the blood of a related, temperate water species. In other Antarctic species, serum TMAO levels varied from moderate to low levels. Urea levels in several species were in the range 15–25 mM l-1, which is higher than those in temperate water fishes. The high TMAO and urea levels make important contributions to the fishes' high osmolarities, and thus help to lower freezing points. These data are consistent with previous data obtained from some northern fishes. Fishes with high serum TMAO levels had liver TMAase activity whereas those with no serum TMAO did not. Activity levels of uricolytic enzymes in D. mawsoni and G. acuticeps were not noticeably different from those of temperate water fishes. These species showed moderate to high activities of three ornithine urea cycle enzymes (CPS, OCT and arginase) but low activity of the argininosuccinate synthetase/argininosuccinyl lyase system. These data suggest that a dietary arginine/arginase system is an important source of urea in these species.
TL;DR: The results suggest that the change in hepatic D2 activity is one of the main factors responsible for the changes in plasma T3 observed during starvation and refeeding in tilapia, and supports the hypothesis that, in contrast to mammals and birds, liver D2 is the primary source of plasma T2 in fish.
Abstract: Fasting and refeeding have considerable effects on thyroid hormone metabolism. In tilapia (Oreochromis niloticus), fasting results in lower plasma T3 and T4 concentrations when compared to the ad libitum fed animals. This is accompanied by a decrease in hepatic type II (D2) and in brain and gill type III (D3) activity. No changes in kidney type I (D1) activity are observed. Refeeding results in a rapid restoration of plasma T4 values but not of plasma T3. Plasma T3 remains low for two days of refeeding before increasing to normal levels. Liver D2 and gill D3 also do not increase until two days after refeeding. Brain D3, on the other hand, rises immediately upon refeeding. These results suggest that the change in hepatic D2 activity is one of the main factors responsible for the changes in plasma T3 observed during starvation and refeeding in tilapia. This finding supports the hypothesis that, in contrast to mammals and birds, liver D2 is the primary source of plasma T3 in fish. Although the deiodinases important for the gross regulation of plasma T3 during fasting/refeeding differ (mammals: D1 and D3, birds: D3, fish: D2), they all occur in the liver, suggesting that the organ itself may play a crucial role. In addition, the changes in brain and gill D3 suggest that these enzymes constitute a fine tuning mechanism for regulation of T3 availability at the cellular or plasma levels, respectively.
TL;DR: Genetic variation in trypsin isozyme pattern is a primary factor affecting food conversion efficiency and growth under different rearing temperatures.
Abstract: Hatching and start-feeding temperatures affected the expression of different trypsin isozymes in the pyloric caeca of Atlantic salmon. Hatching temperature of 10 °C induced the expression of the common isozyme TRP-2*100, and of 6 °C induced the variant TRP-2*92 (p$<$0.01). In contrast, start-feeding temperature of 12 °C significantly (p$<$0.0001) influenced the expression of the variant TRP-2*92, compared to 6 °C. The frequencies between different trypsin isozyme patterns were not changed at later stages under varied rearing temperatures.
TL;DR: It is shown that food deprivation can have an important influence on the storage of energy metabolites for anaerobic energy production, particularly in small fish at warm temperatures, and the concentrations of white muscle PCr and ATP were not greatly affected by food deprivation under any of the experimental conditions.
Abstract: The relationship between body size and the depletion of white muscle metabolites (e.g., PCr, ATP, glucose and glycogen) was examined in two sizes (30 or 700 g) of rainbow trout deprived of food for one, four or seven days at either 5 or 15 °C. Following 7 days of food deprivation at 15 °C, the levels of muscle glycogen decreased by approximately 50% in small fish relative to control values (i.e., day 1). In comparison, small fish acclimated to cold temperatures did not exhibit a significant reduction of muscle glycogen over the seven day fasting regime. In contrast to small fish, the levels of white muscle glycogen in large fish remained unchanged after food deprivation, regardless of acclimation temperature. A seven day deprivation of food also resulted in a 50% depletion of white muscle glucose concentrations in small and large fish acclimated to warm temperatures, but there were no significant changes in this variable in fish acclimated to cold temperatures. In contrast to the negative effects of food deprivation on white muscle glycogen and glucose levels, the concentrations of white muscle PCr and ATP were not greatly affected by food deprivation under any of the experimental conditions. Taken together, these results clearly show that food deprivation can have an important influence on the storage of energy metabolites for anaerobic energy production, particularly in small fish at warm temperatures. In the future, it may be very important to consider the physiological effects of short-term food deprivation when interpreting results from studies in which fish have been fasted prior to treatments such as exercise.
TL;DR: These experiments suggest that changes in swimming speed and mouth gape are important for respiratory regulation in ram ventilating sharks.
Abstract: We examined the effect of hypoxia on the swimming speed, respiration rate (oxygen uptake), gape and ventilation volume of the bonnethead shark, Sphyrna tiburo. We used a sonic flowmeter developed for this study to examine swimming speed changes of sharks held in artificial lagoons during diurnal dissolved oxygen changes. Sharks were observed to swim at about 34 cm s-1 during the day but increased to about 40 cm s-1 at night when dissolved oxygen levels fell to < 3 mg l-1. Using a closed system respirometer we examined changes in swimming speed, respiration rate and gape at four dissolved oxygen levels. Swimming speeds averaged 24 to 25 cm s-1 under normoxic conditions but increased to 38 to 40 cm s-1 during hypoxia. Similarly, respiration rate increased with increasing speed and decreasing dissolved oxygen. Gape averaged about 1.0 cm under normoxic conditions and increased to a maximum of about 3.5 cm during hypoxia. Using assumed oxygen extraction efficiencies of 25, 50 and 75% and observed respiration rates, we estimated that ventilation volumes of about 25 to 470 l h-1, depending upon oxygen concentration, would be necessary for gill ventilation. These experiments suggest that changes in swimming speed and mouth gape are important for respiratory regulation in ram ventilating sharks.
TL;DR: Coated lysine proved to be asignificantly better way of supplementing dietary protein, as shown by feed-conversion indices at 18 and 25 °C, andSupplementation with coated lYSine, but not with free lysines, significantlyincreased the protein-synthesis rate (KS) at 18 or25 °C in comparison to lysin deficiency, although not to control values.
Abstract: The effect of protein quality and of supplementati on of corn-gluten protein with lysine on the growth, feed conversion and protein turnover rates in white muscle was investigated in carp (Cyprinus carpio) acclimated to either 18 or 25 °C. Fish fed the lysine-deficient diet showed a significantly lower food intake, weight gain and feed-conversion efficiency than animals fed the lysine-sufficient diets, regardless of environmental temperature. Coated lysine, compared with free lysine, proved to be a significantly better way of supplementing dietary protein, as shown by feed-conversi on indices at 18 and 25 °C. White-muscle protein, RNA and DNA contents were not altered by dietary treatment or water temperature. Supplementation with coated lysine, but not with free lysine, significantly increased the proteinsynthesis rate (K S ) at 18 or 25 °C in comparison to lysine deficiency, although not to control values . The efficiency of protein synthesis (K RNA) and retention (PRE) obtained for fish fed the coated-lysine diet, at 18 °C, reached control values. At 25 °C PRE and protein accumulation rate (K G) showed the following significant differences: lysine-deficient diet < free-lysine supplemented diet < coated-lysine supplemented diet < control diet. Significant correlations were observed for Ks in relation with K D , K RNA or protein-related growth, at both temperatures.
TL;DR: It is concluded that fluorescence-based assays are applicable to the study of lipid digestion in fish of different size and variations in lipolytic activities with gut segment and with size of fish were examined.
Abstract: To study the potential of fluorescence based assays in the study of lipid digestion in fish, acyl esters of 4-methylumbelliferone and 1-acyl-2-[6 (7 nitro-1,3 benzoxadiazol-4-yl)amino]caproyl labeled phosphatidylcholine compounds (NBD-PC) were used as substrates for the assay of neutral lipase and phospholipase, respectively, in the gut contents of turbot. 4-Methylumbelliferyl hepatanoate (4-MUH) was hydrolysed at a higher rate than the butyrate or oleate esters whilst the hexanoic (C6) ester of NBD-PC was a more convenient substrate for the phospholipase assay than the dodecanoic (C12) ester. Neutral lipase activity was almost 10% higher when 50 mm potassium phosphate buffer pH 7.8 was used instead of 0.01 m citrate/sodium phosphate buffer pH 7.2. Both assays were very sensitive: neutral lipase and phospholipase activities were detectable at a minimum protein concentration in the digesta of 0.04 and 1.25 mg/ml, respectively. When the variations in lipolytic activities with gut segment and with size of fish were examined neutral lipase activity was always found to be higher in the hindgut and rectum segments than in the foregut. Although phospholipase activity was also found to be highest in the hindgut of the largest fish examined (av. wt. 182.3g), in fish of average weight 8g fish the activity was similar in all three segments. In the digesta from the whole gut of smaller fish (av. wt. 0.2, 0.6 and 1.43g) neutral lipase and phospholipase activities increased with increasing body mass when expressed as per ml of digesta. It is concluded that fluorescence-based assays are applicable to the study of lipid digestion in fish of different size.
TL;DR: It is concluded that the different environmental conditions, experienced by wild and farmed fish, have significantly influenced the biochemical composition of their lateral muscle.
Abstract: Red and white muscle from specimens of wild and farmed gilthead sea bream (Sparus aurata) were analyzed for histochemical ATPase activity, total protein content, fatty acids, trace element concentrations and myosin isoforms. The fibre type composition of muscle samples was confirmed histochemically by the ATPase reaction, which did not show any differences between the two groups of animals. Myosin ATPase activities, myosin and protein yields were significantly higher in white muscle than in the red muscle and for the red muscle the latter two parameters were higher in wild fish. Fatty acid profiles revealed differences between the two groups of animals, probably because of the fatty acid composition of the diets. Zinc, copper and iron concentrations were higher in red muscle than in white muscle; muscles from wild fish were significantly richer in trace elements. No separation of fast and slow heavy chains of myosin could be obtained on SDS-gel electrophoresis, but two dimensional electrophoresis revealed the presence of three light chains in white muscle (LC1F, LC2F, LC3F), and two main types in red muscle (LC1S, LC2S). Small, variable percentages of LC3F were found in the red muscle samples, especially in the wild fish. It is concluded that the different environmental conditions, experienced by wild and farmed fish, have significantly influenced the biochemical composition of their lateral muscle.
TL;DR: The results support the idea that dietary PC plays a role in the intestinal absorption of neutral lipid fatty acids, and might, at least partially, explain the superiority of PC for enhancing growth.
Abstract: A 28-day feeding trial was conducted for comparing the effect of different dietary phospholipid (PL) classes on the growth of post-larval turbot and on the incorporation of dietary neutral lipid fatty acids into their body lipids. Prior to the experiment the turbot were weaned for one week on a PL-free diet. The nine experimental diets were isolipidic and contained an equal amount of highly unsaturated fatty acids in the form of ethyl esters. They differed by their PL content (0, 1 or 2%) and by the PL class composition of the added soybean PL fractions.
TL;DR: Different water and ion regulatory mechanisms are operating in the tilapia embryos and larvae in FW and those in SW to convey their strong euryhalinity.
Abstract: Euryhaline tilapia (Oreochromis mossambicus) can breed either in fresh water (FW) or in seawater, and the developing embryos and larvae withstand direct transfer from FW to SW or vice versa, before the development of osmoregulatory organs. In the study, developmental changes in drinking rate and ion and water permeability were examined after transfer of the embryos from FW to SW. Drinking was measured by accumulation of fluorescent beads in the intestine and also by 14C-dextran accumulation he whole body. The drinking rate increased steadily from 2 to 10 days after hatching, and the larvae in SW consistently imbibed more water than those in FW. The diffusional water permeability remained low during embryonic stages but increased markedly after hatching in both FW and SW; the water permeability was consistently less in SW-adapted embryos and larvae than those in FW. In contrast, the turnover rates of chloride ion in SW were 50 to 100 times greater than those in FW, and increased markedly after hatching. The drinking rate as well as ion and water permeability of the tilapia embryos and larvae in FW and SW were comparable with those reported for stenohaline species. These results clearly indicate that different water and ion regulatory mechanisms are operating in the tilapia embryos and larvae in FW and those in SW to convey their strong euryhalinity.
TL;DR: The results suggest that DHA can be synthesised in fish brain and eye in vivo in vivo, in both species, especially in the brain and eyes.
Abstract: Accumulation of docosahexaenoic acid (DHA; 22:6n-3) in brain and eyes during development has been demonstrated in fish but it is not clear whether liver or neural tissues themselves are of greater importance in the biosynthesis of DHA from dietary 18:3n-3. In the present study, we investigated the in vivo metabolism of intraperitoneally injected [1-14C]18:3n-3 in liver, brains and eyes of young juvenile fish. Metabolism was followed over a 48h time-course in order to obtain dynamic information that could aid the elucidation of the roles of the different tissues in the biosynthesis and provision of DHA from dietary 18:3n-3. The study was performed in both a freshwater fish, rainbow trout Oncorhynchus mykiss L and a marine fish, gilthead sea bream Sparus aurata L to determine the effect that low or limitingΔ5-desaturase activity may have in this process. As expected, the results showed that although the sea bream incorporated more 18:3n-3 into its lipids, metabolism of the incorporated fatty acid by de saturation and elongation was generally greater in the trout. In liver, the percentages of radioactivity recovered in tetraene and pentaene products were greater in trout than in sea bream although there was no difference in hexaenes. In contrast, the re covery of radioactivity in DHA was significantly greater in brain in trout compared to sea bream. In both species, the percentage of radioactivity recovered in desaturated/elongated products was much lower in liver than in brains and eyes, but that percentage increased over the 48h time-course. In trout though, the highest percentages of desaturated products in brain and eye were observed after 12 and 24h, respectively. However in sea bream the highest percentages of desaturated products in the neural tissues were observed after 24-48h. Radioactivity was recovered in 24:5n-3 and 24:6n-3, intermediates in the Δ4-independent ("Sprecher shunt") pathway for the synthesis of DHA, in both species, especially in the brain and eyes. Overall, although the results cannot eliminate a role for liver in the biosynthesis and provision of DHA for developing neural tissues in fish, they suggest that DHA can be synthesised in fish brain and eye in vivo.