Dorsal White Muscle Research Articles

Spatial and seasonal variation in δ15N and δ13C values in a mesopredator shark, Squalus suckleyi, revealed through multitissue analyses

We used variance decomposition to explore the importance of body size, sex, location, and sampling period as predictors of intrapopulation variation in δ15N and δ13C values in spiny dogfish Squalus suckleyi from the Puget Sound–Strait of Georgia basin. Isotopes in two tissues with long (dorsal white muscle) and short (liver) isotopic turnover rates (~1 year and ~3–4 months, respectively) were sampled to evaluate whether the relative importance of each variable differed depending on the time span over which diet information was integrated. Significant spatial variation was observed in both muscle and liver isotopic composition, whereby location uniquely explained 25 and 17 % of the total variance, respectively. The remaining variables explained considerably less variation in both tissue types. Furthermore, evidence of seasonal isotopic shifts in δ15N and δ13C values was apparent, but differed widely in direction and magnitude among groups. These findings suggest that members of spiny dogfish schools may share a common feeding history, possibly by spending extended time periods (weeks to months) foraging in a spatially fixed region. Another explanation is that individuals may move and feed in aggregations that exist for extended periods. These complex group-level patterns suggest that even for large-bodied, motile predators such as sharks, population-level diet estimates derived from averaging isotope ratios of individuals collected from only a few locations may poorly reflect the true population mean.

Fish fins as non‐lethal surrogates for muscle tissues in freshwater food web studies using stable isotopes

Dorsal white muscle is the standard tissue analysed in fish trophic studies using stable isotope analyses. However, sampling white muscle often implies the sacrifice of fish. Thus, we examined whether the non-lethal sampling of fin tissue can substitute muscle sampling in food web studies. Analysing muscle and fin δ(15)N and δ(13)C values of 466 European freshwater fish (14 species) with an elemental analyser coupled with an isotope ratio mass spectrometer, we compared the isotope values of the two tissues. Correlations between fin and muscle isotope ratios were examined for all fish together and specifically for 12 species. We further proposed four methods of assessing muscle from fin isotope ratios and estimated the errors made using these muscle surrogates. Despite significant differences between isotope values of the two tissues, fin and muscle isotopic signals are strongly correlated. Muscle values, estimated with raw fin isotope ratios (1st method), induce an error of ca. 1‰ for both isotopes. In comparison, specific (2nd method) or general (3rd method) correlations provide meaningful corrections of fin isotope ratios (errors <0.6‰). On the other hand, relationships, established for Australian tropical fish, only give poor muscle estimates (errors >0.8‰). There is little chance that a global model can be created. However, the 2nd and 3rd methods of estimating muscle values from fin isotope ratios should provide an acceptable level of error for the studies of European freshwater food web. We thus recommend that future studies use fin tissue as a non-lethal surrogate for muscle.

Lipid correction model of carbon stable isotopes for a cosmopolitan predator, spiny dogfish Squalus acanthias

Three lipid correction models were evaluated for liver and white dorsal muscle from Squalus acanthias. For muscle, all three models performed well, based on the Akaike Information Criterion value corrected for small sample sizes (AIC(c) ), and predicted similar lipid corrections to δ(13) C that were up to 2.8 ‰ higher than those predicted using previously published models based on multispecies data. For liver, which possessed higher bulk C:N values compared to that of white muscle, all three models performed poorly and lipid-corrected δ(13) C values were best approximated by simply adding 5.74 ‰ to bulk δ(13) C values.

Dietary lipid requirement of juvenile hybrid sturgeon, Acipenser baerii♀×A. gueldenstaedtii♂

Summary A 10-week growth trial was conducted to determine the dietary lipid requirement of juvenile hybrid sturgeon (Acipenser baerii♀ × A. gueldenstaedtii ♂) (initial body weight, 66.7 ± 0.11 g). Seven isonitrogenous (crude protein 370 g kg−1) diets were formulated to contain various levels of dietary lipid (40, 65, 90, 115, 140, 165 and 190 g kg−1) and each diet was fed to triplicate groups of thirty fish at 22.3 ± 0.8°C in twenty one 1 m3 concrete tanks. The results showed that specific growth rate (SGR) significantly increased with dietary lipid level up to 115 g kg−1 (P 0.05). Feed intake (FI) was significantly lower at 40 g kg−1 lipid diet (P 0.05). Feed efficiency (FE), protein efficiency ratio (PER), or protein retention efficiency (PRE) showed no significant difference between diets (P > 0.05). Energy retention efficiency (ERE) was lowest in the fish fed diet with 40 g kg−1 lipid (P < 0.05). Fish serum triglyceride (TG), total cholesterol (TC), phospholipid (PL) and low density lipoprotein cholesterol (LDL-C) were positively correlated to dietary lipid level (P < 0.05). The contents of dry matter, lipid, energy in whole body, and the contents of dry matter and lipid in dorsal white muscle showed a steady increase with the increasing dietary lipid level (P < 0.05). Broken-line regression analysis indicated the dietary lipid requirement for juvenile hybrid sturgeon was 111 g kg−1.

Response and recovery of hybrid sturgeon from subchronic oral administration of cyanobacteria

A 90-day growth trial was conducted on hybrid sturgeon (Acipenser baeri ♀ × A. gueldenstaedtii ♂) to investigate the effect of dietary inclusion of cyanobacteria on growth, feed utilization, and fish tissue microcystins (MCs) accumulation and the recovery of fish when they were free of cyanobacteria. Four diets were formualted isonitrogenous and isocaloric to contain different MCs concentrations: the control diet (free of cyanobacteria), low cyanobacteria diet (LCD, 26.60 μg MCs/g diet), medium cyanobacteria diet (MCD, 78.82 μg MCs/g diet), and high cyanobacteria diet (HCD, 201.03 μg MCs/g diet). During the first 47 days, each diet was fed to fish in five replicates and then all fish were fed the control diet during the next 43 days. The results showed that a dose-dependent decrease in feeding rate (FR) and specific growth rate (SGR) were observed in the fish fed with MCD and HCD. MCs contents in fish liver, intestine, and dorsal white muscle increased with dietary MCs and were time dependent (P < 0.05). After the 43-day recovery, there were no significant differences in FR or SGR between the fish previously fed LCD or MCD and the fish fed with the control diet (P > 0.05), while the fish previously fed HCD showed higher FR and SGR than those fed the control diet (P < 0.05). MCs clearance in fish liver and intestine showed time-dependence during the 43-day recovery.

Nonlethal Sampling of Fish Caudal Fins Yields Valuable Stable Isotope Data for Threatened and Endangered Fishes

AbstractFin clipping is gaining momentum for stable isotope analysis in fish as a nonlethal alternative to lethally collecting dorsal white muscle tissue. The main advantage of fin clipping is the elimination of lethal collection, which thus increases the potential for stable isotope research involving threatened or endangered species. To make comparisons across studies using different methods, the degree to which fin clips and dorsal muscle are correlated for both δ15N and δ13C across time and space must be quantified. We evaluated the efficacy of using caudal fin clips by comparing tissues collected across time (2003‐2005), space (21 streams), and body size (fork length, 40‐140 mm) for juvenile Chinook salmon Oncorhynchus tshawytscha and O. mykiss (rainbow trout and steelhead [anadromous rainbow trout]). We also addressed several analytical and sampling issues to assess the potential benefits and limitations of using fin clips for δ15N and δ13C determination. We found that the relationship between fin and muscle tissue was consistent across years and streams. On average, δ15N was lower in fin tissue than in muscle tissue, whereas δ13C was greater in fin tissue. Although the magnitude of the difference between fin and muscle tissue is lower than the thresholds typically used to define trophic level increases, the biological significance of these differences is context dependent. Power analyses indicated that fin and muscle tissue were equal in their ability to detect differences in δ15N and δ13C in juvenile fish and that larger sample sizes are needed to statistically quantify these differences. Finally, the use of fin clips is not a viable option for smaller fish (&lt;50 mm) because the majority of the caudal fin is necessary for analysis. Nonetheless, fin clipping does represent a promising nonlethal sampling technique for quantifying δ15N and δ13C in juvenile salmonids.

Differences between lipid content and composition of different parts of fillets from crossbred farmed carp (Cyprinus carpio)

Common carp (Cyprinus carpio) is, globally, one of the most important farmed fish species. We have analyzed carp from a natural pond-production system in South Bohemia. Ongrowing fish had access to an abundant plankton population which was supplemented with cereals. Fatty acid composition (FA) was investigated in three parts of fillets from four crosses of carp. The FA composition of the leanest part, the dorsal white muscle was similar to that of marine-farmed species; it contained a large proportion of n-3 highly unsaturated FA, the n-3/n-6 ratio was 1.1, and the proportion of phospholipids was high. The abdominal wall is rich in monounsaturated FA, the n-3/n-6 ratio is lower, 0.5, and it is more affected by the cereal feed. We concluded that the lipid composition of all these carp tissues can be improved in terms of healthy FA profile.

Morfologia e crescimento do músculo estriado esquelético no pirarucu &lt;em&gt;Arapaima gigas&lt;/em&gt; Cuvier, 1817 (Teleostei, Arapaimidae)

The aim of this work was to evaluate the morphological and growth characteristics of skeletal muscle tissue in pirarucu (Arapaima gigas) using alevins (50 days old) and juveniles (1 year old). Muscle samples were collected from dorsal, lateral cranial, and lateral caudal regions, and then frozen in liquid nitrogen. Histological frozen sections (10 &micro;m) were stained with HE and Gomori Trichrome for morphological analysis, and NADH-TR to evaluate muscle fiber oxidative metabolism. Morphometric analysis samples were obtained from dorsal and lateral cranial regions, and smallest diameter white fibers were measured. White dorsal muscle was thicker and two muscle fiber compartments were identified in the lateral cranial region: red (superficial) and white (deep) muscle. Hyperplasia muscle growth predominated in alevins and hypertrophy in juveniles.

Effect of triploidy on quality traits of shi drum (Umbrina cirrosa L.) until the second rearing year

Carcass and flesh morphometric, reological and chemical traits of triploid (3n) and diploid (2n) shi drum (Umbrina cirrosa L.) were evaluated through 7 months. Three age groups, 17-, 21- and 24-month-old fish, were investigated. The effects of ploidy were statistically evaluated and the weight of fish was included in the model as a covariate because triploids grew less than diploids. As expected, fish weight was found to be significantly correlated with all the investigated morphometric traits, but showed a negative correlation with some chemical (pH) and colour traits (lightness) of raw fillet. In comparison with controls, triploid shi drums were characterized by different morphological traits that involved a slender body shape. In triploids, a reduction in condition factor, backbone weight, dressing index and an increase in the agility index were also recorded. When the commercial size (i.e. over 300 g) was achieved, triploids exhibited larger coelomatic and fillet (dorsal white muscle) fat deposition than diploids. Among reological traits, colour and texture were affected by ploidy; raw fillet lightness and cooked flesh tenderness were higher among triploids in all the investigated age groups. As fish were fed with a restricted feeding regimen, fillet fat deposition was supposed to be limited. Thus, the effects of ploidy on reological traits may be only partially explained by lipid fillet amount and are supposed to be more related to different fibre muscle architecture.

Essential amino acid supplementation to fish meal-based diets with low protein to energy ratios improves the protein utilization in juvenile rainbow trout Oncorhynchus mykiss

Two 10-week feeding experiments were conducted to evaluate the supplemental effect of essential amino acids (EAA) to fish meal-based diets with low digestible crude protein (DCP) to digestible energy (DE) ratio (DCP / DE) on the growth and protein utilization in juvenile rainbow trout. In each experiment, the control diet having DCP / DE of 24 g/MJ was compared to three lower DCP / DE diets of ratios of 17 and 16 g/MJ in Experiment 1 and 2, respectively. The ingredients containing protein in the control diet were proportionally reduced in the low DCP / DE diets. To the low DCP / DE diets, EAA were: 1) unsupplemented; 2) supplemented to meet the requirements; and 3) supplemented corresponding to 1.2 times the requirements. Each diet was fed to apparent satiation twice a day to juveniles (initial body weight of 21 and 17 g, respectively) at 17 °C. In both experiments, the growth of fish was not affected by the dietary treatments, however, the feed efficiency was significantly improved in fish fed the low DCP / DE diet supplemented with EAA at 1.2 times the requirements. Whole body fat content increased whereas the crude protein content decreased in fish fed the low DCP / DE diets relative to those for the control diet, however, the crude protein content of fish fed the low DCP / DE diet supplemented with EAA at 1.2 times the requirements was significantly higher than fish fed the low DCP / DE diet without the EAA supplementation. Accordingly, percentage nitrogen retention was 50–52% in the group fed diets with the higher levels of supplemental EAA compared to 35–36% in the control diet group. By the supplementation of EAA at 1.2 times the requirements, the concentrations of most of free EAA in plasma, liver, and dorsal white muscle of the low DCP / DE diet group increased to identical levels of fish fed the control diet. Taurine concentration in the plasma and tissues showed an opposite postprandial change to that of ordinal amino acids: the concentration decreased after feeding and the lowest levels were noted at around 15 h after feeding. The results of these experiments indicate that juvenile rainbow trout grow well on 16 g DCP/MJ DE diets based on fish meal, and EAA supplementation to these diets improves the protein utilization and thus reduces nitrogen loading into the environment.

Detection of giant myofibrillar proteins connectin and nebulin in fish meat by electrophoresis in 3-5 gradient sodium dodecyl sulfate polyacrylamide slab gels.

An improved method was investigated for sodium dodecyl sulfate polyacrylamide slab gel electrophoresis (SDS-PAGE) to facilitate the analysis of the giant myofibrillar proteins, connectin and nebulin, in fish meat by using jack mackerel (Trachurus japonicus) as the sample fish. It was established that separation of the alpha-connectin band from the beta-connectin band by SDS-PAGE could be achieved by using 3-5% gradient gels with glycerol to facilitate the formation of a gradient with polymerization at 35 degrees C. SDS-PAGE samples of white dorsal muscle from the jack mackerel were homogenized with a 2% SDS solution containing an inhibitor mixture (1 microg/mL of phenylmethanesulfonyl fluoride, 1 microg/mL of leupeptin, and 1 microg/mL of E-64) and heated at 50 degrees C for 20 min. Heating these samples at 100 degrees C for 2 min resulted in the disintegration of connectin but did not affect nebulin. A purified myofibril sample and a whole muscle sample showed similar changes in the overall rate of degradation of whole connectin and nebulin during the postmortem storage period, but it was clear that beta-connectin was cleaved from alpha-connectin during the preparation of myofibrils at the early stage postmortem. Storage of the SDS-PAGE samples at -85 degrees C was preferable to storage at -18 degrees C for a long period.

Influence of feeding diets with and without fish meal by hand and by self-feeders on feed intake, growth and nutrient utilization of juvenile rainbow trout ( Oncorhynchus mykiss)

Feed intake, growth performance and nutrient utilization by juvenile rainbow trout fed diets with and without fish meal were compared between two feeding regimes: manual feeding and self-feeding. A fish meal-based diet and two non-fish meal diets, fortified with and without essential amino acids (EAA) to simulate the EAA composition of the fish meal diet, were prepared. The two non-fish meal diets were composed mainly of extruded defatted soybean meal (ExSBM), meat and bone meal (MBM) and corn gluten meal (CGM). Each diet was fed to four replicate groups (initial BW; 19.0±2.3 g, 700 g/60 l tank) either by hand to apparent satiation twice daily (0800 and 1730 h) or by self-feeders (feeds were dispensed by fish demands during the light phase) for 60 days at 17 °C under a 14 h light and 10 h dark cycle. Feeding regime did not significantly affect feed intake, weight gain, protein and energy retention, or whole body proximate composition ( P>0.05). Fish fed with the non-fish meal diet with EAA supplementation attained equivalent weight gain and retention of protein as the fish fed with the fish meal diet. However, these parameters for fish fed with the non-fish meal diet without EAA supplementation were significantly inferior ( P<0.05). The whole body fat content of fish fed with this diet was significantly higher than that of fish fed with the other diets. Free EAA levels in the plasma of fish fed with the EAA supplemented non-fish meal diet were similar to those fed with the fish meal diet except for threonine, which was lower in the EAA supplemented non-fish meal diet group. The branched-chain amino acid levels in the plasma of the two non-fish meal diet groups fed by hand increased more sharply and reached higher levels after feeding compared with fish fed with the same diets by self-feeders. The low levels of free threonine, methionine and lysine in the dorsal white muscle of fish fed with the EAA-unsupplemented non-fish meal diet increased in fish fed with the EAA supplemented non-fish meal diet, this increase was especially notable in the manually fed fish. Free non-essential amino acid levels in muscle of fish fed with the non-fish meal diet without EAA were generally the highest among the treatments. The feeding regime affected the levels of serine, glycine and hydroxyproline levels in the muscle (manual feeding<self-feeding). The results of this study indicate that a combination of ExSBM, MBM and CGM, when EAA are supplemented, has the potential to totally replace fish meal in juvenile rainbow trout diets. Feeding diets by self-feeders proved to attain growth and feed performance comparable to those fed by hand. Self-feeding non-fish meal diets affected certain amino acid levels in the plasma and muscle but the effects were not reflected in their growth and protein utilization in this 60-day feeding period.

The effects of dietary retinoic acid on body lipid deposition in juvenile red sea bream ( Pagrus major); a preliminary study

A 6-week feeding trial was conducted to investigate the effects of dietary retinoids, especially retinoic acid, an anti-adipogenic factor in mammals, on lipid deposition in juvenile red sea bream (initial body weight: 8.5 g). The fish were fed either a commercial diet (control: diet 1, crude protein 61.7%, crude fat 13.9%), or diets supplemented with 100 mg retinyl acetate (diet 2), 10 mg all- trans-retinoic acid (diet 3), or 100 mg all- trans-retinoic acid/kg diet (diet 4) for the test period. A low mortality (2.5%) was observed with diets 3 and 4 through the period. Weight gain, daily feed intake, feed efficiency, whole body crude protein, and crude fat content were not affected by the treatments. Visceral adiposomatic index of the fish was highest in fish fed diet 4 as follows: 2.90 in diet 1 fish, 3.46 in diet 2 fish, 3.28 in diet 3 fish, and 4.19 in diet 4. The treatments did not affect hepatosomatic index. Lipid in the dorsal white muscle was lowest and those in the visceral adipose tissue highest in fish fed diet 4. Liver lipid content was not affected by the treatments. Average plasma free fatty acid levels in fish fed diet 4 (60 μEq/l) were lower than those of the other groups (113–148 μEq/l). Plasma triacylglycerol levels in fish fed diet 2 (1845 mg/l) were lower than those of the other groups (2944–3130 mg/l). Subsequently, to confirm that dietary retinoic acid was internally absorbed, plasma retinoic acid levels at 6-h post-feeding were determined by HPLC. These were 4±0 ng/ml in diet 1, 6±0 ng/ml in diet 2, 20±0 ng/ml in diet 3, and 223±34 ng/ml in diet 4. The present results suggest that dietary retinoic acid was directly incorporated into the body, and that retinoic acid up-regulated development of the visceral adipose tissue and down-regulated lipid deposition in the dorsal white muscle.

Sonic/Vocal Motor Pathways in Squirrelfish (Teleostei, Holocentridae)

Similar to many teleost fish, squirrelfish (family Holocentridae) produce vocalizations by the contraction of muscles that lead to vibration of the swimbladder. We used biotinylated compounds to identify the position and extent of vocal motor neurons in comparison to additional motor neuron groups, namely those of red and white dorsal epaxial muscle and opercular muscle that are located adjacent to or near the sonic muscle. The sonic motor nucleus (SMN) was located in the caudal medulla and rostral spinal cord in a ventrolateral position with dendrites extending dorsally in a dense bundle along the lateral edge of the medulla and axons exiting via ventral occipital nerve roots. Transneuronal transport of biocytin identified premotor neurons within the SMN and in the medially adjacent reticular formation that projected to the contralateral SMN and more rostrally to the octavolateralis efferent nucleus and nucleus praeeminentialis, suggesting interactions between vocal and octavolateralis systems as seen in other teleosts. Motor neurons innervating the red and white dorsal muscle formed a loose aggregate in the dorsal motor column, adjacent to the medial longitudinal fasciculus, sending fibers bilaterally throughout the spinal cord with axons exiting via ventral spinal nerve roots. Opercular motor neurons were located within the facial motor nucleus. The anatomical characteristics of the SMN of squirrelfish, a representative member of the order Beryciformes, are similar to those of representative members of the closely related order Scorpaeniformes, but diverge from the SMN of more distantly related orders of paracanthopterygiian and ostariophysan teleosts. These results therefore suggest a possible homology among the SMNs of acanthopterygiian fishes.

The influence of dietary protein and fat levels on tissue free amino acid levels of fingerling rainbow trout ( Oncorhynchus mykiss)

The influence of six semi-purified diets having different nutrient composition on the tissue free amino acid (FAA) levels of fingerling rainbow trout was examined. Four balanced amino acid diets (casein:gelatin=6:1) with combinations of two protein levels (35% (LP) and 50% (HP)) and two fat levels (10% (LF) and 20% (HF)), and two imbalanced high-protein (50%) diets (IMB-HP, casein:gelatin=1:1) with two fat levels (LF and HF), were each fed to duplicate groups (30 fish/group, 10 g/fish) for 6 weeks at 15°C. FAA in plasma, liver, dorsal white muscle and brain at 12 h after the last feeding were compared. Percentage weight gain of the HPHF diet group was the highest, but was not different ( P>0.05) from the others except for the IMB-HPLF diet group ( P<0.05). Levels of individual amino acids in the whole body protein were not markedly different among the treatments. Most of the free essential amino acid (EAA) levels in the tissues of the HP diet fed fish were higher than in those of the LP diet group. The levels of free phenylalanine and tyrosine of the HF group tended to be higher, and those of taurine lower, than the LF group. Most of the free EAA levels of the IMB diet group were lower even than the LP group. Correlations in EAA patterns between a given diet and tissue were high in plasma, but very low in muscle and brain. These findings suggest that not only dietary protein level and amino acid profile, but also dietary fat level affects the levels of certain FAA of rainbow trout tissues.

Phosphorylation state of red and white muscle in tilapia during graded hypoxia: an in vivo (31)P-NMR study.

The aim of this study was to measure the energetic consequences of hypoxia in different types of skeletal muscle within a single tilapia species (n = 5). To that aim, 81.0 MHz (31)P-nuclear magnetic resonance (NMR) spectra were collected, alternately, from three surface coils placed adjacent to the tissues of interest (dorsal white muscle, ventral white muscle, and lateral red muscle) during a graded hypoxia load over 6 h followed by a 5-h recovery period. The fish were contained in a flow cell, enabling us full control of the oxygen content of the bathing medium. The intracellular pH and the concentrations of ATP, phosphocreatine (PCr), and P(i) were determined from the NMR spectra. For normoxia, biochemical differences for [gamma-ATP], [PCr], and [sugar phosphates] (SP) were observed between all three locations, especially between the red and white muscle. During hypoxia stress, loss of phosphorylated compounds (PCr+P(i)+SP) was observed at all locations but was the most severe in red muscle. When the aerobic (respirometry) and anaerobic ((31)P-NMR) ATP production via an energy balance are compared, flexible metabolic depression is demonstrated during anaerobioses. It is concluded that control of the aerobic and anaerobic component of metabolism during metabolic depression is independent of each other.

Desmin Degradation in Postmortem Fish Muscle

ABSTRACTThe degradation of desmin was studied in postmortem white dorsal muscle from sea bass, brown trout, turbot and sardine, stored at 0–4°C. Based on desmin specific antibody tests, results showed that the extent and rate of desmin degradation in postmortem fish muscle varied considerably among species. There was no degradation of desmin during the first 4 days postmortem storage of sea bass and brown trout, whereas 10 to 20% of muscle desmin was degraded during the first 4 days of postmortem storage of turbot. Sardine muscle presented a very complex pattern of desmin degradation products and aggregated desmin fragments detected within the first 24h. Most polypeptides were larger than the nondenatured desmin. Desmin degradation would not be a suitable marker for evaluation of postmortem changes of stored fish.

Role of adipocytes in the muscle tissue of Atlantic salmon ( Salmo salar ) in the uptake, release and retention of water-soluble fraction of crude oil hydrocarbons

The uptake and depuration of the water-sol‐uble fraction (WSF) of hydrocarbons of crude petroleum by Atlantic salmon (Salmosalar) has previously been examined in terms of whole muscle. The hypothesis that the tainting WSF in the muscle was retained primarily by adipocytes has been investigated by the isolation of adipocytes and the subsequent analysis for hydrocarbons in adipocytes. After 96 h exposure of market-sized Atlantic salmon to 0.2 ppm WSF, adipocytes isolated from the belly flap region of the muscle tissue accumulated 14.3 times more WSF (59.4 ppm) than the dorsal white muscle (4.2 ppm), while 54% of the tainting WSF in the dorsal white muscle was found to be stored in associated adipocytes. When returned to clean seawater, WSF accumulated in the dorsal white muscle was released much faster than that in the adipocytes. These results indicated that the loose association of WSF with the nonlipid portion of white muscle, mainly muscle cells and intercellular fluid, is responsible for the rapid discharge of WSF from the dorsal muscle tissue in the early stages of depuration. After 4 d of depuration, the adipocytes became the principal storage site of residual WSF in white muscle and the depuration of WSF from muscle tissue then reflected the release of WSF from adipocytes in the muscle tissue. After 20 d of depuration, 10.7 ppm of tainting WSF in the form of high molecular weight aromatic hydrocarbons (mainly C4-benzenes, naphthalene and alkylated naphthalenes) were still present in adipocytes, while in the dorsal white muscle only a trace of total WSF was detected. Increases in the number of aromatic rings and the alkylations on the rings enhanced the accumulation and retention of individual hydrocarbons in both adipocytes and white muscle. From these studies we conclude that it is the adipocytes in the muscle tissue which control the actual accumulation and release of hydrocarbons in the whole muscle tissue of Atlantic salmon.

養殖マダイの肉質改善に関する研究 ＩＶ 養殖マダイの成長に伴う魚体内各部中脂肪量の変化

To clarify the aspect concerning the accumulation and diminution of fat in various parts accompanying the growth of cultured red sea bream, using fish aged 0, 1, and 2, physique and fat contents in muscle parts, visceral parts, hepatopancreas, dorsal white muscle, and the whole body were measured monthly over a year. According to this survey the following results were confirmed. 1. The monthly changes of fat content except in visceral parts showed a striking contrast between fish aged 0 and 1. The mutual relationships among fat contents of various parts showed a significant and positive correlation in increase and decrease. 2. The changing tendencies of fat contents in various parts depend upon the season. Namely, while fat content in hepatopancreas, muscle parts, and whole body of fish aged 1 showed a rapid increase in autumn, the changes of fat content in visceral parts were very limited and kept a level of around 40g/100g tissue. Dorsal white muscle, too, showed only a little increase after the season. 3. Once superfluous fat has been accumulated in muscle parts it is very difficult to diminish.

Distribution of free L-histidine and its related compounds in marine fishes.

By high-performance liquid chromatography the distribution of L-histidine, carnosine, anserine, and balenine was examined in the white and red muscles of nine species of marine fishes. The L-histidine contents of white muscle were 15.8-92.8μmol/g in dark-fleshed fishes, 0.0734-0.931μmolg in white-fleshed fishes, and 4.06-20.3μmol/g in intermediate fishes. The L-histidien contents fo red muscle were lower than that of white muscle. Balenine as well as 1-and 3-methy ?? -L-histidine was detected only in a trace amount in a few species. In contrast, carnosine and anserine were found in the white and red muscles of almost all species, in which skipjack white muscle showed the highest contents of 2.46-5.57μmol/g (carnosine) and 7.69-21.2μmol/g (anserine). In skipjack tuan, L-histidine, carnosine, and anserine were distributed at somewhat higher levels in dorsal white muscle than in ventral muscle. The level of each compound differed significantly among the anterior, middle, and posterior portions of skipjack red muscle. In skipjack tuna, L-histidine was also detected in other tissues, such as intestine, stomach, pyloric caecum, with the highest level of 20.9μmol/g in pyloric caecum. Carnosine and anserine were also present in these tissues, but in smaller amounts.