Effect of lignite fulvic acid on growth,antioxidant ability,and HSP70 of Pacific white shrimp, <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

This study was conducted to evaluate the effects of fulvic acid (0, 0.3, 0.6, 0.9, and 1.2%) as feed additive on growth, feed utilization, antioxidant ability, and HSP70 in hemolymph and hepatopancreas of juvenile white shrimp Litopenaeus vannamei (average weight 2.5 g) reared under experiment conditions. Shrimp were stocked at a density of 625 shrimps m^?3 for 60 days in net cages submerged in recirculating tanks. At the end of the experiment, specific growth rates and survival rates of shrimp in treatment groups fed with 0.6, 0.9, and 1.2% fulvic acid were higher compared to that of the control group. Shrimp fed 0.6, 0.9, and 1.2% fulvic acid had significantly lower feed conversion rates than those fed control diet. The optimum dietary fulvic acid requirement for juvenile shrimp based on weight gain was 0.897%. Furthermore, superoxide dismutase activity and peroxidase activity increased significantly, while malonaldehyde content decreased in the hemolymph and hepatopancreas of shrimp fed 0.9 and 1.2% dietary fulvic acid. Glutathione content increased obviously in hemolymph of shrimp fed 0.6, 0.9, and 1.2% fulvic acid. In hepatopancreas, glutathione content was significantly higher in shrimp supplemented with 1.2% fulvic acid. HSP70 decreased obviously in hemolymph of shrimp fed 0.9 and 1.2% fulvic acid, while shrimp fed with 0.6 and 0.9% fulvic acid showed lower HSP70 level in hepatopancreas. The results of this study demonstrated that dietary fulvic acid could improve survival rates, growth, feed utilization, antioxidant capability, and stress resistance of juvenile L. vannamei reared under intensive stocking conditions.     

Astaxanthin degradation and lipid oxidation of Pacific white shrimp oil: kinetics study and stability as affected by storage conditions

The kinetics of astaxanthin degradation and lipid oxidation in shrimp oil from hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) as affected by storage temperature were studied. When shrimp oil was incubated at different temperatures (4, 30, 45 and 60 °C) for 16 h, the rate constants (k) of astaxanthin degradation and lipid oxidation in shrimp oil increased with increasing temperatures (p < 0.05). Thus, astaxanthin degradation and lipid oxidation in shrimp oil were augmented at high temperature. When shrimp oils with different storage conditions (illumination, oxygen availability and temperature) were stored for up to 40 days, astaxanthin contents in all samples decreased throughout storage (p < 0.05). All factors were able to enhance astaxanthin degradation during 40 days of storage. With increasing storage time, the progressive formation of primary and secondary oxidation products were found in all samples as evidenced by the increases in both peroxide values (PV) and thiobarbituric acid reactive substances (TBARS) (p < 0.05). Light, air and temperatures therefore had the marked effect on astaxanthin degradation and lipid oxidation in shrimp oils during the extended storage.     

The effects of starvation on fast-start escape and constant acceleration swimming performance in rose bitterling (<Emphasis Type="Italic">Rhodeus ocellatus</Emphasis>) at two acclimation temperatures

To investigate the effects of starvation and acclimation temperature on the escape ability of juvenile rose bitterling (Rhodeus ocellatus), we measured the fast-start escape and constant acceleration swimming performance of fish fasted for 0 (control), 1 and 2 weeks and half-lethal periods (6 or 4 weeks) at two temperatures (15 and 25 °C). Fish acclimated at a high temperature exhibited shorter response latency (R), higher maximum linear velocity (V _max) and longer escape distance during escape movement (D _120ms) than those at the low temperature. Starvation resulted in a significant decrease in V _max and D _120ms at either low or high temperature and a significant increase in R at only the high temperature in the half-lethal period groups (P < 0.05). The relationship between V _max (Y, m s^?1) and starvation time (X, week) was Y ₁₅ = ?0.062X + 1.568 (r = ?0.665, n = 36, P < 0.001) at low temperature and Y ₂₅ = ?0.091X + 1.755 (r = ?0.391, n = 40, P = 0.013) at high temperature. The relationship between U _cat (Y, cm s^?1) and starvation time (X, week) was Y ₁₅ = ?1.649X + 55.418 (r = ?0.398, n = 34, P = 0.020) at low temperature and Y ₂₅ = ?4.917X + 62.916 (r = ?0.793, n = 33, P < 0.001) at high temperature. The slopes of equations showed a significant difference between low and high temperature (F _1,63 = 9.688, P = 0.003), which may be due to the different energy substrate utilization when faced with food deprivation at different temperatures.     

Alternative microalgal diets for cultivation of the fairy shrimp <Emphasis Type="Italic">Branchinella thailandensis</Emphasis> (Branchiopoda: Anostraca)

Fairy shrimp is known as a nutritional food for fish and crustaceans in aquaculture. In most hatcheries, the microalga Chlorella sp. appears to be the most common, suitable, and nutritious food to feed fairy shrimp. In this study, we attempted to determine other alternative algal diets for cultivation of fairy shrimp Branchinella thailandensis. Seven experimental diets including three treatments of dried Spirulina sp. at 0.75 (S1), 1.5 (S2), and 3.0 mg dry weight individual^?1 (S3); three treatments of Chlorococcum humicola at 5 × 10⁵ (Ch1), 1 × 10⁶ (Ch2), and 2 × 10⁶ cells mL^?1 (Ch3); and a control diet (Chlorella vulgaris at 1 × 10⁶ cells mL^?1) were fed to 5-day-old shrimp for 15 days. Evaluation of growth performance, egg production, survival percentage, and nutritional and carotenoid content of the experimental fairy shrimp revealed that Ch3 is the most suitable algal diet. Our results suggest that C. humicola is the best alternative food source for the cultivation of B. thailandensis. In addition, dried Spirulina powder is also a good choice when live algae are not available and can be used as an alternative feed in fairy shrimp cultures.     

Role of cyclooxygenase-mediated metabolites in lipid metabolism and expression of some immune-related genes in juvenile grass carp (<Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>) fed arachidonic acid

Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid (ARA) to prostaglandins, and COX-mediated metabolites play important roles in the regulation of lipid metabolism and immunity in mammals. However, such roles of COX in fish remain largely unknown. In this study, we designed three semi-purified diets, namely ARA-free (control), ARA, and ARA + acetylsalicylic acid (ASA; a COX inhibitor), and used them to feed grass carp (27.65 ± 3.05 g) for 8 weeks. The results showed that dietary ARA significantly increased the amount of ARA in the hepatopancreas, muscle, and kidney (P < 0.05), whereas this increase was reduced by dietary ASA. The hepatopancreatic prostaglandin E₂ content increased in the ARA group, and this increase was inhibited by ASA (P < 0.05). ARA decreased the lipid content in the hepatopancreas, whereas ASA recovered lipid content to a significant level (P < 0.05). ARA significantly decreased the messenger RNA (mRNA) expression levels of fatty acid synthase and stearoyl-CoA desaturase in the hepatopancreas (P < 0.05). However, ASA did not rescue the mRNA expression of these genes (P > 0.05). Interestingly, ARA significantly enhanced the level of peroxisome proliferator-activated receptor α gene expression, and this increase was attenuated by ASA (P < 0.05). Finally, ARA significantly enhanced the mRNA expression of myeloid differentiation factor 88 (MyD88) in the kidney, and ASA attenuated the expression of toll-like receptor 22 and MyD88 (P < 0.05). In conclusion, our findings suggest that COX metabolites play important roles in the inhibition of lipid accumulation in the hepatopancreas of grass carp fed with ARA and that regulation of gene expression promotes lipid catabolism rather than lipogenic activities. Additionally, these eicosanoids might participate in the upregulation of immunity-related genes in the kidney.     

Effects of cold acclimation on the survival,feeding rate,and non-specific immune responses of the freshwater red claw crayfish (<Emphasis Type="Italic">Cherax quadricarinatus</Emphasis>)

The effect of cold acclimation on growth performance, non-specific immune responses, and expression level of HSP21 and CSP gene were studied in red claw crayfish (Cherax quadricarinatus) using a 4-week stress trial. We set a four-temperature gradient, with water temperatures of 25, 20, 15, and 9 °C, respectively. With the gradual decrease of temperature, the survival rate, feeding rate, and hepatopancreas index (HIS) of the red claw crayfish showed a decreasing trend. Decreased total hemocyte count (THC) and hemocyanin concentration were observed when water temperature decreased. The activities of superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in the hepatopancreas and hemolymph all gradually declined with decreasing temperatures and then significantly lowered at 9 °C compared with those at 25 °C. The activity of glutathione peroxidase (GPx) in these two tissues showed in the opposite trend, indicating that they may have different regulation mechanisms. A gradual increase of malondialdehyde (MDA) concentration was detected in the hepatopancreas and hemolymph when the temperature decreased. Low temperature stress also affected the expression of heat shock proteins 21(HSP21) and cold shock domain protein (CSP). These results indicate that cold acclimation may induce oxidative stress on the crayfish and then cause oxidative damage and hemocyte apoptosis, as well as immunosuppression in Cherax quadricarinatus, which may finally affect the growth and survival of Cherax quadricarinatus.     

Effects of potential probiotic <Emphasis Type="Italic">Lactococcus lactis</Emphasis> subsp. <Emphasis Type="Italic">lactis</Emphasis> on digestive enzymatic activities of live feed <Emphasis Type="Italic">Artemia franciscana</Emphasis>

In the present study, cellulase, protease, lipase and amylase activities were performed to investigate the effects of Lactococcus lactis subsp. lactis CF4MRS bioencapsulation of Artemia franciscana. Our results show that cellulase activities (total cellulase—FPase activity, exoglucanase and endoglucanase—CMCase activity) were significantly higher (P < 0.05) in A. franciscana tissue homogenates compared to those in the control group after 8 h of L. lactic bioencapsulation. Notably, an exception case was found in β-D-glucosidase activity, whereby the cellulase activity was not significantly different (P > 0.05) compared to the control group. Administrations of L. lactis at cell concentration of 10⁸ CFU mL^?1 showed considerable improvement of other important enzymatic activities such as amylase, protease and lipase in A. franciscana. The amylase/protease ratio in probiotic-treated A. franciscana was recorded at 0.343, approximately two times higher than those without probiotic administration (0.184). In contrary, amylase/lipase ratio showed half of a reduction (0.330) in L. lactis-administrated A. franciscana compared to the control (0.614). Our study suggests that important digestive enzymes, e.g., cellulase, amylase, protease and lipase, can be enhanced through bioencapsulation of A. franciscana with L. lactis subsp. lactis, which could in turn lead to further stimulation of endogenous enzymes in the fish and shrimp larvae.     

Genetic diversity status of Pacific white shrimp (<Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>) using SSR markers in Iran

Genetic diversity is vital for the maintenance of genetic pool in cultured shrimps. In order to estimate the current status of genetic diversity in Litopenaeus vannamei shrimp in Iran, as an exotic species, a total of 45 individuals from Amiri and Gorgeaj farms in Jask port of Hormozgan province and one hatchery in Gomishan city of Golestan province, were detected using four microsatellite loci. The number of alleles per locus was 5–10, and the mean effective number of alleles (N _e) across populations and loci ranged from 4.834 to 5.148. The overall mean observed heterozygosity (H _o) ranged from 0.450 to 0.479, which was lower than the expected one (0.789–0.794). There was nothing remarkable about any of the allele frequencies across populations or loci. The mean inbreeding coefficient (F _IS) and pairwise genetic differentiation (F _ST) among populations were 41.6 % and 0.133, respectively. The three studied populations departed from Hardy–Weinberg equilibrium (HWE). Analysis of molecular variance revealed 14 % variability among and 86 % within populations. However, considering departing from HWE and the high F _IS and F, the moderate pairwise F _ST values, importance of introducing genetically diverse broodstock and monitoring to control inbreeding is discussed.     

Molecular cloning and characterization of an inhibitor of apoptosis protein in the mud crab <Emphasis Type="Italic">Scylla paramamosain</Emphasis>: its potential anti-apoptosis role under air exposure stress

The mud crab Scylla paramamosain is a widely farmed commercial species in southeast coastal areas of China. The crabs are placed in water-free containers for transportation to inland markets, thus are exposed to dry conditions for more than 72 h after capture and may suffer from air exposure stress, triggering cell apoptosis leading to death. To evaluate whether an inhibitor of apoptosis protein (IAP) is involved in apoptosis resistance against air exposure stress in crustaceans, SpIAP was cloned and investigated for the first time. The full length of SpIAP was 3351 bp, encoding a polypeptide of 662 amino acids. The predicted SpIAP protein contained three baculoviral IAP repeat domains and one really interesting new gene (RING) finger domain. Protein basic local alignment search tool and phylogenetic analysis results showed that SpIAP was clustered together with other crustaceans IAPs. SpIAP was detected in all the examined tissues and predominantly expressed in the hepatopancreas. When crabs were challenged with air exposure for 12 h, the expression level of SpIAP in the hepatopancreas was significantly increased in the experimental group compared with the control group. A RNA interference assay and flow cytometry analysis showed that when SpIAP was silenced, the cell apoptotic rate significantly increased after 24 h air exposure. These results suggested that SpIAP was involved in an anti-apoptosis response induced by air exposure in S. paramamosain.     

The effects of starvation and re-feeding on growth and swimming performance of juvenile black carp (<Emphasis Type="Italic">Mylopharyngodon piceus</Emphasis>)

We investigated the effects of starvation and re-feeding on growth and swimming performance and their relationship in juvenile black carp (Mylopharyngodon piceus). We measured the specific growth rate (SGR), resting metabolic rate (RMR) and constant acceleration test speed (U _CAT, the maximum swimming speed at exhaustion by constant acceleration test with 0.1667 cm s^?2 rate) in a treatment group (21 days of starvation then 21 days of re-feeding) and control group (routine feeding) (n = 20). Starvation resulted in a 17 % decrease in body mass of black carp (P < 0.05). After 21 days of re-feeding, body mass was greater than that of pre-starvation but still less than that of the control group at 42 days. During the re-feeding phase, the SGR of the treatment group was higher than that of the control group (P < 0.05). Starvation resulted in a significant decrease in the RMR and U _CAT. After 21 days of re-feeding, both the RMR and U _CAT recovered to the pre-starvation levels. In the control group, individual juvenile black carp displayed strong repeatability of the RMR and U _CAT across the measurement periods (P ≤ 0.002). In the treatment group, RMR showed significant repeatability between pre-starvation and re-feeding (P = 0.007), but not between pre-starvation and starvation or between starvation and re-feeding. U _CAT showed significant repeatability between pre-starvation and starvation (P = 0.006) and between pre-starvation and re-feeding (P = 0.001), but not between starvation and re-feeding. No correlation or only a weak correlation was found between any two variables of RMR, U _CAT and SGR, whereas the increment of the U _CAT (ΔU _CAT) was negatively correlated with that of SGR during the starvation phase (r = ?0.581, n = 20, P = 0.007) and re-feeding phase (r = ?0.568, n = 20, P = 0.009). This suggested that within individual black carp, there is a trade-off between growth and maintenance (or development) of swimming performance under food-limited conditions.     

Effects of temperature and fatigue on the metabolism and swimming capacity of juvenile Chinese sturgeon (<Emphasis Type="Italic">Acipenser sinensis</Emphasis>)

Chinese sturgeon (Acipenser sinensis) is a critically endangered species. A flume-type respirometer, with video, was used to conduct two consecutive stepped velocity tests at 10, 15, 20, and 25 °C. Extent of recovery was measured after the 60-min recovery period between trials, and the recovery ratio for critical swimming speed (U _crit) averaged 91.88% across temperatures. Temperature (T) effects were determined by comparing U _crit, oxygen consumption rate (MO ₂), and tail beat frequency (TBF) for each temperature. Results from the two trials were compared to determine the effect of exercise. The U _crit occurring at 15 °C in both trials was significantly higher than that at 10 and 25 °C (p < 0.05). The U _crit was plotted as a function of T and curve-fitting allowed calculation of the optimal swimming temperature 3.28 BL/s at 15.96 °C (trial 1) and 2.98 BL/s at 15.85 °C (trial 2). In trial 1, MO ₂ increased rapidly with U, but then declined sharply as swimming speed approached U _crit. In trial 2, MO ₂ increased more slowly, but continuously, to U _crit. TBF was directly proportional to U and the slope (dTBF/dU) for trial 2 was significantly lower than that for trial 1. The inverse slope (tail beats per body length, TB/BL) is a measure of swimming efficiency and the significant difference in slopes implies that the exercise training provided by trial 1 led to a significant increase in swimming efficiency in trial 2.     

Effects of nucleotides on growth performance,immune response,disease resistance and intestinal morphology in shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> fed with a low fish meal diet

Nucleotides (NT) are widely used as an immunostimulant in aquaculture. A 10-week feeding trial was conducted to evaluate the effects of dietary NT on the growth performance, immune response, disease resistance and intestinal morphology of the Pacific white shrimp Litopenaeus vannamei (initial mean body weight: 0.39 ± 0.00 g). Five isolipidic (about 7 % crude lipid) and isonitrogenous (about 39 % crude protein) practical diets were supplemented with graded levels of NT (0, 60, 90, 120 and 1200 mg kg^?1), respectively. These diets were named as N1, N2, N3, N4 and N5. Each diet was randomly fed to six tanks of shrimps, and each tank contained 40 shrimps. The shrimps were fed four times daily (07:00, 11:00, 16:00 and 21:00 h). The results showed that there were no significant differences in survival, final weight, specific growth rate, feed intake, feed conversion ratio and whole-body compositions among all the treatments (P > 0.05). Shrimps fed the control diet had the significantly lowest activities of superoxide dismutase, total nitric oxide synthase and lysozyme (P < 0.05). However, those parameters increased when dietary NT increased from 60 to 120 mg kg^?1 and decreased as inclusion level increased to 1200 mg kg^?1 (P < 0.05). The cumulative mortality of the shrimps challenged with Vibrio parahaemolyticus was significantly higher in the treatments without dietary NT supplementation than those in treatments with dietary NT (≥90 mg kg^?1) (P < 0.05). The jejunum wall thickness in shrimps fed the control diet was significantly lower than that in the treatments of N2, N3 and N4 (P < 0.05). For the villus height, the highest value (49.29 µm) was found in N3. In summary, the present study showed that 90 mg kg^?1 of dietary NT is the optimum dietary level for good gut health, immune response and disease resistance of Pacific white shrimp fed a diet with 18 % fish meal.     

Age estimation of Antarctic minke whales <Emphasis Type="Italic">Balaenoptera bonaerensis</Emphasis> based on aspartic acid racemization technique

Counting of the growth layers in the earplugs is the most accepted technique for determining chronological age of Antarctic minke whales; however, unreadable growth layers form in some individuals, especially in young animals. In this study, aspartic acid racemization (AAR) technique was developed for estimating ages in this species with the aim of complementing the age estimated using earplugs. To validate the technique and to determine the specific coefficients for age estimation, the ratio of d and l-enantiomers of aspartic acid (Asp D/L) in lens of 18 whales and 20 fetuses were analyzed and compared with earplug-based age estimates. The equation for age estimation by AAR in this species was as follows: Log_e{[1 + (Asp D/L)_act]/[1 ? (Asp D/L)_act]} = 2.30 × 10^?3 × earplug age (year) + 0.0201 (p < 0.001, r ²  = 0.918). There is a strong correlation between the age estimates by AAR and earplugs. This study was successful in developing the AAR technique for the Antarctic minke whale, and the application of this technique can complement the age estimation of this species based on earplug readings, especially for young animals with unreadable earplugs.     

Molecular cloning and expression analysis of <Emphasis Type="Italic">Megalobrama amblycephala</Emphasis> transferrin gene and effects of exposure to iron and infection with <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

Transferrin (Tf) plays an important function in iron homeostasis and metabolism of organisms. In this study, we identified and characterized the Tf gene in Megalobrama amblycephala and evaluated its expression in basal conditions as well as after iron overload and experimental infection with Aeromonas hydrophila. Furthermore, we studied the iron binding properties of recombinant Tf. The full-length M. amblycephala Tf complementary DNA (cDNA) (GenBank accession no.: KX698308) of 2245 bp was cloned and contained a 1953 bp open reading frame (ORF) encoding 650 amino acid residues and flanked by a 68 bp 5′ and a 204 bp 3′ untranslated regions (UTR). Predicted conservative structure illustrated that M. amblycephala Tf consisted of two conservative Tf domains. Amino acid sequence alignment revealed that M. amblycephala Tf had high similarity with that of cyprinids deposited in Genbank, and phylogenetic analysis showed that M. amblycephala Tf clustered with Ctenopharyngodon idella and Hypophthalmichthys molitrix. Tissue expression pattern analyses demonstrated that the liver was the main Tf mRNA expressing organ, being significantly higher than other tissues (p < 0.05). In the liver, Tf mRNA expression in fish artificially injected with the pathogenic bacteria A. hydrophila was significantly upregulated, reaching a peak at 12 h post injection (hpi) and then decreasing afterward. The expression in FeCl₃-injected fish showed a similar tendency, but reached a peak at 8 hpi. Meanwhile, fish serum iron significantly decreased following A. hydrophila injection, but increased to peak at 4 hpi and then decreased in FeCl₃-injected fish. The recombinant M. amblycephala Tf showed iron binding capacity using CAS analysis. These results are helpful to understand the structure and regulation of expression of Tf, as well as the specific function of Tf for both immune responses and iron homeostasis.     

Effects of starvation and feeding on blood chemistry,fatty acid composition and expression of vitellogenin and fatty acid-binding protein genes in female swimming crab <Emphasis Type="Italic">Portunus trituberculatus</Emphasis> broodstock

Portunus trituberculatus broodstock were stocked in plastic tanks to evaluate the effects of starvation and feeding on gonadal development, blood chemistry, fatty acid composition, and expression of vitellogenin (Vtg) and fatty acid-binding protein genes (FABP) in females. Two treatments (starved and fed) were randomly assigned to triplicate groups of 90 swimming crab broodstock (approximately 230 ± 45 g). In the starved treatment, crabs were starved for 30 days, whereas in the fed treatment crabs were fed once a day with clams. The gonadosomatic index decreased significantly in starved crabs (P < 0.05), as did the serum glucose and cholesterol concentrations; conversely, the total protein concentration in serum significantly increased (P < 0.05). In the ovary, there was a significant relative decline of 18:0, 16:1n-7 and 20:1n-9 fatty acids and relative increases of 20:4n-6, 22:6n-3, 18:1n-9 and 20:5n-3 in starved crabs compared to fed crabs (P < 0.05). Relative expression of Vtg in the ovary decreased significantly in starved crabs (P < 0.05), while there was no significant difference in hepatopancreas Vtg expression between starved and fed crabs (P > 0.05). Starvation suppressed gonadal development in female swimming crab broodstock.     

The impact of successive mass selection on population genetic structure in the Pacific oyster (<Emphasis Type="Italic">Crassostrea gigas</Emphasis>) revealed by microsatellite markers

To evaluate the impact of mass selection on genetic structure in artificially closed populations of the Pacific oyster Crassostrea gigas, we performed mass selection over six generations on two stocks from Japan and Korea and analyzed their temporal genetic variation and structure using 18 microsatellite makers, which were compared with the base populations of the two selected lines and one wild population from China. The average numbers of alleles (Na), mean observed heterozygosities (Ho), and expected heterozygosities (He) varied over generations in the two selected lines (selected lines of Japan, Na = 10.7–14.9, Ho = 0.757–0.846, He = 0.778–0.871; selected lines of Korea, Na = 9.4–17.3, Ho = 0.736–0.865, He = 0.744–0.854). There was no significant reduction in heterozygosity in the two selected lines. However, the average number of alleles per locus was significantly lower in the fifth and sixth generations of the two selected lines compared with that in the base population and wild population (P < 0.05), suggesting that the successive mass selection in closed populations may increase the sensibility of rare alleles to genetic drift. Equalizing the sex ratio of parents and reducing the selection intensity properly with the increase of selective generations is recommended to minimize the deleterious effect of genetic drift and bottleneck caused by successive mass selection. The information obtained in this study is useful for the design of appropriate management strategies for selective breeding of C. gigas.     

Rapid measurements of fat content in live and slaughtered common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

The objective of this study on common carp (Cyprinus carpio) was to obtain and predict the first cross-validated data of the fat content on market size carps using a non-invasive or non-destructive method in situ. The carps (1680 ± 388 g; n = 136) used were from a semi-intensive system and were on a different diet (cereal, pelleted and extruded diet). For the evaluation of the fat content, a Fish Fatmeter FM 692 from Distell.com. (FFM) and a manual measurement of back fat height using a digital calliper were used. For the prediction model, the following basic body measurements (variables) were used: total body length, body length, body height, the width of the body, and the circuit of the body. The body weight, weight of intestines, weight of gonads, weight of hepatopancreas, and fillet yield (%) were measured, and the Fulton coefficient was calculated. The study was focussed on evaluating the applicability of these methods and the accuracy of the obtained result, respectively. Results showed that all the rapid methods had a strong correlation. Multiple regression models with forward selection of variables were used throughout. The final prediction model between predicted and observed values for the fat content for FFM and calliper being adjusted index of determination is shown here (R _adj ²  = 0.88; 5 variables and R _adj ²  = 0.91; 7 variables), respectively.     

Effect of the early temperature on the growth of larvae and postlarvae turbot, <Emphasis Type="Italic">Scophthalmus maximus</Emphasis> L.: muscle structural and ultrastructural study

Turbot specimens were kept at three temperatures (T _s ): warm (W) (21–22 °C), ambient (A) (17–18 °C) and cold (C) (13–14 °C) during the larval and early postlarval stages. At 90 days posthatching (dph), all of them were transferred to ambient T until 190 dph. At 2–3 dph, the specimens showed a monolayer of red muscle and immature white fibres; external or dermomyotome cells (presumptive myogenic cells) were observed on the surface of the red muscle. In the following stages, many myogenic cells and presumptive myogenic precursors were observed within the myotome, presumably derived of the dermomyotome. When comparing the growth at the same age (2, 10, 25, 37 dph), the body length and the muscle growth were positively influenced by the warm T, being the hyperplasia the muscle parameter more significantly influenced. The development rate was also positively correlated with the high T: the beginning of the metamorphosis took place at 15, 23 and 25 dph at W, A and C temperatures, respectively, with the highest body length values at ambient temperature. The metamorphosis finished at 25, 30 and 37 dph at W, A and C temperatures, respectively, with the highest body length values at warm temperature. However, the muscle cellularity was similar in all the groups at the end of the metamorphosis. At 90 and 190 dph, the largest body length was observed at W temperature. However, the muscle cellularity was similar between A and W; the number of fibres was similar in all the groups at 190 dph, which shows the beginning of a compensatory muscle growth in A and C, mainly in A.     

Molecular mobility of fish flesh measured by low-field nuclear magnetic resonance (LF-NMR) relaxation: effects of freeze–thaw cycles

In this study, the molecular mobility of fish flesh was measured by low field nuclear magnetic resonance (LF-NMR) relaxation. Sardine, tuna and mackerel were frozen at ?40 °C and stored for 1 day (24 h); and then these samples were thawed at room temperature (20 °C). The relaxation of water protons in fish flesh was measured for fresh (i.e., before freezing) and multi-cycle freeze–thaw samples (i.e., up to 12 times). Three domains from different pools of protons (i.e., low-mobile, medium-mobile and high-mobile) were identified from the relaxation curve. The T _2b (low-mobile), T ₂₁ (medium-mobile) and T ₂₂ (high-mobile) indicated the proton populations in the protein molecules, strongly bound water molecules, and weakly bound water molecules, respectively. In all cases, the relaxation time (T _2b: sardine r = 0.736 and p < 0.01, tuna r = 0.857 and p < 0.001, mackerel r = 0.904 and p < 0.001; and T ₂₂: sardine r = 0.956 and p < 0.0001, tuna r = 0.927 and p < 0.0001, mackerel r = 0.890 and p < 0.0001) increased with the freeze–thaw cycles and it reached a nearly constant value after 6 freeze–thaw cycles. The increased relaxation time (i.e., higher mobility) up to 6 freeze–thaw cycles could be due to the increase in proton mobility. However, relaxation time (T ₂₁: sardine r = ?0.510 and p > 0.05, tuna r = 0.162 and p > 0.5, mackerel r = 0.513 and p > 0.01) showed insignificant change with the increase of freeze–thaw cycles, which indicated minimal change in the medium-mobile protons. The results in this study revealed that the changes in proton mobility in the fish flesh during freeze–thaw cycles could be identified using T _2b and T ₂₂ relaxation of LF-NMR.