RNA-DNA Ratio Research Articles

Nutritional evaluation of protein isolate from neem seed cake in Labeo rohita (Hamilton, 1822) fingerlings concomitant with oil extraction processing industry

A protein isolate was prepared from the neem seed cake, a by-product of the oil extraction processing industry. With this, the study aimed to assess the effects of dietary neem seed protein isolate (NPI) on growth, nutrient utilization, physio-metabolic responses, and hepatic IGF-I expression of Labeo rohita fingerlings. Five isonitrogenous (270 g/kg crude protein as fed basis) and isocaloric (3800 kcal gross energy/kg as fed basis) experimental diets were formulated with graded level of NPI by replacing soy protein isolate (SPI) on protein equivalent basis. Thus experimental diets viz., control (0 g/kg NPI, 200 g/kg SPI protein), NPI-25 (56 g/kg NPI in replacement of 250 g/kg SPI protein), NPI-50 (110 g/kg NPI in replacement of 500 g/kg SPI protein), NPI-75 (164 g/kg NPI in replacement of 750 g/kg SPI protein), NPI-100 (217 g/kg NPI in replacement of 1000 g/kg SPI protein) were prepared for conducting the feeding trial. One hundred eighty acclimated Labeo rohita fingerlings (3.5. ± .0.2 g mean weight) were equally assigned to five experimental groups in triplicates following the completely randomized design. Fishes were maintained and fed twice daily to the satiation level during the experimental period of 60 days. The study results showed that percent weight gain, protein efficiency ratio, and feed conversion ratio were significantly (P < 0.05) affected by the dietary NPI in overall and linearly. Recorded values of these parameters in the control group were not significantly (P> 0.05) different from the treatment groups except for NPI-100, which showed a significant (P < 0.05) performance retardation. Hepato-somatic index and intestinal somatic index did not vary significantly (P> 0.05) among the experimental groups. A significantly (P < 0.05) higher apparent digestibility coefficients (ADCs) value for dry matter were found in NPI-25 group than all other experimental groups. However, the inclusion of NPI did not make any significant variation in intestinal amylase and lipase enzymes' activity though protease activity differed significantly (P < 0.05) in overall as well as linearly and quadratically. The growth regulatory gene IGF-I expression and RNA-DNA ratio of the treatment groups excluding NPI-100 exhibited a similar propensity with the control group, and showed a similar linear correlation with the growth performance. Hence, the study concludes that 750 g/kg of SPI protein at 200 g/kg inclusion level can be replaced with the inclusion of 164 g/kg NPI in the diet of Labeo rohita fingerlings while maintaining the analogous (P> 0.05) growth performances.

RNA/DNA ratio to assess the growth performance in postlarvae of the pearl oyster Pinctada fucata (Gould, 1850)

RNA/DNA ratio (RDR) has been reported to be a feasible biochemical indicator for measuring the growth of numerous aquatic animal species. Nevertheless, its applicability has not been investigated to date in the pearl oyster Pinctada fucata (Gould, 1850). A laboratory experiment was undertaken to determine the relationship between RDR and growth rate in P. fucata postlarvae. The face-centered central composite design was used with three important factors (temperature, algal concentration and stocking density) simultaneously varied to produce a variety of growth rates. Temperature ranged between 18 and 34 °C, algal concentration between 5 and 100 cells μL―1, stocking density between 0.2 and 2.5 in.. mL―1. Postlarvae were fed with a 1: 1 mixture of Isochrysis zhanjiangensis and Pavlova viridis over the course of experiment. Results showed that RDR was affected significantly by the first- and second-order effects of and first-order interactions among three factors, but the interactions were negative to the growth of pearl oyster postlarvae. Within the ranges of three factors examined, algal concentration was most important, followed by temperature in influencing the growth of P. fucata postlarvae. RDR was highly positively correlated with specific growth rate (SGR) and absolute growth rate (AGR). Simple linear regression equations of shell height-based growth rates regarding RDR were established, SGR (% d―1) = ―0.05 + 2.01RDR (R2 = 0.98); AGR (μm d―1) = ―0.02 + 2.82RDR (R2 = 0.96). Lack-of-fit test indicated their high adequacy. The models have greater advantages over conventional means of assessing somatic growth, and can be utilized to reliably evaluate recent growth of P. fucata postlarvae under concurrent variations of three factors examined in the present study.

Effects of dietary magnesium supplementation on growth, feed utilization, nucleic acid ratio and antioxidant status of fingerling Heteropneustes fossilis

To investigate the effects of dietary magnesium on growth, feed utilization, nucleic acid ratio and antioxidant status of Heteropneustes fossilis and determine the optimum dietary magnesium requirement, basal diet (400 g/kg crude protein and 17.89 MJ/kg gross energy) supplemented with magnesium sulfate at 0, 2.02, 4.05, 6.08, 8.11 and 10.14 g/kg diet, yielding 0, 0.20, 0.40, 0.60, 0.80 and 1.0 g magnesium per kg of the diet were fed to triplicate groups of fishes. Analyzed values of dietary magnesium were found to be 0.06, 0.28, 0.45, 0.68, 0.88 and 1.05 g/kg. Increasing dietary magnesium levels significantly (P < 0.05) enhanced the absolute weight gain (AWG), specific growth rate (SGR), RNA-DNA ratio, protein retention efficiency (PRE) and protein gain (PG) up to 0.68 g/kg. Biometric indices were also found to improve up to 0.68 g/kg magnesium and then remained static. Antioxidant status in terms of superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) also exhibited significant improvement (P < 0.05) in response to incremental levels of dietary magnesium up to 0.68 g/kg. The whole-body composition also reflected significant changes up to magnesium level of 0.68 g/kg diet. Serum alkaline phosphatase (ALP) activity and magnesium concentration improved with the increasing magnesium level up to 0.88 g/kg diet. Improvement in whole-body and vertebrae mineralization in response to increasing dietary magnesium levels was also noted up to 0.88 g/kg diet. Broken-line regression analysis of SGR, PG, RNA-DNA ratio, serum SOD activity and vertebrae magnesium data against increasing levels of dietary magnesium indicated the optimum requirement of H. fossilis in the range of 0.65−0.79 g/kg diet.

Karanj protein isolate prepared from karanj seed cake: Effect on growth, body composition and physiometabolic responses inLabeo rohitafingerlings

A protein isolate was prepared from karanj seed (KPI) with 921.2 g protein/kg seed, which contained a negligible amount of anti‐nutritional factors and a balanced amino acid composition, especially rich in methionine. For 60‐day feeding trial, five isonitrogenous (300 g/kg CP) and isocaloric (15 MJ DE/kg) diets were formulated by replacing soybean protein isolate (SPI) on protein equivalent basis, KPI‐0 (control, 0 g/kg KPI); KPI‐25 (replacing 250 g/kg SPI protein with KPI); KPI‐50 (replacing 500 g/kg SPI protein with KPI); KPI‐75 (replacing 750 g/kg SPI protein with KPI) and KPI‐100 (replacing 1,000 g/kg SPI protein with KPI) for the feeding of L. rohita. The weight gain percentage, specific growth rate, feed conversion ratio and protein efficiency ratio were not significantly (p > .05) varied among the KPI fed and control groups. A significantly higher hepatosomatic index was recorded in the control and KPI‐25 groups compared with other groups. The whole‐body compositions, except ether extract, did not differ significantly (p > .05) among the groups. Digestive (amylase, protease, lipase and alkaline phosphatase) and metabolic enzyme activities (hexokinase, transaminases and lactate dehydrogenase) and glycogen stores were not significantly affected, whereas intestinal alkaline phosphatase differed significantly (p < .05). The RNA–DNA ratio was significantly (p < .05) higher in the KPI‐75 group. Thus, the study revealed that KPI can completely replace SPI protein at 191 g/kg inclusion level in the diets of L. rohita fingerlings.

Optimum utilization of Hygrophila spinosa leaf meal in the diet of Labeo rohita (Hamilton, 1822) fingerlings

A 60-day feeding trial was conducted to study the optimum dietary inclusion of Hygrophila spinosa leaf meal (HSLM) as a replacer of de-oiled rice bran (DORB) in the diet of Labeo rohita (rohu) fingerlings. Eight iso-nitrogenous (31% crude protein) and iso-caloric (330 Kcal DE/100 g) experimental diets were prepared with inclusion of graded level of HSLM with or without supplementation of 0.1% exogenous xylanase and cellulase enzyme (EE) viz.- C, control (0% HSLM), LM10 (10% HSLM), LM20 (20% HSLM), LM30 (30% HSLM), CEE (control + EE), LM10EE (LM10 + EE), LM20EE (LM20 + EE) and LM30EE (LM30 + EE). Two hundred and eighty eight (288) fingerlings were randomly distributed in eight experimental groups in triplicates. Feeding of fish were done to satiation by using respective experimental diet throughout the experimental period. Fish fed with 10% HSLM containing diet were exhibited significantly (p < 0.05) higher weight gain %, specific growth rate, RNA content and RNA-DNA ratio in comparison to control. However, 20% and 30% HSLM fed groups were found to be non-significant (p > 0.05) with the control group. Further supplementation of the exogenous enzyme in the leaf meal-based diets (LM10EE, LM20EE and LM30EE) could not improve the growth performance of fish significantly in compared to their non-supplemented counterparts (LM10, LM20 and LM30). Experimental groups except LM30 showed significantly (p < 0.05) higher amylase activity with the control. Addition of exogenous enzyme in rohu diets were significantly increased the muscle AST (LM10EE, LM20EE) and ALT (LM20EE, LM30EE) activities in compared to non-supplemented counterparts. The present study concludes that 30% HSLM can be incorporated in the diet of rohu with complete replacement of DORB. However, the exogenous carbohydrase supplementation in the HSLM-based rohu diet could not result extra benefit in fish in terms of growth.

Are the RNA:DNA ratio and dry-weight-at-length suitable growth proxies for brown shrimps (&lt;em&gt;Crangon crangon&lt;/em&gt;)?

Growth rates are of fundamental interest for studying population dynamics of species when no age information is available. In these cases in situ growth proxies must be identified and validated, and here we tested whether RNA-DNA ratio (RD) and dry weight condition (DWC) can act as such proxies for the shrimp Crangon crangon. Growth rates (mm d–1) were determined for male and female shrimps (20 to 67 mm) reared at five different temperatures (5°C to 25°C) and caught in two different months (May, July). Due to the potential interactive effects of the factors sex, size, temperature and time, different statistical analysis were applied to test for linear interactions (factorial analysis of mixed data, FAMDs), nonlinear additive effects (generalized additive models, GAMs) and nonlinear interactions (nonlinear regression combined with GAMs). The FAMD indicated positive correlations between length, month and growth rate. A positive correlation between DWC and sex and between RD and temperature was also indicated. RD was not significant in the GAM but a nonlinear link between length, temperature and growth was found. Finally, an extended Bertalanffy growth model was fitted to sex-specific growth rates and in a second step a GAM was fitted to the differences (residuals) between observed and predicted growth. RD again had no significant explanatory power for growth and, although it is a commonly used growth proxy, we concluded that it is not a suitable index for evaluating length growth of C. crangon.

Linking rates of metabolism and growth in marine fish larvae

The intricate relationship between metabolism and growth is still largely unexplored in early life stages of fish. In the present study, two experiments were conducted to explore how standard metabolic rate (SMR) of Atlantic herring (Clupea harengus) larvae was related to differences in body size, growth rate and feeding environment. In two of the three trials of the first experiment, larval SMR decreased (up to 37%) after larvae experienced 3 days of sub-optimal feeding conditions. Inter-individual differences in SMR and nutritional condition (RNA–DNA ratio) were unrelated. In a second experiment, inter-individual differences in SMR were not explained by differences in short-term (otolith marginal increment width) or long-term (size-at-age, otolith diameter-at-age) growth indicators in well (ad libitum) fed larvae. Nevertheless, a negative relationship between SMR and otolith core diameter (formed between hatching and first feeding) was observed. In well-fed larvae, the relationship between SMR, temperature (T, 5–15 °C) and dry mass (DM, 60–3000 µm, 10–24 mm body length) was equal to: SMR = 0.0528 (± 0.0047) * DM 0.8859 (± 0.0127) * e T * 0.1046 (± 0.0034) [mean (± SE), adj R 2 = 0.9302, n = 384]. This is the first study to report the effects of DM on SMR in Atlantic herring larvae over a wide range of T. The present results suggest that metabolic flexibility can exist, particularly when larvae experience contrasting feeding environments, which needs to be taken into account when evaluating factors affecting larval growth and survival in the sea.

Oxidative stress and RNA DNA ratio following longline capture in the silky shark Carchahrinus falciformis (Muller and Henle, 1839)

This study used transcriptomics tracers and measurements of oxidative stress to examine the effect of capture by longline on the silky shark Carcharhinus falciformis . From February 2010 to May 2012, C. falciformis individuals captured in the eastern Pacific Ocean were initially examined for sex, degree of maturity, and morphometric data. Samples were then taken from muscle tissue to determine RNA, DNA, and protein concentrations as well as RNA/DNA and protein/DNA ratios. The levels of three oxidative stress indicators [superoxide dismutase (SOD), glutathione (GSH), and malondialdehyde (MDA)] were determined in muscle. The analysis of the 159 specimens (93 juveniles and 66 adults) showed low RNA/DNA ratios at the different stages of maturity. This basal level of transcriptomics capacity may have been caused by the physiological stress resulting from capture. In juveniles, the low RNA/DNA and protein/DNA ratios were associated with low levels of cellular damage related to oxidative stress, whereas in adults the level of cell damage due to oxidative stress was high, especially in older females. This pattern indicated decreased antioxidant response capacity with increasing age in elasmobranchs

Inclusion level of deoiled rice bran (DORB) in the diet of Labeo rohita (Hamilton, 1882) fingerlings: Effect on growth and gene expression of IGF-I and IGF-II

A 60-day feeding trial was conducted to evaluate the effect of deoiled rice bran (DORB) on the growth performance and liver IGF-I and IGF-II mRNA expression in a freshwater fish, Labeo rohita. Six isonitrogenous (30%), isolipidic (6%) and iso-energetic (1.8MJ/100g) diets were prepared with different inclusion level of DORB viz., C (control, 0%), T20 (20%), T30 (30%), T40 (40%), T50 (50%) and T60 (60%). Three hundred and fifteen (315) fingerlings with 15 fish per tank having an average weight of 8.0±0.5g were randomly distributed in seven treatments in triplicates following a completely randomized design. At the end of the experiment, growth and nutrient utilization were evaluated in terms of weight gain% (WG %), SGR, FCR, PER, RNA/DNA ratio along with the gene expression of IGF-I and IGF-II. The weight gain % and specific growth rate were similar in 30, 40, 50 and 60% DORB fed groups, but higher (p<0.05) than the control and commercial diet fed groups. The PER (Protein Efficiency Ratio), LER (Lipid Efficiency Ratio) and FCR (Feed Conversion Ratio) were similar (p>0.05) in 30, 40, 50 and 60% DORB fed groups. The RNA-DNA ratio was significantly lower in T50 group, which was similar to T60 group. Based on second order polynomial regression analysis (y=−0.008x2+0.5227x+1.3407, R2=0.91), the expression of IGF-I was found to be maximum at 33% inclusion level. The hepatic IGF-I and IGF-II gene expression were checked using real time PCR normalised against the β-actin gene and found to be maximum at the dietary inclusion level of 33%. Hence, from these results it can be concluded that though growth rate was similar in all the groups fed with DORB at 30 to 60% of inclusion level, but an optimum inclusion level of DORB at 33% is best to support the nutrient utilization and growth performance of Labeo rohita fingerlings based on gene expression of IGFI and IGF II in liver.

The effect of light intensity on performance of larval pike-perch (Sander lucioperca)

In this work performance parameters of larval pike-perch (Sander lucioperca) reared under four different light intensities (100, 500, 1000 and 2500lx) until 21days post hatch (dph) were investigated. As performance parameters change in length and weight, swim bladder inflation, feed consumption, natural mortality, stress induced mortality and RNA-DNA ratio were measured. Aim was to investigate the influence of light intensity on pike-perch performance during the first three weeks of larval rearing. Significant differences were found in natural and stress induced mortality as well as in weight growth. No single light exposure level combined optimal performance of all tested performance parameters. Highest light intensity of 2500lx showed good weight growth but an increase in stress induced mortality. Bright light of 500 and 1000lx intensity was found to improve growth and stress mortality whereas dim light conditions of 100lx showed significantly lower natural mortality. Thus data suggested that most favorable illumination during larval pike-perch rearing comprise a tradeoff between optimal natural mortality under dim light conditions (100lx) or optimal larval growth and stress resistance under bright light conditions (500 and 1000lx). It is shown that high light intensities during larval rearing can be beneficial for pike-perch rearing if offspring supply is not limited.

Influence of saHnity and food deprivation on growth and RNA-DNA ratio in red drum Sciaenops ocellatus (Pisces: Sciaenidae)

Juvenile Red drum Sciaenops ocellatus held in 30 ppl natural seawater or fresh water were starved or fed ad libitum for su weeks, and sampled each week for growth and for determination of RNA, DNA, and protein contents of white and red muscles and liver. Specific growth Tate and condition factor were used lo compare changes in nucleic acid and protein concentrations in fish tissues. Salinity had liule effect on growth, while starvalIon caused a significant reducuon in all growth parameters and in the RNA-DNA ratio after three weeks. The RNA-DNA ralIos of red and white muscles of the fed fish were greater than those of the starved fish and also were related to specific growth Tate and fish condition factor. Nucleic acid concentralIons in liver were highly variable. Since wrute muscle predorninates and is more easily sampled in red drum than red muscle, and because it has less variable RNA-DNA ratios than liver, it is the tissue recornmended for nucleic acid analysis of physiological condition and growth.

Behavioral and physiological responses to prey match-mismatch in larval herring

The year-class success of Atlantic herring (Clupea harengus) spawning in the autumn/winter in the North Sea (NSAS stock) and in the spring in the western Baltic Sea (WBSS) appears driven by prey match-mismatch dynamics affecting the survival of larvae during the first weeks of life. To better understand and model the consequences of prey match-mismatch from an individual-based perspective, we measured aspects of the physiology and behavior of NSAS and WBSS herring larvae foraging in markedly different prey concentrations. When matched with prey (ad libitum concentrations of the copepod Acartia tonsa) larval growth, swimming activity, nutritional condition and metabolic rates were relatively high. When prey was absent (mismatch), swimming and feeding behavior rapidly declined within 2 and 4 days, for WBSS and NSAS larvae, respectively, concomitant with reductions in nutritional (RNA-DNA ratio) and somatic (weight-at-length) condition. After several days without prey, respiration measurements made on WBSS larvae suggested metabolic down-regulation (8–34%). An individual-based model depicting the time course of these Behavioral and physiological responses suggested that 25-mm larvae experiencing a mismatch would survive 25–33% (10, 7 °C) longer than 12-mm larvae. Warmer temperatures exacerbate starvation-induced decrements in performance. Without Behavioral and metabolic adjustments, survival of 25-mm larvae would be reduced from 8 to 6 days at 7 °C. Our findings highlight how adaptive Behavioral and physiological responses are tightly linked to prey match-mismatch dynamics in larval herring and how these responses can be included in models to better explore how bottom-up processes regulate larval fish growth and survival.

Maternal consumption of non‐toxic Microcystis by Daphnia magna induces tolerance to toxic Microcystis in offspring

Summary Freshwater cyanobacterial blooms are a worldwide environmental issue. These blooms often comprise both non‐toxic and toxic species and strains. Populations of some zooplankton, including Daphnia, have been shown to adapt locally to toxic Microcystis through maternal effects. However, Microcystis populations vary spatially and temporally in the absolute and relative abundances of non‐toxic and toxic genotypes. We examined variation in induction of tolerance to toxic cyanobacteria in offspring from two Daphnia magna clones (JS and AH) fed diets containing Scenedesmus by itself or in combination with either a non‐toxic or a toxic clone of Microcystis aeruginosa. The diets containing Microcystis included relatively more cyanobacteria within each week of the 3 week experiment (week 1–10%, week 2–20%, week 3–40%). Daphnia neonates were collected from these three treatments at the end of the third week and fed a diet containing Scenedesmus and toxic Microcystis for 3 weeks before a suite of life‐history, physiological and biochemical measurements were made on the surviving animals. Neonates from mothers fed toxic and non‐toxic Microcystis showed enhanced growth and reproduction compared to neonates produced from mothers fed only Scenedesmus. Our results showed that Daphnia neonates could be induced to tolerate toxic cyanobacteria when their mothers were fed diets containing non‐toxic or toxic strains of cyanobacteria. Furthermore, elevated RNA–DNA ratios, superoxide dismutase activity and catalase activity in neonates fed diets containing non‐toxic or toxic Microcystis clones suggested that the mechanisms behind these changes involved processes associated with metabolism and antioxidation. Our study shows that non‐toxic cyanobacteria can induce tolerance to toxic cyanobacteria and further elucidates the general importance of maternal effects on tolerance of cyanobacteria in herbivorous zooplankton.

Preliminary insight into the relationship between environmental factors and the nutritional condition and growth of Gilchristella aestuaria larvae in the upper reaches of South African estuaries

Estuarine systems play a critical role as nursery areas for some fish species. Nursery function, nevertheless, is likely to vary among estuaries, mostly due to differences in habitat quality. High quality nursery habitats are those in which growth and survival of early stages of fish are enhanced. The nutritional condition of larval fishes has vital implications for their mortality and growth, and thereby their recruitment. This study aimed to compare the nutritional condition of Gichristella aestuaria larvae, using individual RNA-DNA ratios and growth rates in the upper reaches of six estuaries in South Africa to find the environmental factors that better determine the nutritional condition of fish larvae. Physico-chemical factors as well as calorific value of zooplankton were used to correlate to fish body condition. Results showed that the larvae of G. aestuaria from the freshwater rich Gamtoos and the Sundays estuaries were in better nutritional condition than the larvae from other estuaries, while larvae from the Swartkops Estuary, a highly eutrophic system, presented the worst nutritional condition of all studied larvae. Salinity and the abundance of zooplankton were the major factors determining the nutritional condition of G. aestuaria larvae in these warm temperate estuaries. In addition, our results suggest that the match-mismatch hypothesis might also be important in estuarine systems. This study represents one of the few studies worldwide that applied a multispecies growth model for fish larvae in warm temperate estuaries.

Calibrating and comparing somatic-, nucleic acid-, and otolith-based indicators of growth and condition in young juvenile European sprat (Sprattus sprattus)

Reliable estimates of short- and longer-term in situ growth and condition of organisms are critical if one hopes to understand how the environment regulates survival. This study reports the first comparison of somatic- (K), biochemical- (RNA–DNA ratio, RD) and otolith- (increment widths, OIW) based indices of condition of a young juvenile fish. Measurements were made on European sprat (Sprattus sprattus) that had i) known differences in somatic growth rate caused by providing different, constant prey ration levels, ii) been fed ad libitum at 7, 11, 15, 18 and 22°C, and iii) been deprived of prey for either 4, 8 or 12days and re-fed for 8days. All three proxies explained significant amounts (70 to 90%) of the variability in measured growth rate. In fish experiencing a change in their feeding level and concomitant change in mass-at-length (K), RD tracked changes in both length and mass while OIW only tracked changes in length. Values of OIW and RD were highest at 18°C suggesting that this is the optimal temperature for growth in these juveniles. During food deprivation, RD and OIW rapidly decreased and reached their lowest values within ~4days. Upon re-feeding, RD increased most rapidly, K was most variable and the response time in OIW was slowest (two-times slower than RD). These patterns reflected preferential allocation of food energy to restore body mass in recently re-fed fish prior to fish increasing both mass and length. These results indicate that the sensitivity and applicability of growth proxies depend on the recent feeding history, that proxies have different response times, and that caution be taken when inferring growth and condition in early life stages of fishes that forage in patchy prey environments.

Dietary Administered Bacillus sp. PP9 Enhances Growth, Nutrition and Immunity in Cirrhinus mrigala (Hamilton)

Bacillus sp. PP9, a noble bacterial isolate of mrigal (Cirrhinus mrigala) gut was investigated for its efficacy as a dietary probiotic against mrigal (C. mrigala) through a dose dependent impact assessment. Mrigal fingerlings (avg.wt. 2.5 ± 0.20 g) were fed with three different doses (2 × 104, 2 × 105 and 2 × 106 CFU) of Bacillus sp. PP9 admixed with 100 g feed for a period of 60 days. It was found that the feed with Bacillus concentration of 2 × 104 CFU exhibited significantly higher growth, maximum RNA DNA ratio, lower food conversion ratio in comparison to other two feed types. Enhanced intestinal protease and α-amylase activity followed by maximum hepatic glutamic oxaloacetic transaminase and glutamate pyruvate transaminase levels were also monitored in this specific feed type. Important hematological parameters like hemoglobin percentage, total erythrocyte count, total leukocyte count, corpuscular hemoglobin also indicated a healthy trend in this dose. Furthermore, the same dietary treatment exhibited highest levels of total serum protein, albumin globulin ratio and serum bactericidal activity. The growth, nutrition and immunological parameters showed a declining trend with increase in the bacterial concentration as well as in the control group (without probiotic). In summary, dietary supplement of 2 × 104/100 g appears as a potential probiotic dose of Bacillus sp. PP9 for growth, nutritional efficacy as well as immunological modulation of C. mrigala and denotes a recommended concentration for its future field applications.

Ontogenetic changes in RNA, DNA and protein contents of Chinese loach, Paramisgurnus dabryanus (Dabry de Thiersant, 1872), larvae and juveniles

The changes in nucleic acid-based indices and protein variables of Chinese loach, Paramisgurnus dabryanus, larvae and juveniles from hatching to 60 days after hatching (DAH) were conducted to assess its growth potential. The nucleic acid contents were analysed using a UV-based method (n = 3, rearing temperature 24.4 ± 0.4°C, dissolve oxygen 7.1 ± 0.5 mg L−1, pH 7.9 ± 0.4). Ribonucleic acid (RNA) concentration significantly decreased from 2 to 5 DAH, then increased rapidly until 10 DAH, declining slightly thereafter. Deoxyribonucleic acid (DNA) concentration increased 2–5 DAH, decreased until 9 DAH, slightly increased again around 26 DAH, and then declined to a relatively stable level. Both RNA-DNA and protein-DNA ratios showed a statistically obvious relationship with growth rates. A significantly positive relationship was found between RNA-DNA ratio and growth rates during the early life stage of Chinese loach. According to the results, growth of Chinese loach is characterized by rapid hyperplasia from hatching through completion of the yolk-sac stage followed by continued rapid hyperplasia combined with increasing hypertrophy after feeding commences. The stage preceding 17 DAH of Chinese loach P. dabryanus is presumed to be critical for its survival and growth at 24°C.

Direct Effects of Microalgae and Protists on Herring (Clupea harengus) Yolk Sac Larvae.

This study investigated effects of microalgae (Rhodomonas baltica) and heterotrophic protists (Oxyrrhis marina) on the daily growth, activity, condition and feeding success of Atlantic herring (Clupea harengus) larvae from hatch, through the end of the endogenous (yolk sac) period. Yolk sac larvae were reared in the presence and absence of microplankton and, each day, groups of larvae were provided access to copepods. Larvae reared with microalgae and protists exhibited precocious (2 days earlier) and ≥ 60% increased feeding incidence on copepods compared to larvae reared in only seawater (SW). In the absence and presence of microalgae and protists, life span and growth trajectories of yolk sac larvae were similar and digestive enzyme activity (trypsin) and nutritional condition (RNA-DNA ratio) markedly declined in all larvae directly after yolk sac depletion. Thus, microplankton promoted early feeding but was not sufficient to alter life span and growth during the yolk sac phase. Given the importance of early feeding, field programs should place greater emphasis on the protozooplankton-ichthyoplankton link to better understand match-mismatch dynamics and bottom-up drivers of year class success in marine fish.

Do transparent exopolymeric particles (TEP) derived from Phaeocystis globosa bloom impact the physiological performances of European sea bass juveniles

A mesocosm experiment (1m3 enclosures) was carried out over 28days to evaluate the effect of Transparent Exopolymer Particles (TEP) derived from decaying Phaeocystis globosa colonies on the physiological performance and mortality of European sea bass juveniles (35mm in length and 113days old). Accordingly, sea bass juveniles were exposed to high TEP concentrations derived from both a culture of decaying P. globosa colonies (7634.27±3514.41μgXGeqL−1) and freshly sea foam (932.54±341.21μgXGeqL−1). During the experiment, environmental parameters (pH, dissolved oxygen, temperature and salinity) were stable, similar among treatments and not limiting for growth. Only TEP concentration varied between treatments. Fish mortality rate was relatively low (0 to 2%d−1) and mostly occurred during the first week when TEP concentrations were relatively low. Despite high and varying TEP concentrations, juvenile sea bass physiological performances (growth in length and weight, Fulton condition index and RNA–DNA ratio) did not differ between replicates and treatments. In addition, juvenile sea bass increased both in size by 7.2mm (growth rate of 0.26mmd−1) and weight by 708mg (growth rate of 25.29mgd−1) during the 28days of the experiment. Altogether, these results showed clearly that TEP derived from decaying P. globosa bloom and foam accumulation have no negative effect on juvenile sea bass physiological performances and survival if water dissolved oxygen is maintained high. Despite being one of the most recurrent phytoplankton blooms recorded in the northwest European shelf seas and forms large blooms in the coastal waters during spring, we suggest that Phaeocystis bloom has no deleterious effect on marine coastal fish aquaculture activities.

Growth energetics of juvenile herring, Clupea harengus L.: food conversion efficiency and temperature dependency of metabolic rate

Summary The relationship between rates of food consumption (C) and somatic growth (G) and the effect of temperature (T) on rates of mass lost during food deprivation were examined in 9–10 cm total length (TL) [1.0–1.5 g dry mass (DM)] juvenile Atlantic herring (Clupea harengus L.) in the laboratory. One feeding-growth trial was conducted at 16°C using groups of herring feeding on known rations of brine shrimp (Artemia spp.) nauplii to quantify gross and net growth efficiency. Rates of mass lost by groups of herring (a proxy for metabolic rate, M) were measured in trials conducted at 9.7, 14.2 and 17.9°C. Gross growth efficiency (GGE = 100*G*C−1) at 16°C was 25% at the highest rations (5.8–6.6% DM). The maintenance ration (Cmain = C at zero G) was equal to 432 J*fish−1*d−1 or 2.0% DM*d−1. At 16°C, net growth efficiency (100*G*(C−Cmain)−1) was 42%. The nucleic acid content (RNA-DNA ratio, RD) in herring muscle tissue was strongly related to somatic growth (G, % DM*d−1 = −0.36*RD2 + 3.21*RD −3.92, r2 = 0.90, P < 0.05, n = 8 groups). The effect of T (9.7–17.9°C) on M was described by a second order polynomial equation M = −1.24*T + 38.2*T − 218 (J*g DM−1*d−1) and M = −10*T + 310*T − 1815 (J*fish−1*d−1). This was the first study to investigate the influence of temperature on the metabolic rate of juvenile Atlantic herring under stress-free conditions in the laboratory and provides the first estimates of gross and net growth efficiency for this species feeding on live prey.