Community metabolism, P/R ratio and photosynthetic efficiency of a brackishwater farm

The productivity level of a brackishwater fish culture farm consisting of 25 ponds, with a water spread area of 2.5 ha, was studied. Gross community photosynthesis of the farm was found to be 46.32 Kcal/m2/day, which is equivalent to the release of 13.23 of O2/m2/day, or the fixing of 4.10 gC/m2/day. Respiratory demand of the farm was estimated to be 44.66 kcal/m2/day, which is equivalent to the uptake of 12.76 g O2/m2/day or the utilization of 3.95 gC/m2/day. Photosynthetic efficiency of the farm was high at 2.26%. The P/R ratio was 1.04, showing eutrophic nature.

Respiratory metabolism in Oreochromis mossambicus, Peters under different environmental conditions

Oxygen consumption in Oreochromis mossambicus, Peters (3-60g in weight) was measured under different stress conditions at a constant temperature of 20±1°C. The rate of oxygen consumption was significantly higher (0.170 ml gˉ¹hˉ¹)at a salinity of 30x10ˉ³ compared with that (0.132ml gˉ¹hˉ¹) in freshwater. The oxygen consumption was also found to be affected by changes in pH. Weight specific rate decreased significantly from 0.113 to 0.045 ml gˉ¹hˉ¹ with increasing body weight. A positive correlation was recorded between availability of dissolved oxygen and the rate of oxygen consumption by the fish. While copper sulphate and malachite green inhibited the respiratory metabolism, formaldehyde treatment raised it from 0.088 to 0.118ml gˉ¹hˉ¹.

Postmortem changes in hilsa fish. Pt. 1. Studies on rigor-mortis, typical yields and protein composition of dark and white muscle of hilsa fish (Tenualosa ilisha Ham.)

Hilsa (Hilsa ilisha) caught by gill net were immediately killed by cranial spiking. Three fish were kept in ice (0°C) and three other at room temperature (33°C) to follow development of rigor mortis and changes in muscle pH. The rest were frozen stored at -20°C. Rigor started 15 minutes after death in all fish and reached full rigor (100%) state in 2 and 4 hours respectively in fish kept at 33° and 0°C. The fish at 33°C deteriorated 16 hours after while in full rigor but those at 0°C lasted 26 hours of death without deterioration. Freshly caught hilsa had a muscle pH around 7 which decreased with time rapidly at 33°C and slowly at 0°C. The relative proportion of protein fraction in white and dark muscle of fish stored at 0°C and -20°C were also studied. The proportion of dark muscle was 30.34% of the white muscle. White muscle in fish at 0°C was found to contain 32.0% sarcoplasmic, 57.6% myofibrilla, 9.4% alkali-soluble and 1.1% stroma protein whereas these proteins in dark muscle were 29.9%, 58.4%, 9.8% and 1.9% respectively. The protein fractions of white muscle in frozen-fish were found 27.6% sarcoplasmic, 64.7% myofibrilla, 6.0% alkali-soluble and 1.7% of stroma protein whereas they were 30.6%, 58.6%, 8.9 and 1.9% for dark muscle. Some changes occurred in protein composition during frozen storage. The relative amounts of sarcoplasmic, alkali soluble and stroma protein fractions decreased while myofibrilla fraction increased in frozen condition. This may be attributed to drip loss of soluble protein during thawing.

Postmortem changes in hilsa fish. Pt. 2. Studies on physical and bacteriological changes in iced and frozen stored hilsa fish (Tenualosa ilisha Ham.)

Studies were conducted to evaluate the quality of hilsa fish during icing and freezing storage at -20°C by determining organoleptic and bacteriological aspects. The fishes stored in ice were organoleptically in acceptable condition 2 for 20 days. The bacterial load in muscles of 4 days ice stored fish was 2.5x10² CFU/g which gradually increased up to 1.8x10⁵ CFU/g after 20 days when the fishes were organoleptically in acceptable condition. The keeping qualities of different days of ice stored fishes were also evaluated during their subsequent frozen storage at -20°C. Both 4 and 7 days of ice stored fishes were organoleptically in acceptable condition up to 48 weeks but the highest degree of freshness was found for fish stored in ice for 4 days before freezing at -20°C. The result indicates that the longer is the duration of ice storage before freezing, the shorter is the shelf life of the fish. The initial bacterial load prior to freezing of the 4 and 7 days of ice stored samples were 2.5x10³ CFU/g and 3.8x10⁴ CFU/g, respectively which reduced to 2.21x10² CFU/g and 2.38x10² CFU/g, respectively at the end of the 24 weeks of frozen storage. However, after 40 weeks the bacterial load in the frozen stored sample fell below the detection level.

Energetics of resting metabolism in an Indian major carp (Catla catla Ham.)

Resting metabolism in Indian major carp, Catla catla Ham. fingerlings were investigated. For this purpose a water recirculatory system in the laboratory was used. The metabolic energy losses were determined by the indirect method of oxygen consumption by the fish and were then multiplied by an oxycalorific coefficient (Q-ox). Five metabolism chambers in the experimental system were used where there were two same treatment runs in quadruplicate of mean total weight of fish fingerlings of 109.5, 110.4, 112.8 and 111.6g/chamber. The water temperature in the system was 28±0.5°C. The mean metabolic rate in the replicates showed no significant variation (p>0.05) and was found to be 151.66, 153.91, 150.25, 152.74 mgO-2/kg/h respectively. This showed an equivalent energy loss 5.40, 5.52, 5.51 and 5.56 KJ/chamber/day (35.60, 35.92, 36.67 and 36.40 KJ/kg/day) respectively. Energetics of resting metabolism in an Indian major carp (Catla catla Ham.)

Feeding metabolism in an Indian major carp (Catla catla Lin.) fed on different protein diets

Feeding metabolism in an Indian major carp, Catla catla fingerlings of 10.8+0.56g was investigated in a flow-through water recirculating system. The metabolic energy loss in resting metabolism and feeding metabolism were determined by the indirect method of oxygen consumption followed by multiplication by suitable oxycalorific coefficient. This was done in four metabolic chambers of a respirometer system. Ten fish fingerlings of mean total weight of 109.5, 110.4 and 112.8g/chambers respectively each in two experimental runs of three treatments a, b and c were used. The mean resting metabolic rate during unfed condition showed no significant variation in different treatments. The fish in three treatments a, b and c fed on diets containing 28, 33 and 38% crude protein had significantly different (p<0.05) post-fed SDA magnitude of 497.7, 638.7 and 735.5 mgO2/chamber/day having an equivalent energy loss of 12.68, 14.68 and 15.86 KJ respectively. The SDA co-efficient in three treatments a, b and c were 14.95, 19.00 and 22.36% respectively whereas, respiratory energy - 'R' as % of mean total ingested energy in three treatments were 26.93, 31.17 and 34.74% respectively showing a significant increase (p<0.05) with increase of protein. Feeding metabolism in an Indian major carp (Catla catla Lin.) fed on different protein diets.

Role of RNA polymerase IV in plant small RNA metabolism.

In addition to the three RNA polymerases (RNAP I-III) shared by all eukaryotic organisms, plant genomes encode a fourth RNAP (RNAP IV) that appears to be specialized in the production of siRNAs. Available data support a model in which dsRNAs are generated by RNAP IV and RNA-dependent RNAP 2 (RDR2) and processed by DICER (DCL) enzymes into 21- to 24-nt siRNAs, which are associated with different ARGONAUTE (AGO) proteins for transcriptional or posttranscriptional gene silencing. However, it is not yet clear what fraction of genomic siRNA production is RNAP IV-dependent, and to what extent these siRNAs are preferentially processed by certain DCL(s) or associated with specific AGOs for distinct downstream functions. To address these questions on a genome-wide scale, we sequenced approximately 335,000 siRNAs from wild-type and RNAP IV mutant Arabidopsis plants by using 454 technology. The results show that RNAP IV is required for the production of >90% of all siRNAs, which are faithfully produced from a discrete set of genomic loci. Comparisons of these siRNAs with those accumulated in rdr2 and dcl2 dcl3 dcl4 and those associated with AGO1 and AGO4 provide important information regarding the processing, channeling, and functions of plant siRNAs. We also describe a class of RNAP IV-independent siRNAs produced from endogenous single-stranded hairpin RNA precursors.

Adaptive evolution of energy metabolism genes and the origin of flight in bats

Bat flight poses intriguing questions about how flight independently developed in mammals. Flight is among the most energy-consuming activities. Thus, we deduced that changes in energy metabolism must be a primary factor in the origin of flight in bats. The respiratory chain of the mitochondrial produces 95% of the adenosine triphosphate (ATP) needed for locomotion. Because the respiratory chain has a dual genetic foundation, with genes encoded by both the mitochondrial and nuclear genomes, we examined both genomes to gain insights into the evolution of flight within mammals. Evidence for positive selection was detected in 23.08% of the mitochondrial-encoded and 4.90% of nuclear-encoded oxidative phosphorylation (OXPHOS) genes, but in only 2.25% of the nuclear-encoded nonrespiratory genes that function in mitochondria or 1.005% of other nuclear genes in bats. To address the caveat that the two available bat genomes are of only draft quality, we resequenced 77 OXPHOS genes from four species of bats. The analysis of the resequenced gene data are in agreement with our conclusion that a significantly higher proportion of genes involved in energy metabolism, compared with background genes, show evidence of adaptive evolution specific on the common ancestral bat lineage. Both mitochondrial and nuclear-encoded OXPHOS genes display evidence of adaptive evolution along the common ancestral branch of bats, supporting our hypothesis that genes involved in energy metabolism were targets of natural selection and allowed adaptation to the huge change in energy demand that were required during the origin of flight.

Effect of dietary linolenic acid/linoleic acid ratio on growth performance, hepatic fatty acid profiles and intermediary metabolism of juvenile yellow catfish Pelteobagrus fulvidraco

The present study aimed to evaluate the effect of dietary linolenic acid (LNA)linoleic acid (LA) ratio on growth performance, hepatic fatty acid profile and intermediary metabolism of juvenile yellow catfish Pelteobagrus fulvidraco. Six isonitrogenous and isolipidic diets were formulated to contain incremental levels of LNA from 0 to 5% at the expense of corn oil (rich in LA), resulting in six dietary treatments with LNA to LA ratios ranging from 0.35 to 14.64. The experiment continued for 7 weeks. Best growth and feed intake were obtained in the fish fed the diets containing the LNA/LA ratios of 1.17 and 2.12 (P<0.05). In contrast, feed conversion ratio was the lowest for fish fed the diets containing the LNA/LA ratios of 1.17 and 2.12 (P<0.05). Dietary LNA to LA ratios significantly influenced viscerosomatic index and hepatosomatic index (P<0.05), but not condition factor (P>0.05). Body composition was also significantly influenced by dietary LNA to LA ratios (P<0.05). Generally, liver FA compositions reflected dietary FA profiles. Declining LA and increasing LNA contents in liver were observed with the increasing dietary LNA/LA ratios (P<0.05). Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased with the increasing LNA to LA ratios, suggesting that yellow catfish could elongate and desaturate C18 polyunsaturated fatty acids into highly unsaturated fatty acids. As a consequence, the n-6 fatty acids (FA) declined, and total n-3 FA and n-3/n-6 ratios increased with the dietary ratios of LNA/LA (P<0.05). Dietary LNA to LA ratios significantly influenced several enzymatic activities involved in liver intermediary metabolism (P<0.05), such as lipoprotein lipase, hepatic lipase, pyruvate kinase, succinate dehydrogenase, malic dehydrogenase and lactate dehydrogenase, suggesting that dietary LNA/LA ratios had significant effects on nutrient metabolism in the liver. To our knowledge this is the first demonstration of the effects of dietary LNA to LA ratios on the enzymatic activities of liver in fish, which provides information on diet quality and utilization, and can also be used as an indicator of the nutritional status of this fish. (C) 2009 Elsevier B.V. All rights reserved.

Comparative studies on photosynthesis and phosphate metabolism of Cylindrospermopsis raciborskii with Microcystis aeruginosa and Aphanizomenon flos-aquae

The physiological differences for three bloom-forming cyanobacteria (Cylindrospermopsis raciborskii, Microcystis aeruginosa, and Aphanizomenon flos-aquae) were investigated. In comparison with M. aeruginosa and A. flos-aquae, C. raciborskii exhibited a significantly higher concentration of carotenoids, higher values in maximum photosynthesis rate (P-m), apparent photosynthetic efficieny (a), and maximum electron transport rate (ETRmax) during the growth period. In addition, higher extracellular alkaline phosphatase activities and lower light compensation point (I-c) were also detected in C raciborskii (p < 0.05, ANOVA). Therefore, it is suggested that the higher photosynthetic activities, more effective uptake and utilization to phosphate, and low light requirements might play important roles in the occurrence and invasive behavior of C. raciborskii. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

Carbon and nitrogen metabolism of an eutrophication tolerative macrophyte, Potamogeton crispus, under NH4+ stress and low light availability

Submersed macrophytes in eutrophic lakes often experience high NH4+ concentration and low light availability in the water column. This study found that an NH4+-N concentration of 1 mgL(-1) in the water column apparently caused physiological stress on the macrophyte Potamogeton crispus; L The plants accumulated free amino acids (FAA) and lost soluble carbohydrates (SC) under NH4+ stress. These stressful effects of NH4+ were exacerbated under low light availability. Shading significantly increased NH4+ and FAA contents and dramatically decreased SC and starch contents in the plant shoots. At an NH4+-N concentration of 1 mg L-1 in the water column, neither growth inhibition nor NH4+ accumulation was observed in the plant tissues of P. crispus under normal light availability. The results showed that 1 mg L-1 NH4+-N in the water column was not toxic to P. crispus in a short term. To avoid NH4+ toxicity. active NH4+ transportation out of the cell may cost energy and thus result in a decline of carbohydrate. When NH4+ inescapably accumulates in the plant cell, i.e. under NH4+ Stress and shading, NH4+ is scavenged by FAA synthesis. (c) 2009 Published by Elsevier B.V.