Growth of a grazing phytoplanktivorous fish and growth enhancement of the grazed alga

Summary The blue tilapia, Tilapia aurea, consumes the green alga, Ankistrodesmus falcatus, with some algal cells passing through the gut in viable condition. Grazing fish grew and the grazed algal populations had enhanced densities compared to ungrazed populations. Algal growth enhancement was not produced by either bacteria or fish excreting an algal limiting nutrient. Possible ingestion and digestion of bacterial cells by the fish might release nutrients to the algal cells that were otherwise unavailable. Blue tilapia may be affecting algal communities in ways other than by passive size selection. Enhancement of algal growth by the blue tilapia could have important implications for understanding the phytoplankton dynamics in waters containing blue tilapia.     

Nitrogen budgets of urban lawns under three different management regimes in southern California

We constructed nitrogen (N) budgets for the lawns of three simulated residences built to test the environmental impacts of three different residential landscape designs in southern California. The three designs included: a “Typical” lawn planted with cool season tall fescue (Schedonorus phoenix), fertilized at the recommended rate for this species (192 kg^?1 ha^?1 year^?1) and irrigated with an automatic timer; a design intended to lower N and water requirements (“Low Input”) with the warm season seashore paspalum (Paspalum vaginatum) fertilized at 123 kg^?1 ha^?1 year^?1 and irrigated with a soil moisture-based system; and a design incorporating local best practices (“Low Impact” lawn) that included the native sedge species Carex, fertilized at 48 kg^?1 ha^?1 year^?1 and irrigated by a weather station-based system. Plant N uptake accounted for 33.2 ± 0.5 (tall fescue), 53.7 ± 0.7 (seashore paspalum), and 12.2 ± 1.3 % (Carex) of annual N inputs, while estimated N retention in soil was relatively large and similar in the three lawns (41–46 %). At lower N and water inputs than Typical, Low Input showed the highest annual clipping yield and N uptake, although it also had higher denitrification rates. Leaching inorganic N losses remained low even from the Typical lawn (2 %), while gaseous N losses were highly variable. The Low Input lawn was most efficient in retaining N with relatively low water and N costs, although its fertilization rates could be further reduced to lower gaseous N losses. Our results suggest that the choice of a warm-season, C₄ turf species with reduced rates of irrigation and fertilization is effective in this semi-arid region to maintain high productivity and N retention in plants and soils at low N and water inputs.     

Dry-matter budgets for Diacrisia casignetum larvae fed on sunflower leaves

Larvae of Diacrisia casignetum Kollar were reared in groups of 100, 50 and 10 on fresh sunflower leaves at 27 ± 1°C temperature, 75 ± 5% r.h. and 12 h light each day. Rates of feeding, excretion and weight gain increased with age of the larva and were greatest in the sixth instar. Differences in these rates attributable to density were statistically heterogeneous (P < 0.001) whereas, of those attributable to instar, the weight gain was significant (P < 0.10). The second-instar larvae had highest levels of protein and carbohydrates in the body tissues; and the sixth-instar larvae had, the least. The pattern of protein assimilation in various instars was similar to that of glycogen except that proportional differences in the latter were pronounced in fifth and sixth instars. Consumption index, growth rate and approximate digestibility were high in the early instars whereas efficiencies of conversion of ingested and digested food were high in advanced instars. Food utilization, as reflected by efficiency of conversion of ingested and digested values in advanced instars, indicated the amount needed for maintenance decreased and more energy was left for growth and reproduction.     

Nitrogen budgets for three cropping systems fertilised with cattle manure

A field plot experiment was set up on a sandy loam soil of SW England in order to determine the efficiency of nitrogen use from different cattle manures. The manure treatments were low and high dry matter cattle slurries and one farmyard manure applied at a target rate of 200 kg total N ha(-1)year(-1), and an untreated control. There were three different cropping systems: ryegrass/clover mixture, maize/rye and maize/bare soil, which were evaluated during 1998/99 and 1999/00. Measurements were made of N losses, N uptake and herbage DM yields. Result showed that manure type had a significant effect on N utilisation only for maize. N balances were negative in maize (approximately -247 to -10 kg N) compared to grass (approximately 5-158 kg N). Agronomic management was more important than manure type in influencing N losses, where soil cultivation appeared to be a key factor when comparing maize and grass systems.     

Lipids in Acanthodiaptomus denticomis during starvation and fed on three different algae

Variations in the levels of triglycerides, wax esters and polarlipids were determined in adults of the calanoid copepod Acanthodiaptomusdenticornis when freshly caught, starved or fed on the followingalgae: Anabaena spiroides, Cyclotella pseudostelligera and Pediastrumduplex. Over 7 days starvation, triglycerides and wax esterswere almost entirely used up by the copepods. Subsequent feedingover 20 days partially restored triglycerides but restored onlya relatively small fraction (<20%) of wax esters in the animals.Differences in the lipid restoration were found: the restoredtriglyceride level was higher in animals feeding on Cyclotellapseudostelligera or Pediastrum duplex than in those feedingon Anabaena spiroides. Fatty acid composition of neutral lipidswas closely linked to fatty acid composition of algae. The resultssuggest that lipid and fatty acid contents of Acanthodiaptomusdenticornis are good indices of the copepod's nutritional statusand short-term (0–20 days) feeding history.     

Density and size distribution of Daphnia populations at different fish predation levels

Density and size structure changes of natural daphniids populations were studied in enclosures with a different level of fish predation. Daphnia pulicaria was totaly removed in high predation variants, and the differences of the mean body length both in adults and juveniles are apparent between low predation enclosure and enclosure without fish. Daphnia galeata was replaced by D. magna and D. pulicaria in the enclosure without fish. The decline of densities and the substantial (30–50%) and fast (during 12 days) shift of mean body length both in adults and juveniles of D. galeata was induced by the fish (carp fry) introduction to the high predation enclosures.     

Anglers' records as a tool for assessing changes in fish populations

Published anglers’ records from Polish rivers between 1966–1991 were used to show shifts in body weight of two obligatory riverine species: barbel [Barbus barbus(L.)], and chub [Leuciscus cephalus (L.)]. The body weight of barbel significantly decreased while that of chub did not. In 1966–89, the quality of inland waters continuously decreased, a result mainly from nutrient element input (domestic and agricultural). Hence, we consider two factors which were mainly responsible for reduction in fish size: overfishing and, perhaps, eutrophication.     

Morphometric variation of snakehead fish,Channa punctatus,populations from three Indian rivers

The present study was undertaken with the objective to investigate the intraspecific variation of Channa punctatus on the basis of morphometric characters using the truss network system that was constructed from the fish body. Fish samples were collected from the Narora (n = 62) and Kanpur sites (n = 46) of the Ganga River, the Firozabad site in the Yamuna River (n = 66) and at the Lucknow site of the Gomti River (n = 60). Data were subjected to principal component analysis, discriminant function analysis and univariate analysis of variance. The first principal component (PC I) analysis explained 47.75% of total variation while PC II and PC III explained 8.18 and 7.48%, respectively. The step‐wise discriminant function analysis retained seven variables that significantly discriminated the populations. Using these variables 81.85% of the original groups were classified into their correct samples. Misclassification was higher for the samples from Ganga River (19.6% at the Kanpur site and 19.4% for the Narora site). Of the total 27 transformed morphometric measurements, 23 exhibited significant differences among the populations. These findings indicate the presence of different stocks of fish from the three rivers.     

Determination of beta-defensin genomic copy number in different populations: a comparison of three methods

Background

There have been conflicting reports in the literature on association of gene copy number with disease, including CCL3L1 and HIV susceptibility, and β-defensins and Crohn''s disease. Quantification of precise gene copy numbers is important in order to define any association of gene copy number with disease. At present, real-time quantitative PCR (QPCR) is the most commonly used method to determine gene copy number, however the Paralogue Ratio Test (PRT) is being used in more and more laboratories.

Findings

In this study we compare a Pyrosequencing-based Paralogue Ratio Test (PPRT) for determining beta-defensin gene copy number with two currently used methods for gene copy number determination, QPCR and triplex PRT by typing five different cohorts (UK, Danish, Portuguese, Ghanaian and Czech) of DNA from a total of 576 healthy individuals. We found a systematic measurement bias between DNA cohorts revealed by QPCR, but not by the PRT-based methods. Using PRT, copy number ranged from 2 to 9 copies, with a modal copy number of 4 in all populations.

Conclusions

QPCR is very sensitive to quality of the template DNA, generating systematic biases that could produce false-positive or negative disease associations. Both triplex PRT and PPRT do not show this systematic bias, and type copy number within the correct range, although triplex PRT appears to be a more precise and accurate method to type beta-defensin copy number.     

Application of phytoremediation technology in decontamination of a fish culture pond fed with coal mine effluent using three aquatic macrophytes

Abstract

In the present study, three aquatic macrophytes, Eichhornia crassipes, Salvinia molesta, and Pistia stratiotes were used to assess their relative efficacies in decontamination of a fish culture pond, regularly fed with coal mine effluent (CME). The level of metals like Fe, Mn, Ni, Zn, Cu, Pb, Cr, and Cd were much higher in CME-fed pond water than their recommended limits in drinking water set by the Bureau of Indian standards and in effluents by the Environmental Protection Agency. The levels of metal were lowered substantially in CME-fed pond water after exposure of the above plants to such water, however, metal levels in the plants increased tremendously. The increased metal levels in plants severely damaged their physiological and biochemical processes. The contents of chlorophyll a, b and carotenoid were reduced by 63.2, 64.2, and 46.3%, respectively, in E. crassipes, 41, 57.4, and 57.8% in S. molesta, and 42, 62, and 61% in P. stratiotes. The accumulating metals also generated oxidative stress in plants, as evident from the increased superoxide dismutase and catalase activities and enhanced malondialdehyde content. The E. crassipes was the most potent in absorbing the metals from the CME-fed pond water, followed by S. molesta and P. stratiotes.     

Hemochromatosis gene variants in three different ethnic populations: effects of admixture for screening programs

Genetic testing for hemochromatosis may have important implications for diagnosis and screening of the disease. However, the relative importance of mutations in the gene for hereditary hemochromatosis, HFE, may vary among populations, when the mutant allele frequencies and their penetrance in a particular genetic and environmental background are taken into account. We present data on the allele and genotype frequencies and population structure of two HFE genetic variants in three different ethnic groups from a highly mixed urban population (S?o Paulo, Brazil). Allele frequencies for both the C282Y and H63D HFE mutations showed significant differences among the studied populations (for the C282Y mutation, Euro-Brazilian 3.7%, admixed 0.7%, Afro-Brazilian 0.5%; and for the H63D mutation, Euro-Brazilian 20.3%, admixed 13.0%, Afro-Brazilian 6.4). The data substantiate a European origin for these mutations. Furthermore, they provide a basis for a more rational strategic planning of population screening programs for the disease.     

The functional grazing response of a phytoplanktivorous fish Oreochromis mloticus to mixtures of toxic and non-toxicstrains of the cyanobacterium Microcystis aeruginosa

Small (10 g) tilapia ( Oreochromis niloticus ) were exposed to pure and mixed populations of toxic and non-toxic strains of the cyanobacterium Microcystis aeruginosa (100% toxic, 50% toxic, 25% toxic, 0% toxic) at two particle concentrations (1 × 10⁶ and 5 × 10^sparticles ml⁻¹). At both concentrations there was a progressive decrease in grazing rate as the percentage of toxic cells increased. Differences in opercular beat rates, and hence the volumes of water passed over the gills, were also recorded among treatments, opercular beat rates decreasing as the percentage of toxic cells increased. Although in all treatment groups with toxic cells present, the medium had detectable levels (>250 ng I⁻¹) of extracellular microcystin-LR toxin present, grazing was correlated with particle-bound rather than extracellular levels.     

A comparative study of gut microbiota profiles of earthworms fed in three different substrates

The gut microbiome of earthworms has a complex interdependence with the host. When the soil minerals pass through earthworm’s gut, they may affect the gut microbiota. To gain insight into the response of gut microbiota to the passed minerals, we fed earthworm (Eisenia fetida) on nutrient-poor soil and ore powder, and used high throughput sequencing to characterize the earthworm intestinal microbial community to find evidence for a core bacterial community of the E. fetida. The results showed that earthworms’ gut maintained a core microbiome that appeared in all samples. These core microbiota may play a significant role in a species’ environmental interactions. The composition of intestinal microbiomes varied with substrates. The earthworm guts from two nutrient-poor substrates had similar microbial communities and they were different from nutrient-rich substrate. Proteobacteria and Bacteroidetes were more abundant in the gut of earthworms kept on a nutrient-poor substrate such as ore powder or mineral soil than in the gut of earthworms kept in organic-rich compost soil; some of these microorganisms may help earthworms survive in nutrient-poor substrates.     

Long‐term effect of a tidal,hydroelectric propeller turbine on the populations of three anadromous fish species

Tidal hydroelectric power has been proposed as one potential solution for sustainable energy sources. The first tidal turbine in North America began continuous operation in the Annapolis River estuary (44 °45′N; 65° 29′W) in June, 1985. The machine is an axial‐flow, hydraulic‐lift propeller turbine, a type known to cause fish mortality. Anadromous populations of American shad Alosa sapidissima, striped bass Morone saxatilis and Atlantic sturgeon Acipenser oxyrinchus utilize the Annapolis River for spawning and other life history phases. After power generation commenced obvious turbine mortalities of these fishes began appearing downstream of the turbine. Assessments of the A. sapidissima adult spawning runs during 1981–1982 (pre‐operation) and 1989–1996 (operational) indicated significant changes in population characteristics after power generation began. Adult length, mass, age and per cent repeat spawners declined and total instantaneous mortality (Z) increased from 0.30 to 0.55. The pre‐turbine spawning runs had older fish with numerous adult cohorts whereas by 12 years after operation began runs consisted of younger fish with fewer adult cohorts. During 1972–1987 numerous studies indicated the Annapolis River had an important angling fishery for M. saxatilis, but detailed annual records kept by a fishing contest during 1983–1987 and an elite angler family during the period 1976–2008 demonstrated a rapid decline in the number of fish >4.0 kg after turbine operation began. Pre‐turbine catch by the angling family of fish >4.0 kg accounted for 84.1% of total catch, but declined significantly to 39.6% of total catch from 1986–1999, and to none from 2000–2008. The existence of an A. oxyrinchus stock in the Annapolis River was unknown before turbine operation, but during 1985–2017, 21 mortalities were recovered by chance seaward of the turbine. Mechanical strike and cavitation mortalities consisted of juveniles, mature males and gravid and spent females of ages 10 to 53 years found during June to October, the period when this anadromous species returns to its natal river to spawn. The results of the long‐term studies at Annapolis indicate managers should realize substantial risks exist for the fish resources of the world's oceans from deployment of instream propeller turbines.     

Quantifying stress responses induced by different handling methods in three species of fish

Although interest in fish welfare is growing, little research has addressed the welfare of laboratory or ornamental fish. Our aim here was to evaluate the effects of handling fish with a scoop, where the fish remained submerged in water, compared to handling with a net. We investigated the effect of the scoop vs. a dip-net in three different species: three-spined sticklebacks (Gasterosteus aculeatus), Panamanian bishops (Brachyraphis episcopi) and rainbow trout (Oncorhynchus mykiss) using a variety of assays. The results demonstrate that keeping fish within water in a scoop while transferring them between tanks can, but not always, decrease the negative effects of handling on stress responses.     

Analysis of translocations observed in three different populations. II. Robertsonian translocations

A sample of 229 Robertsonian translocations was classified into three groups according to the method of their ascertainment (Group I = couples with repeated abortions; Group II = karyotypically unbalanced probands; Group III = balanced translocation heterozygotes). Statistical analysis showed that the distributions of Robertsonian translocations differed significantly from random in all three groups. Additionally, the distributions were significantly different between couples with repeated abortions and karyotypically unbalanced probands and between unbalanced probands and balanced translocation heterozygotes.