Influence of temperature on muscle-fibre development in larvae of the herringClupea harengus

The development of swimming (myotomal) muscles was studied in herring larvae (Clupea harengus L.) caught in the Firth of Clyde, Scotland, in spring 1990 and reared at either 5, 10 or 15°C. Two muscle-fibre types can be distinguished in the myotomes of herring larvae using ultrastructural criteria. A single layer of small-diameter muscle fibres, packed with mitochondria, is present beneath the entire surface of the skin (superficial muscle fibres). The remaining bulk of the muscle is composed of larger diameter fibres (inner muscle fibres) containing significantly more myofibrils than the superficial fibres. In 1 d-old larvae, the number of inner muscle fibres in myotomes immediately posterior to the yolk-sac was 311±41 at 15°C, 257±22 at 10°C and 187±22 at 5°C (mean±SD,n=6). The average diameter of inner muscle fibres increased with decreasing temperature, so that the total cross-sectional area of muscle was similar at each temperature. After 6 to 7 d, the number of muscle fibres had significantly increased at 15°C (383±25), but not at 10°C (281±32) or 5°C (192±17). In contrast, the average cross-sectional area of inner muscle fibres had increased by 19% at 15°C, 34% at 10°C, and 26% at 5°C. Temperature also influenced the relative proportions and spatial distributions of muscle-fibre organelles. For example, in 1 d-old larvae, the fraction of muscle-fibre volume (volume density) occupied by mitochondria in the superficial fibres was significantly higher at 15°C (46.0%) than at either 5°C (37.6%) or 10°C (38.8%). In the inner muscle fibres, the volume density of mitochondria was 26.1% at 15°C, 20.5% at 10°C and 15.9% at 5°C, whereas the volume density of myofibrils was similar at the three temperatures (33 to 38%). Typically, inner muscle fibres from 10°C larvae, but not from 5 or 15°C larvae contained a large central mitochondrion.     

‘Fishing’ for Alternatives to Mountaintop Mining in Southern West Virginia

Mountaintop removal mining (MTR) is a major industry in southern West Virginia with many detrimental effects for small to mid-sized streams, and interest in alternative, sustainable industries is on the rise. As a first step in a larger effort to assess the value of sport fisheries in southern West Virginia, we estimate the potential abundances of two popular sport fishes—smallmouth bass (Micropterus dolomieu) and brook trout (Salvelinus fontinalis)—in the Coal River Basin (CRB). A self-thinning model that incorporates net primary production and terrestrial insect subsidies is first used to predict potential densities of adult (age 1+) smallmouth bass and brook trout. Predicted densities (fish ha^?1) are then multiplied by the surface area of the CRB stream network (ha) to estimate regional abundance. Median predicted abundances of bass and trout are 38 806 and 118 094 fish (total abundances with the CRB), respectively. However, when streams that intersect permitted MTR areas in the CRB are removed from the dataset, predicted abundances of bass and trout decrease by ~12–14 %. We conclude that significant potential exists in the CRB to capitalize on sport fisheries, but MTR may be undermining this potential.     

Temperature and developmental plasticity during embryogenesis in the Atlantic cod<Emphasis Type="Italic"> Gadus morhua</Emphasis> L.

Atlantic cod (Gadus morhua L.) embryos were reared at 4 °C, 7 °C, and 10 °C, and the relative timing of developmental events was characterized, with particular reference to myotomal muscle. Embryos started to feed at an apparently equivalent stage of development, so comparisons were made between temperature groups on the basis of percentage of time to first feeding and somite stage. No differences were found in the time of hatching or timing of appearance of the otic placode, unpaired median fin fold, gut lumen, otic vesicle, lens of the eye, otoliths, first muscular contractions, swim bladder, and hindgut, or in the rate of development of somites, myotubes, myofibrils, and acetylcholinesterase activity over the temperature range studied. In contrast, closure of the blastopore occurred late with respect to segmentation at higher temperatures, at the 3-somite, 10-somite, and 12-somite stages at 4 °C, 7 °C, and 10 °C respectively. Muscle cellularity was also markedly altered in the 10 °C group relative to the 4 °C and 7 °C groups. Larvae reared at 10 °C had significantly more (+14%) deep white fibers at hatch (P <0.001), whereas numbers of superficial red fibers remained unchanged. It is suggested that differences in muscle cellularity might be related to changes in the relative timing of epiboly, through differential proliferation of presomitic myogenic cells and/or their relative exposure to inductive signals.     

Evidence that lipid can be digested by the dumpling squid Euprymna tasmanica, but is not stored in the digestive gland

The aims of this study were to assess quantitatively the enzymatic ability of squid to digest lipids and the ability of the digestive gland to accumulate lipid classes associated with storage. This was achieved through two manipulative experiments using the dumpling squid, Euprymna tasmanica. Firstly, we measured lipase activity and determined the presence and location of lipid vacuoles within the digestive gland; secondly we identified and quantified lipid classes in the digestive gland. Given the levels of lipase activity, we provided evidence for the first time that a squid species is capable of digesting lipid at levels comparable to invertebrates known to use dietary lipid. A poor relationship between feeding activity and lipase secretion suggests that enzyme production is continuous. The second experiment found no evidence that lipid was stored in the digestive gland; most of the lipid present in the gland was either structural or a dietary by-product. The implication of these findings is that for this species lipid is most probably being immediately digested and used for growth and reproduction rather than being stored in the digestive gland. We consider that the role and storage of lipid is likely to vary among different cephalopod species, but not predictably as function of their lifestyle. Therefore, potential locations for lipid storage, other than the digestive gland, need to be considered and using changes in the relative size of the digestive gland as a measure of condition needs to be interpreted with care.     

Effects of prochloraz and malathion on the red-legged partridge: a semi-natural field study

A semi-natural field study was carried out to assess the likelihood of a potentiation of toxicity between the ergosterol biosynthesis inhibiting (EBI) fungicide, prochloraz, and the organophosphorus (OP) insecticide, malathion, in the red-legged partridge (Alectoris rufa). Groups of partridges kept in four large grassland enclosures were exposed to either prochloraz-treated or control wheat for 7 days after which two of the enclosures were sprayed with malathion whilst the remaining two were sham-sprayed. Cytochrome P-450, aldrin epoxidase and 7-ethoxyresorufin-O-deethylase (EROD) activities were found to be significantly higher in the group exposed to prochloraz alone compared to controls, suggesting that induction of the hepatic microsomal monooxygenase system had occurred by ingestion of prochloraz-treated wheat. However, the level of induction produced was not sufficient to cause a potentiation of malathion toxicity. There was evidence for induction of several forms of P-450 recognised by antibodies raised against 1A1, 2C6 and 4A1 in the prochloraz-exposed partridges.     

What have we learned from highly time-resolved measurements during EPA's Supersites Program and related studies?

A wide range of new and exciting highly time-resolved instruments were deployed during the U.S. Environmental Protection Agency (EPA) Supersite program and related studies that occurred during the same time period. These measurements elucidated the temporal variation of a suite of gas-phase species, particle physical properties, and size-resolved particulate chemical composition. Because the temporal resolution was so high, concentration and size distribution changes as short as 1 min or less were discerned. Often data from multiple instruments were correlated with each other and with meteorological measurements, and these correlations enabled conclusions to be drawn about the photochemical activity of the atmosphere, the location of point sources, and even the emissions characteristics of these sources. For instance, rapid changes in particulate matter (PM) concentration were due to meteorological conditions, emissions, and plume excursions that led to increases in nitrate, sulfate, and organic carbon concentrations. This paper summarizes the conclusions that have been reached, to date, using these new, highly time-resolved instruments, and demonstrates their promise for future studies.     

Source characterization and identification by real-time single particle mass spectrometry

A Real-Time Single Particle Mass Spectrometer, RSMS-3, was deployed to Wilmington, Delaware to study regional and local contributions to fine and ultra-fine urban particulate matter (PM). Approximately two-thirds of PM₁ consisted of internally mixed secondary aerosol. The remaining one-third was externally mixed including biomass burning (13%), fossil fuel combustion (7%) and various industrial sources (13%). In this last group, particle classes containing specific combinations of transition and/or heavy metals gave wind-rose plots consistent with specific point sources. For example, particles containing V and Ni were detected from different wind directions than those containing V and Fe. Samples from two industrial emission stacks, a steel manufacturing facility 10 km away and a coal-fired electrical power generation facility 5 km away, were analyzed and compared to the ambient data set. In each case, a direct correlation was found: a Pb–Zn–K–Na class for the steel manufacturing facility and an Fe–La/Ce class for the power generation facility. The ambient particle classes showed additional small signals from secondary components indicating atmospheric processing. Ambient particle classes containing only a subset of these elements, such as Zn only, Fe only and Pb–K only, were nonspecific, that is, the wind-rose plots were more diffuse and the particles could not be mapped to individual sources. The merits of stack sampling as an aid to interpreting single particle data sets are discussed.     

Comparing differential tolerance of native and non-indigenous marine species to metal pollution using novel assay techniques

Recent research suggests anthropogenic disturbance may disproportionately advantage non-indigenous species (NIS), aiding their establishment within impacted environments. This study used novel laboratory- and field-based toxicity testing to determine whether non-indigenous and native bryozoans (common within marine epibenthic communities worldwide) displayed differential tolerance to the common marine pollutant copper (Cu). In laboratory assays on adult colonies, NIS showed remarkable tolerance to Cu, with strong post-exposure recovery and growth. In contrast, native species displayed negative growth and reduced feeding efficiency across most exposure levels. Field transplant experiments supported laboratory findings, with NIS growing faster under Cu conditions. In field-based larval assays, NIS showed strong recruitment and growth in the presence of Cu relative to the native species. We suggest that strong selective pressures exerted by the toxic antifouling paints used on transport vectors (vessels), combined with metal contamination in estuarine environments, may result in metal tolerant NIS advantaged by anthropogenically modified selection regimes.     

Evaluation of commercial odor control agents for suppressing Escherichia coli in swine manure slurry

Ten commercially available manure odor control agents were evaluated in bench-scale laboratory microcosms for their ability to inhibit or kill Escherichia coli, a commonly used indicator of fecal pollution and a potential pathogen. At manufacturer recommended rates, none of the agents reduced viable populations of E. coli in pure cultures or in swine manure slurry. However, at rates 10-fold higher than those recommended by the manufacturer, EnviroPur rapidly reduced viable populations of E. coli. Accelerated death of E. coli was observed at temperatures as low as 4 degrees C. Chemical analysis of EnviroPur indicated that it contains alkylphenol polyethoxylates, common industrial surfactants. These results suggest that at manufacturer-recommended rates, the odor-controlling agents would not be effective at suppressing E. coli in stored swine manure slurry.