Search Results - (Author, Cooperation:P. A. Jansen)

2012-06-16

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

*Plagiarism ; *Scientific Misconduct

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Brown trout (Salmo trutta) from anadromous River Lierelva, resident Lake Tunhovd, and resident Nordmarka stocks were exposed to Gyrodactylus salaris-infected salmon parr. The brown trout were fed pellets before the experiments, except for one group of the Nordmarka stock which was starved for 19 days before the experiments. The mean number of parasites declined directly and rapidly post infection for all groups of trout. There were no pronounced differences in resistance between the anadromous and the resident stocks. G. salaris infections tended to persist longer on starved than on fed trout of the Nordmarka stock. The maximum parasite persistence on trout was 50 days, and as parasite numbers increased on some fish parasite reproduction must have occurred on those trout. However, the limited susceptibility and marked innate resistance of trout to G. salaris establishment, development and reproduction, suggest parasite metapopulations will not survive on this species. Nevertheless, trout may still play a role in the dispersal of G. salaris within and between rivers.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Biomass size distributions (BSDs) can be useful tools to (1) summarize complex information about fish community structure in a condensed graphical form, facilitating the characterization of freshwater fish communities, (2) compare the position of fish communities along environmental gradients and (3) elucidate major trophic interactions in freshwater fish communities. Biomass size distributions are presented by taxonomic and trophic group, for a selection of fish communities from 35 Scandinavian and eight Dutch lakes. They were used for the analysis of taxonomic and trophic shifts in the fish communities along a large environmental gradient, with productivity (expressed as total phosphorus concentration, TP) as its most important component. Regression analysis of fish community variables (such as proportion of cyprinids, or biomass of benthivores) were consistent with the semi-quantitative conclusions drawn from BSDs, regarding taxonomic and trophic shifts with changes in TP in both Scandinavian and Dutch lakes, especially an increase in the amount and size of benthivorous fishes with increasing TP-levels. In addition, differences in mortality and growth rates were shown to partly explain differences in BSDs. Biomass size distributions thus provide an integrative tool for qualitative and quantitative comparisons among fish communities.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

The susceptibility and resistance of hatchery-reared salmon parr, native to the rivers Neva (U.S.S.R. Baltic Sea), Alta (northern Norway) and Lone (western Norway) (both eastern Atlantic Ocean), to Gyrodactylus salaris from Norway, was examined. The level of resistance to the parasite was assessed from counts, made on anaesthetized salmon, ofthe numbers of G. salaris after an initial experimental exposure (2 weeks) to G. salaris-infected salmon. Three experiments, all in water at c. 12° C, were carried out: (1) 50 Alta and 50 Neva salmon, initial mean parasite intensity c. 12; (2) 50 Lone and 50 Neva salmon, initial mean parasite intensity c. 60; (3) 10 Lone and 10 Neva salmon individually isolated, initial intensity one gravid G. salaris. In both the Norwegian salmon stocks, the G. salaris infrapopulations steadily increased during the experimental period of 5 weeks, in contrast to a prominent decline in the Neva salmon stock, after, respectively: (Exp. 1) week 3, average peak intensity 32.6; (Exp. 2) week 2, average peak intensity 58.7; and (Exp. 3) week 3, average peak intensity 6.3. The hatchery-reared Baltic Neva stock demonstrated both an innate and an acquired resistance towards G. salaris, in contrast to the highly susceptible, Norwegian Alta and Lone salmon stocks.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

The host specificity of Gyrodaclylus Solaris is examined experimentally with respect to its ability to infect the brook trout, Salvelinus fontinalis. The parasite readily attached to and reproduced on parr of this host and infections grew for c. 20 days from first monitoring (c. 30 days from first infection) before declining. Parasites could persist on this host for up to 70 days before finally disappearing. The pattern of infection resembled that seen in many other gyrodactylid species on their normal hosts, and suggested the action of a host response, In this respect infections of G. salaris on parr of S. fontinalis, anadromous Salvelinus alpinus, Oncorhynchus mykiss, Thymallus thymallus and Baltic Salmo salar follow a normal pattern, while infections of Norwegian S. salar are unusual in a continued unchecked growth, until the host dies, under pooled laboratory conditions.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

An experimental epidemiological approach was chosen to study the survival and infection dynamics of Gyrodactylus salaris on juvenile rainbow trout, Oncorhynchus mykiss, in the laboratory. A marked heterogeneity in the host stock was apparent. The rainbow trout could be divided into three groups on the basis of parasite survival and infection pattern on individually isolated fish: (1) hosts receptive to initial parasite attachment, but unreceptive to parasite establishment and reproduction; (2) hosts moderately susceptible to parasite establishment and reproduction, but which, after a period of restricted parasite population growth, responded, recovered and eliminated the parasites; and (3) hosts very susceptible to parasite infection and reproduction, but which, after a period of significant parasite population growth, responded, recovered and eliminated the parasites. These different patterns are considered to reflect genetic differences between host individuals. Parasite aggregation was also shown to be an important factor in the outcome of the host-parasite association. The parasites were finally eliminated on the individually isolated hosts, but not on hosts maintained in batches and so host population size and immigration of fresh. previously unexposed, hosts appeared to be important for growth and maintenance of the parasite population. The parasite was not found to cause host mortality. Rainbow trout was a suitable host for G. salaris, capable of transmitting the parasite to new localities as a consequence of stocking programmes or migratory behaviour.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Prey capture rate (number of prey s−1) and the mode of feeding of Arctic charr Salvelinus alpinus were studied by performing foraging experiments with two sizes (1·1 and 1·8 mm) of Daphnia longispina prey. Arctic charr were particulate feeders at all densities tested. Adjusted for the effect of prey density, the capture rate showed a hump-shaped relationship with Arctic charr size for both sizes of D. longispina. Estimated attack rates (a) also tended to show a hump-shaped relationship with fish size. The estimated size-scaling exponent of the attack rate function, however, was relatively small, implying small changes in attack rate over fish sizes. Simultaneous estimations of a and handling time were used in combination with published data on fish metabolism and dry mass rations of prey to estimate maintenance resource density of prey as a function of Arctic charr mass. Maintenance resource densities increased monotonically with Arctic charr size, and rapidly as optimum fish size relative to attack rate on prey was passed.

Electronic Resource

1095-8649

Blackwell Publishing Journal Backfiles 1879-2005

Biology

The ability of Gyrodactylus salaris, an important pathogen of the Atlantic salmon Salmo salar, in Norway, to infect anadromous and resident stocks of the Arctic charr, Salvelinus alpinus, has been examined in the laboratory. Resident charr (Korssjoen stock) exposed to heavily infected salmon, were considered innately resistant as they lost their infections within 21 days when individually isolated. Isolated anadromous harr (Hammerfest stock) remained infected for up to 150 days, although most infections disappeared within 30–50 days. In many cases the parasite population grew initially, but growth was limited after 20–30 days and infections subsequently disappeared. At the same time, shoals of 50 anadromous charr, swimming in the tanks containing the individually isolated fish in floating cages, remained infected for up to 280 days. Charr isolated from these shoals after 115 days and subsequently monitored individually lost their infections within 30 days, although the parasite persisted within the shoals for a further 75–135 days. This suggests that G. salaris, persisted on shoaling charr despite an immune response which led to the elimination of parasites from isolated hosts. The Hammerfest stock of anadromous charr supports G. salaris, in the laboratory, and the extended period of survival on this host suggests that charr may be important in the epidemiology of G. salaris, in northern Norway.

Electronic Resource

1600-0633

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Abstract – Production of cannibalistic Arctic char (Salvelinus alpinus (L.)) and their prey conspecifics were estimated in an allopatric population, situated in an alpine ultraoligotrophic lake in central Norway. Estimates of population abundance were obtained by mark recapture and successive removal experiments. Assuming stable age distribution, we estimated mean yearly biomass (±95% CL) of char in sampled size groups vulnerable to predation (60 to 150 mm) to 7.93 (5.11–14.30) kg · ha−1. Similarly, mean yearly biomass (±95% CL) of cannibalistic char (〉 250 mm) was estimated to 0.62 (0.50–1.06) kg · ha−1. Annual production (±95% CL) of char in length groups 60 to 150 mm was estimated to be 4.31 (2.74–8.03) kg · ha−1 · year−1, and production (±95% CL) of cannibalistic char to 0.19 (0.15–0.33) kg · ha−1 · year−1. Depending on the food conversion factor (set to vary from 0.1 to 0.4), the cannibalistic char removed from 10% to 40% of the production of char in sampled size-classes vulnerable to predation yearly. The overall ecological efficiency in energy transfer between the prey and predator population was 4.4%./〉

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The laser resonance Raman spectrum of bathorhodopsin differs from both rhodopsin and isorhodopsin by having additional peak at 1,539, 920, 877 and 856cm?1. The 1,539 cm?1 absorption is consistent with both the N?H ene?amine structure derived from a primary amine and a protonated Schiff base ...

Electronic Resource

1573-739X

Antineoplastic agents ; Cells, cultured ; Doxorubicin ; Drug resistance ; Methotrexate

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electronic Resource