Ascorbate-2-sulfate as a dietary vitamin C source for Atlantic salmon (Salmo salar): 2. Effects of dietary levels and immunization on the metabolism of trace elements

Atlantic salmon fingerlings were fed a vitamin C deficient diet for four months. The fish were then provided a dry, practical fishmeal based diet supplemented with 0, 500 or 5000 mg vitamin C/kg as L-ascorbic acid or equivalent amounts of ascorbate-2-sulfate. After six weeks on these diets ten fish in each group were injected with a soluble antigen (NIP₁₁-LPH). Six weeks thereafter blood, liver, kidney, spleen and vertebrae were examined for trace elements. The livers were also analysed for metallothionein. The vitamin C deficient fish were anemic despite the significantly elevated iron concentrations in the liver. Vitamin C had no positive effect in lowering tissue levels of cadmium. The highest level of dietary vitamin C given as ascorbic acid reduced the liver selenium concentrations. In response to antigen injection, the fish in all groups showed increased levels of hepatic metallothionein, copper, zinc and cadmium, while hepatic selenium and iron levels were less affected. The elemental composition in other organs was affected by the antigen injection to a minor extent.     

Browsing of sallow (Salix caprea L.) and rowan (Sorbus aucuparia L.) in the context of life history strategies: a literature review

Sallow (Salix caprea L.) and rowan (Sorbus aucuparia L.) constitute small proportions of the deciduous tree volume in Scandinavia, but are highly preferred winter forage for moose and red deer, which occur at historically high densities. Thus, a possible decline of these tree species has been indicated. Against this background, we have reviewed the life histories of relevance for browsing, as well as the basic biology and genetics of sallow and rowan. The species show similarities with respect to short lifespan, small size and sympodial growth pattern, which are risk factors in a browsing context. They also have high juvenile growth rate, important for growing quickly out of reach of browsers. Sallow depends strongly on disturbance for establishment and is more demanding with respect to soil and light conditions than rowan, possibly important for the substantially lower abundance of sallow on the Norwegian Forest Inventory plots. Similarly, the relative recruitment of small size classes of sallow is less than for rowan. Although recruitment is reported to be hampered in wintering areas with high moose or red deer densities, the inventory data, however, dating only back to 1994, do not suggest a general decrease in any of the species. Sallow and rowan saplings show low mortality in moose and deer dominated areas and the species can be characterised as rather resilient to browsing. Of more concern is that browsing can constrain the development of mature rowan and sallow trees locally, with possible consequences for associated epiphytic biodiversity.     

Effects of genotype and environment on total anti-oxidant capacity and the content of sugars and acids in strawberries (Fragaria × ananassa Duch.)

Summary

Total anti-oxidant capacity (TAC) and the contents of mono- and disaccharides, and organic acids were determined in strawberry fruit from ten genotypes sampled from eight experimental sites in Norway in 2002 and 2003. The difference between genotypes was significant for all recorded traits, and it appeared possible to select for all traits in breeding programmes. On average, the Norwegian bred cultivar ‘Carmen’ had a TAC of 30.07 mmol kg^–1 fresh weight (FW), compared to 23.16 mmol kg^–1 FW in the standard cultivar ‘Korona’. TAC was negatively correlated with fruit size, rainfall and leaf surface humidity, but was positively correlated with the minimum temperature on the day prior to sampling. Mono- and di-saccharide contents were negatively correlated with both minimum and maximum temperatures, and with wind velocity. It was confirmed that the sugars:organic acids ratio was inversely related to the maximum temperature on the day before harvest, which supports anecdotal claims that strawberries grown in northern areas have, on average, better flavour.     

Transport of alpha-tocopherol in Atlantic salmon (Salmo salar) during vitellogenesis

The transport of α-tocopherol was studied during vitellogenesis in Atlantic salmon that were fed diets with two levels of α-tocopherol. α-Tocopherol levels were measured in the flesh, liver, ovary and serum, and in the serum the α-tocopherol levels in the very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL) and very high density lipoprotein (VHDL or vitellogenin) were also measured. Atlantic salmon store α-tocopherol mainly in their flesh because the muscle mass comprises 50% or more of live weight. During vitellogenesis the α-tocopherol content declined to about 10% of the level prior to maturation. The relative range of level of α-tocopherol in the lipoproteins was: HDL> LDL> VLDL> VHDL, irrespective of dietary levels of α-tocopherol. From the recent knowledge on lipid transport during vitellogenesis and the present data, we hypothesize that α-tocopherol is transported from peripheral tissues to liver by HDL and further transported from liver to ovary by LDL. Vitellogenin appears to play a minor role in the transportation of vitamin E to the ovary.     

An immunohistochemical study of retinol-binding protein (RBP) in livers of free-living polar bears (Ursus maritimus) from east Greenland.

From 1999 to 2002 samples from 114 free-ranging polar bears (Ursus maritimus) were collected in the municipality of Scoresby Sound, East Greenland, to detect levels of organochlorines and potential histopathologic changes. Livers of 16 female polar bears from this group were evaluated histologically and analyzed for hepatic retinol-binding protein by immunohistochemistry. Retinol-binding protein is the main transport protein for retinol, an important vitamin A metabolite in the polar bear. Only mild pathologic changes were noted on histologic evaluation of the livers. Small lymphocytic or lymphohistiocytic infiltrates were present in all the livers. Small lipid granulomas, mild periportal fibrosis, and bile duct proliferation were found in several cases. Immunohistochemistry for retinol-binding protein of hepatic tissue from free-ranging polar bears showed no distinct difference in staining intensity by a number of criteria: age, season (fasting and nonfasting), or lactation status. The staining was diffuse to finely stippled in the cytoplasm and showed very little variation among the animals. Because of the lack of macroscopic changes and the absence of severe histologic liver lesions, these polar bears were assumed to be healthy. The diffuse cytoplasmic retinol-binding protein staining in hepatocytes of free-ranging polar bears varies markedly from the prominent granular, less intense staining of captive polar bears investigated previously.     

Variation in DVM behaviour of juvenile and adult pearlside (Maurolicus muelleri) linked to feeding strategies and related predation risk

In the Norwegian fjord Masfjorden, different developmental stages of the mesopelagic planktivore Maurolicus muelleri form vertically separate sound scattering layers (SSLs) and in late autumn display different diel vertical migration (DVM) behaviour. Post‐larvae and juvenile fish perform normal crepuscular DVM, whereas the large majority of adults remain at depth throughout the diel period. In this study we examined the stomach contents of juvenile and adult fish caught at different times and depths during a 24‐h period in autumn. The different DVM behaviour of these two SSLs in addition to a shallow layer believed to be composed of post‐larvae is explained with a model for visual foraging in aquatic environments that uses gradients in vertical light intensity and copepod density and size as input variables. Field data revealed that vertically migrating juveniles distributed at a higher ambient light intensity and on average consumed 25 times more copepods than non‐migrating adult fish. The model showed that juveniles experienced a 15 times higher prey encounter rate and a higher level of predation risk than non‐migrating adults, and that the energetic benefits for post larvae and juveniles from prolonged feeding in a nearly constant and brighter environment outweigh the associated predation risk. The model also suggests that the visual detection range of piscivore predators is relatively more limited by the turbid surface water than that of their prey, which provide the post‐larva and juvenile life‐stages of M. muelleri a window of reduced visual predation near the surface.     

How do university-industry collaborations benefit innovation? Direct and indirect outcomes of different collaboration types

This paper explores the extent to which firms perceive to benefit from university-industry collaborations in their innovation processes, building on survey data from 232 Norwegian firms. We find that firms experience not only direct innovation benefits from collaborations, but also indirect benefits in the form of closer proximity to universities, which can in turn improve future collaboration. We compare the reported outputs from various types of collaboration, finding that firms engaging mainly in research-oriented interactions more often report that collaborations result in innovation than those engaging in education-oriented or more informal collaborations. However, education-oriented and informal collaborations are equally important for building cognitive, organizational, institutional and social proximities between firms and universities.     

Dietary plasticity of Arctic charr (Salvelinus alpinus) facilitates coexistence with competitively superior European whitefish (Coregonus lavaretus)

Abstract – Habitat use and diet of Arctic charr (Salvelinus alpinus) coexisting with European whitefish (Coregonus lavaretus) and grayling (Thymallus thymallus) were studied in one deep and two relatively shallow subarctic lakes in northern Norway. Stomach content and stable isotope analyses revealed clear and temporally stable resource partitioning between the species in all three lakes. Arctic charr had a wide and flexible trophic niche and was the only piscivorous species. In contrast, whitefish and grayling had remarkably stable planktivorous and benthivorous niches, respectively. In the deepest lake, Arctic charr together with grayling mainly utilised littoral benthos, while piscivory was more prevalent in Arctic charr in the two shallower lakes. In one of the shallow lakes, whitefish was apparently relegated to the inferior profundal niche because of dominance of the littoral by grayling. Our results suggest that Arctic charr may not necessarily need an extensive profundal zone as a refuge, but can coexist with whitefish if a third competing fish species like grayling occurs in the littoral habitat or if profitable small prey fish are available. The study demonstrates that strong dietary plasticity of Arctic charr is instrumental in the observed coexistence with the commonly competitively superior whitefish.