Phylogenetic analysis of the SSU rRNA gene from the piscine diplomonad Spironucleus torosus (Diplomonadida: Hexamitinae)

Previous studies have recorded Spironucleus torosus Poynton et Morrison, 1990 from several species of gadoid fishes, including the only freshwater gadoid, the burbot Lota lota (L.). Two morphologically different isolates of S. torosus have been described (elongate and pyriform). Both have been found in saltwater, while only the elongate has been found in freshwater. To address the conspecificity of the two morphs of S. torosus, and to identify the source of S. torosus in burbot in Norway, we have sequenced the small subunit ribosomal RNA (SSU rRNA) gene from 43 isolates of S. torosus from six species of gadoid fishes sampled at 15 localities in Norway, Sweden and the Baltic Sea. Phylogenetic analyses of the SSU rRNA gene sequence data recovered two major clades, one containing mainly isolates from burbot, while the other contained isolates from marine gadoid fishes only. The genetic distance (based on 25 nucleotide substitutions in 789 base pairs) separating the two assemblages was not large enough to consider the two groups separate species. Spironucleus torosus isolated from burbot displayed limited genetic variation in the small subunit ribosomal RNA (SSU rRNA) gene along the post-Pleistocene migration route of its host. The present study is the first report of S. torosus in tusk Brosme brosme (Ascanius), whiting Merlangius merlangus (L.), and fourbeard rockling Enchelyopus cimbrius (L.).     

New evidence on a cold case: trophic transmission, distribution and host-specificity in Hedruris spinigera (Nematoda: Hedruridae)

The life cycle of Hedruris spinigera Baylis, 1931 (Nematoda: Hedruridae) is determined here with the first formal identification of the parasite's intermediate host: the crustacean amphipod Paracorophium excavatum Thomson. Adult H. spinigera are redescribed from specimens collected from the stomach of fishes, Retropinna retropinna (Richardson) and Aldrichettaforsteri (Valenciennes), from Lake Waihola, New Zealand. Immature adults of the parasite collected from intermediate hosts (P. excavatum) are also described for the first time. The prevalence, abundance and intensity of infection of H. spinigera in several fish species are quantified along with the occurrence of P. excavatum, the parasite's intermediate host, in fish stomach contents. Although H. spinigera's transmission mode (trophic transmission) and fish diet potentially expose all fish species to infection, some level of host specificity must exist as parasite prevalence, abundance and intensity of infection vary greatly between potential definitive host species. We suggest here that the anatomy of the fish digestive tract and especially that of the stomach plays an important role in host suitability for H. spinigera. While P. excavatum is the only intermediate host in Lake Waihola, H. spinigera was found in six different fish species: Aldrichetta forsteri, Galaxias maculatus (Jenyns), Retropinna retropinna, Rhombosolea retiaria Hutton, Perca fluviatilis Linnaeus and Salmo trutta Linnaeus; although typical hedrurid attachment and mating positions were observed only in R. retropinna and A. forsteri. The limited distribution of H. spinigera is most likely due to that of its different host species (intermediate and definitive), all inhabitants of coastal fresh and brackish waters.     

Hepatic intranuclear glycogen inclusions in western barred bandicoots (Perameles bougainville).

The western barred bandicoot, Perameles bougainville, is an endangered Australian marsupial species. Routine histology of liver samples collected at necropsy from 19 of 20 (95%) western barred bandicoots revealed the sporadic to common occurrence of abnormal hepatocyte nuclei characterized by margination of chromatin and concomitant central pallor. Some abnormal hepatocyte nuclei were mildly to markedly enlarged and irregularly shaped. Periodic acid-Schiff reagent stained 131 of 142 (92%) of these abnormal hepatocyte nuclei. Positive staining was completely eliminated by diastase pretreatment. Transmission electron microscopy revealed that abnormal hepatocyte nuclei with marginated chromatin did not contain viral particles. Rather, glycogen beta-particles and alpha-rosettes were identified within some abnormal hepatocyte nuclei. Glycogen intranuclear inclusions were an incidental finding in western barred bandicoot hepatocytes.     

Land-cover and structural changes in a western Norwegian cultural landscape since 1865, based on an old cadastral map and a field survey

Many studies of land-cover and structural changes in cultural landscapes have used historical maps as a source for information about past land-cover. All transformations of historical maps onto modern coordinate systems are however burdened with difficulties when it comes to accuracy. We show that a detailed land survey of the present landscape may enable transformation of an old cadastral map directly onto the present terrain with very high accuracy. The detailed resulting map enabled us to locate remnants of semi-natural grasslands and man-made structures with continuity from 1865 and to test hypotheses about relationships between landscape changes and landscape characteristics. The main land-cover change 1865–2002 was decrease of arable fields, and addition of three new land-cover classes: horticultural, orchard and abandoned areas. Of the 330 man-made structures present in 1865, only 58 remained in 2002, while 63 new structures had been built after 1865. We found that semi-natural grasslands with continuity since 1865 were situated on ground with significantly lower production capacity than mean 1865 production capacity. The man-made structures with continuity since 1865 were also associated with areas with significantly lower production capacity than the 1865 mean, situated in significantly steeper terrain but not further from the hamlet. Our study illustrates the potential of digitised and accurately transformed historical cadastral maps combined with detailed field surveys for analysis of land-cover and structural changes in the cultural landscape.     

Minimum requirement of vitamin E for Atlantic salmon, Salmo salar L., at first feeding

The minimum requirement of vitamin E for Atlantic salmon, Salmo salar L., at first feeding was found to be 60 mg dl-α-tocopheryl acetate per kg dry diet. The dry diet contained 5.6% polyunsaturated fatty acids, which is similar to that used in practical diets at first feeding. Preliminary results indicate that the optimal dietary vitamin E level is 120 mg dl-α-tocopheryl acetate per kg dry diet, or more. Further research is necessary to confirm this hypothesis.     

A comparison of retinol, retinal and retinyl ester concentrations in larvae of Atlantic halibut (Hippoglossus hippoglossus L.) fed Artemia or zooplankton

Atlantic halibut (Hippoglossus hippoglossus L.) larvae were fed enriched Artemia or zooplankton in duplicate tanks from 0 to 60 days after first‐feeding. Both diets and the larvae were analysed for vitamin A (VA) in order to confirm earlier findings, in which Artemia fed larvae had lower levels of VA compared with larvae fed zooplankton. Furthermore, we wanted to investigate the composition of the retinoids in the larvae. The results showed that Artemia and zooplankton contains low levels of VA, probably too low to sustain the assumed requirement. Nevertheless, larvae fed Artemia had the same level of retinal and retinol as larvae fed zooplankton. We found a significant lower level of retinyl esters in larvae fed Artemia. The total VA level was lower in larvae fed Artemia only at the end of the feeding trial after the onset of metamorphosis. Our conclusion is that feeding Artemia to Atlantic halibut larvae is not likely to cause VA deficiency.     

Thirty years of change and the future of Alaskan fisheries: Shifts in fishing participation and diversification in response to environmental,regulatory and economic pressures

Heterogeneity in human responses and decision‐making can contribute to the resilience of social–ecological systems in the face of environmental, political and economic pressures. In fishery systems worldwide, the ability of harvesters to maintain a diverse portfolio of fishing strategies is important for building adaptive capacity. We used a case‐study approach to examine the complexity of factors that inhibit or promote diversification in fisheries of Alaska, one of the major fishing regions of the world. Through a combination of harvest records and literature review, we explored shifts in participation and portfolio diversity in Alaskan fisheries over three decades. The four case‐studies examined the responses of fishers, fleets and communities to multiple, intersecting pressures, including biological declines, market and price dynamics, fishery privatization and the 1989 Exxon Valdez oil spill. These cases illustrate how stressors acting at multiple scales can encourage or constrain opportunities for diversification, and that these opportunities may be spread inequitably across participants. Overall, we found evidence for reduced participation and increasing specialization in Alaskan commercial fisheries. While numerous factors explain these trends, policies like individual quota systems and the increasing cost of entry into fisheries are forcing consolidation at local to regional scales. A portfolio approach to managing fisheries that reduces barriers to diversification and includes broad representation of resource users and communities in management may help to maintain opportunity and choice for fishers.