Hematology of free-ranging, lactating northern fur seals, Callorhinus ursinus

Thirteen standard hematology values were determined for a healthy and growing population of free-ranging, lactating northern fur seals (Callorhinus ursinus) from Lovushki Island in the Kuril Islands of far-east Russia. Results are presented from 24 females sampled between June and August during the 3-yr period of 2006-08. Hematologic values have been made available for future comparisons with the declining population of northern fur seals on the Pribilof Islands, Alaska, and are compared with published values for other otariid species.     

Herbivore Effects on Ecosystem Process Rates in a Low-Productive System

Ecosystems - Mammalian herbivores shape the structure and function of many nutrient-limited or low-productive terrestrial ecosystems through modification of plant communities and plant–soil...     

Long-Term Experiments Reveal Strong Interactions Between Lemmings and Plants in the Fennoscandian Highland Tundra

Both the theory and the observations suggest that, there are strong links between herbivores and plants in terrestrial ecosystems; although, the effect of herbivores on plant community biomass is often attributed to variations in plant palatability. The existence of a strong link is commonly tested by constructing exclosures that exclude herbivores during a period of time. We here present data from two long-term (9 and 20 years, respectively) herbivore exclosure studies in lemming habitats on arctic tundra in northernmost Norway. The exclusion of all mammalian herbivores triggered strong increases in community level plant biomass and substantial changes in plant community composition. Palatable plants like graminoids and large bryophytes, as well as unpalatable plants like evergreen ericoids, deciduous shrubs, and lichens were all favored by excluding lemmings. These results reveal that a substantial increase in community biomass which occurs only when plant species capable of accumulating biomass are present, and palatability is a poor predictor of long-term responses of plants to excluding herbivores.     

Intraperitoneal implantation of life-long telemetry transmitters in otariids

Background

Pinnipeds, including many endangered and declining species, are inaccessible and difficult to monitor for extended periods using externally attached telemetry devices that are shed during the annual molt. Archival satellite transmitters were implanted intraperitoneally into four rehabilitated California sea lions (Zalophus californianus) and 15 wild juvenile Steller sea lions (Eumetopias jubatus) to determine the viability of this surgical technique for the deployment of long-term telemetry devices in otariids. The life history transmitters record information throughout the life of the host and transmit data to orbiting satellites after extrusion following death of the host.

Results

Surgeries were performed under isoflurane anesthesia and single (n = 4) or dual (n = 15) transmitters were inserted into the ventrocaudal abdominal cavity via an 8.5 to 12 cm incision along the ventral midline between the umbilicus and pubic symphysis or preputial opening. Surgeries lasted 90 minutes (SD = 8) for the 19 sea lions. All animals recovered well and were released into the wild after extended monitoring periods from 27 to 69 days at two captive animal facilities. Minimum post-implant survival was determined via post-release tracking using externally attached satellite transmitters or via opportunistic re-sighting for mean durations of 73.7 days (SE = 9.0, Z. californianus) and 223.6 days (SE = 71.5, E. jubatus).

Conclusion

The low morbidity and zero mortality encountered during captive observation and post-release tracking periods confirm the viability of this surgical technique for the implantation of long-term telemetry devices in otariids.

     

Quantitation of Semlike Forest virus RNAs in infected cells using 32-P equilibrium labelling.

In vitro cultured BHK and HeLa cells were labelled for several cell division cycles with 32-P-phosphate until they were equilibrated with radiophosphorus. After infection with Semliki forest virus (or mock-infection) these cells were analyzed for viral and ribosomal RNA by sucrose gradient centrifugation. From their radioactivities the mass of each RNA species was calculated. It was found that the BHK and HeLa cells contained on average 11.0 plus or minus 3.1 pg and 6.3 plus or minus 1.9 pg of ribosomal RNA (28 S + 18 S) respectively per cell. At the end of the viral growth cycle, i.e. at 8 h post infection the average mass of viral genome produced per cell was 1.0 -1.9 pg and 0.3 - 0.5 pg in BHK and HeLa cells respectively, of which only 1/10 to 1/20 was released as mature virus particles. The amount of the second major virus specific messenger, the 26 S RNA, was estimated from its ratio to the viral genome after labelling with 3-H-uridine in the presence of actinomycin D. These two viral RNAs were found to be present in roughly equimolar amounts.     

Defoliation increases carbon limitation in ectomycorrhizal symbiosis of <Emphasis Type="Italic">Betula pubescens</Emphasis>

Boreal forest trees are highly dependent on root-colonizing mycorrhizal fungi. Since the maintenance of mycorrhizal symbiosis implies a significant carbon cost for the host plant, the loss of photosynthetic leaf area due to herbivory is expected to reduce the host investment in mycorrhizae. We tested this hypothesis in a common garden experiment by exposing ectomycorrhizal white birch (Betula pubescens Ehrh.) seedlings to simulated insect defoliation of 50 or 100% intensity during either the previous or the current summer or repeatedly during both seasons before harvest. The shoot and root growth of the seedlings were distinctly reduced by both 100% defoliation and repeated 50% defoliation, and they were more strongly affected by previous-year than current-year defoliation. The root to shoot ratio significantly decreased after 100% defoliation, indicating reduced proportional allocation to the roots. Ergosterol concentration (i.e. fungal biomass) in the fine roots decreased by 100% defoliation conducted either in the year of harvest or in both years. No such decrease occurred following the 100% defoliation conducted in the previous year, indicating the importance of current photosynthates for fungal symbionts. The trend was similar in the colonization percentage of thick-mantled mycorrhizae in the roots, the most marked decline occurring in the repeatedly defoliated seedlings. The present results thus support the prediction that the plant investment in ectomycorrhizae may decline as a response to foliage loss. Moreover, the colonization percentage of thick-mantled mycorrhizae correlated positively with the ratio of leaf to heterotrophic plant biomass in the defoliated birch seedlings, but not in the control ones. This tends to indicate a stronger carbon limitation of ectomycorrhizal colonization in defoliated seedlings.     

The abundance of nahAc genes correlates with the 14C-naphthalene mineralization potential in petroleum hydrocarbon-contaminated oxic soil layers

In this study, we evaluated whether the abundance of the functional gene nahAc reflects aerobic naphthalene degradation potential in subsurface and surface samples taken from three petroleum hydrocarbon contaminated sites in southern Finland. The type of the contamination at the sites varied from lightweight diesel oil to high molecular weight residuals of crude oil. Samples were collected from both oxic and anoxic soil layers. The naphthalene dioxygenase gene nahAc was quantified using a replicate limiting dilution-polymerase chain reaction (RLD-PCR) method with a degenerate primer pair. In the non-contaminated samples nahAc genes were not detected. In the petroleum hydrocarbon-contaminated oxic soil samples nahAc gene abundance [range 3 x 10(1)-9 x 10(4) copies (g dry wt soil)(-1)] was correlated (Kendall non-parametric correlation r2=0.459, p<0.01) with the aerobic 14C-naphthalene mineralization potential (range 1 x 10(-5)-0.1 d(-1)) measured in microcosms at in situ temperatures (8 degrees C for subsurface and 20 degrees C for surface soil samples). In these samples nahAc gene abundance was also correlated with total microbial cell counts (r2=0.471, p<0.01), respiration rate (r2=0.401, p<0.01) and organic matter content (r2=0.341, p<0.05). NahAc genes were amplified from anoxic soil layers indicating that, although involved in aerobic biodegradation of naphthalene, these genes or related sequences were also present in the anoxic subsurface. In the samples taken from the anoxic layers, the aerobic 14C-naphthalene mineralization rates were not correlated with nahAc gene abundance. In conclusion, current sequence information provides the basis for a robust tool to estimate the naphthalene degradation potential at oxic zones of different petroleum hydrocarbon-contaminated sites undergoing in situ bioremediation.     

Electron microscopy of tick-borne fever agent in bovine and ovine phagocytizing leukocytes

Tuomi, Jaakko (University of Helsinki, Helsinki, Finland), and C.-H. von Bonsdorff. Electron microscopy of tick-borne fever agent in bovine and ovine phagocytizing leukocytes. J. Bacteriol. 92:1478-1492. 1966.-Two strains of tick-borne fever agent, one more virulent to cattle and the other more virulent to sheep, were studied in thin sections of leukocyte concentrates of an affected calf and sheep, respectively. The calf was partially immune from previous infections. To obtain leukocyte concentrate, erythrocytes were lysed by ammonium chloride solution. Glutaraldehyde fixation and osmium tetroxide postfixation were used. Agent particles were detected in neutrophil and eosinophil granulocytes (occasionally also in monocytes) inside cytoplasmic vacuoles. The preparation from the sheep revealed that the tick-borne fever agent has a life cycle; it appeared as large particles, intermediate forms, and small particles. In the preparation from the calf, only large particles were observed, probably as a result of partial immunity. Large particles had a cell wall, plasma membrane, cytoplasm with ribosome-like granules, and nucleoid. They were often elongated, bearing closer resemblance to rickettsiae than to psittacosis-lymphogranuloma-trachoma (PLT) agents. The arrangement of large particles in vacuoles was variable and provided an explanation for the different forms of light microscopic tick-borne fever bodies. The intermediate forms and small particles resembled those of PLT organisms. Release of particles occurred by rupture of inclusions. In the calf also extrusion of whole inclusions was observed. This phenomenon was thought to reflect increased resistance of the cells. The large particle was considered to be the usual infective form of the agent. A middle-ground position of the agent between the genus Rickettsia and the PLT group is suggested.     

Predator–rodent–plant interactions along a coast–inland gradient in Fennoscandian tundra

Spatial variation in the strength of trophic cascades in arctic tundra has been related to flows of subsidies across ecosystem boundaries. Here, we ask whether the input of marine subsidies in tundra systems would cause spatial variation in the strength of rodent–plant interactions between coastal areas, where predators have access to marine‐derived resources, and non‐subsidized inland areas of northern Fennoscandia. We present a detailed evaluation of predator–rodent–vegetation interactions along a coast‐inland gradient, during the 2011 rodent outbreak and the two following decline years, by using direct assessments of rodent impacts and tracing of marine‐derived nutrients in the food web. Our results revealed that the main rodent predator during summer, the long‐tailed jaeger Stercorarius longicaudus, did not benefit from marine resources while breeding (relative dietary proportion in chicks’ diet = 0–3%). Contrary to this pattern, parasitic jaegers S. parasiticus, bred exclusively near the coast and preyed effectively on both marine resources (41% of chicks’ diet) and rodents (12%). Mammalian predators also showed a higher activity during winter near the coast. Despite overall higher predator numbers, no evidence was found for lower rodent population growth rates during the three monitoring summers and for weaker rodent grazing impacts in the coastal area. Instead, we documented pronounced damages caused by lemmings and voles on bryophytes and vascular plants, especially dwarf shrubs (e.g. Vaccinum myrtillus) all along the coast–inland gradient. Taken together, our results did not support the hypothesis that marine subsidies would trigger a trophic cascade in coastal tundra areas of northern Fennoscandia during a major rodent outbreak, probably due to a relatively low diversity of marine‐subsidized predators in the region. Comparative observational and experimental studies at large spatial scales in various arctic regions are absolutely necessary for a better understanding of factors causing regional variations in the functioning of arctic food webs.