Seed dispersal effectiveness increases with body size in New Zealand alpine scree weta (Deinacrida connectens)

Weta are giant, flightless orthopterans that are endemic to New Zealand. Although they are known to consume fleshy fruits and disperse seeds after gut passage, which is unusual among insects, their effectiveness as seed dispersal mutualists is debated. We conducted a series of laboratory experiments on alpine scree weta (Deinacrida connectens) and mountain snowberries (Gaultheria depressa) to investigate how fruit consumption rates, the proportion of ingested seeds dispersed intact and weta movement patterns vary with weta body sizes. On average weta dispersed 252 snowberry seeds nightly and travelled at a rate of 4 m min^?1. However, seed dispersal effectiveness varied over three orders of magnitude and was strongly associated with body sizes. Smaller weta consumed few snowberry seeds and acted primarily as seed predators. On the other hand, the largest weta consumed and dispersed thousands of seeds each night and appear to be capable of transporting seeds over large distances. Overall results indicate that scree weta shift from being weakly interacting seed predators to strongly interacting, effective seed dispersers as they increase in size.     

Significance of cold-season respiration and photosynthesis in a subarctic heath ecosystem in Northern Sweden

While substantial cold-season respiration has been documented in most arctic and alpine ecosystems in recent years, the significance of cold-season photosynthesis in these biomes is still believed to be small. In a mesic, subartic heath during both the cold and warm season, we measured in situ ecosystem respiration and photosynthesis with a chamber technique at ambient conditions and at artificially increased frequency of freeze–thaw (FT) cycles during fall and spring. We fitted the measured ecosystem exchange rates to respiration and photosynthesis models with R²-values ranging from 0.81 to 0.85. As expected, estimated cold-season (October, November, April and May) respiration was significant and accounted for at least 22% of the annual respiratory CO₂ flux. More surprisingly, estimated photosynthesis during this period accounted for up to 19% of the annual gross CO₂ uptake, suggesting that cold-season photosynthesis partly balanced the cold-season respiratory carbon losses and can be significant for the annual cycle of carbon. Still, during the full year the ecosystem was a significant net source of 120 ± 12 g C m⁻² to the atmosphere. Neither respiration nor photosynthetic rates were much affected by the extra FT cycles, although the mean rate of net ecosystem loss decreased slightly, but significantly, in May. The results suggest only a small response of net carbon fluxes to increased frequency of FT cycles in this ecosystem.     

Morphological and molecular investigation of polymorphism and cryptic species in tanaid crustaceans: implications for tanaid systematics and biodiversity estimates

A combination of traditional taxonomic procedures and molecular techniques has provided new insight into the problems of cryptic species and sexual and ontogenetic polymorphism in the Tanaidacea. Using polymerase chain reaction and DNA markers, three cryptic species of Paratanais were identified. PCR primers were used to amplify the divergent internal transcribed spacers (ITS) of these species. Restriction digestion of the amplified rDNA generated species specific DNA banding. Male and five female stages of Paratanais maleticus sp. nov. and two other new species, P. malign us and P. perturbatius , are described. Morphological variation, both sexual and ontogenetic, was found in several generic characters of Paratanais and required the diagnosis to be modified. The identification of three undescribed cryptic species from a single microhabitat in a well studied, shallow water and easily accessible locality, demonstrate that the biodiversity of tanaid crustacean is significantly underestimated.     

Immune response of rainbow trout (Oncorhynchus mykiss) to antigenic preparations fromVibrio anguillarumserogroup O1

The humoral and cellular immune responses of rainbow trout were investigated following injection with formalin-killedVibrio anguillarumin Freund's incomplete adjuvant (FIA) in terms of reactivity towards different antigen preparations of the bacterium. Vaccinated fish were compared with control fish that had been injected only with FIA. The antigen preparations used for the comparative studies were formalin-killed bacteria, extracellular products (ECP), outer membrane proteins (OMP) and cytoplasmic membrane proteins (CMP). Humoral antibody as measured by ELISA was detected with all antigen preparations. As evaluated by ELISPOT and by proliferation assays, leucocytes isolated from vaccinated fish reacted most strongly with the OMP preparation. This observation suggests the existence of undefined potent antigenic components among these proteins. In proliferation assays, the tested antigen preparations contained components that were mitogenic to cell cultures from unvaccinated fish. However, in terms of antibodies measured by ELISA and ELISPOT techniques, only vaccinated fish reacted with theV. anguillarumpreparations.     

Is Blepharisma hyalinum Truly Unpigmented?1

ABSTRACT. To answer whether Blepharisma hyalinum is truly unpigmented, the organism must be established in culture as pointed out by Giese in 1973. Accordingly, the present study deals with B. hyalinum kept in culture since its isolation in 1975. The organism still remains colorless after growth in the dark; however, it contains cortical granules resembling pigment granules in colored species. A comparative study was therefore undertaken of B. hyalinum and B. steini; both species have a compact macronucleus, though of different shape. Crude pigment was extracted with acetone from organisms grown in the dark for three weeks and the maxima were measured by absorption. Purified pigment was obtained from TLC-plate preparations and the absorption maxima were measured after removal of lipids with chloroform. No maxima characteristic of blepharismin were found in extracts of B. hyalinum, but these were present in extracts of B. steini. Electron microscopy of the cortical region revealed membrane-bound granules in both species; these granules differed in content but not in their capacity to extrude. In B. hyalinum all granules had a homogenous electron-dense substructure; in B. steini the granules had a net-like granulated substructure of varying electron density. This difference corresponds to that published on “pigment” granules in albino and pigmented strains of B. undulans. Our conclusions are that B. hyalinum is unpigmented (and a valid separate species) and that the cortical granules may serve other functions than that of storing blepharismin.     

History,rather than contemporary processes,determines variation in macroinvertebrate diversity in artesian springs: the expansion hypothesis

1. The relative importance of contemporary and historical processes is a fundamental question in understanding patterns of biodiversity. We tested the hypothesis that species‐sorting into different habitats (limnocrenes, rheocrenes, helocrenes), rather than history, would account for the greatest variation in macroinvertebrate diversity in desert artesian springs of The Bonneville Basin, U.S.A. These springs were isolated at the valley scale c. 9000 years ago by aridity and high salinity. Thus, the valley scale will account for the greatest variation in community composition if history and dispersal limitation are important, whereas niche‐based sorting processes will be most important if habitat accounts for the greatest variation in community composition. 2. We identified 302 taxa from 280 sites and used a partial redundancy analysis, additive partitioning and classification strength (CS) to partition the variability in diversity among the springs. The valley scale accounted for more variation in community composition in limnocrene habitats (32.5%) than all other spatial and environmental variables combined. Valleys also accounted for 58% (additive partitioning) and 83% (CS) of the regional variation in diversity in analyses that included all three habitat types. That is, the average community similarity was 25% across the region, but increased to 41% within valleys. By contrast, habitat filtering did not account for significant variation in community composition in any of the analyses. Our study is one of the few suggesting the over‐riding importance of neutral processes in determining patterns of diversity (history and dispersal limitation). 3. The ‘expansion’ hypothesis suggests that the youthful age of a region, combined with slow dispersal by a fauna dominated by generalists, will maximise the imprint of history. These communities appear to exist in a pre‐equilibrial state, where the maximum carrying capacity has not been reached and niche space is plentiful. With time, we predict that local richness will increase while β‐diversity decreases as species expand their distribution across the region. Consequently, the importance of niche‐based processes may increase with time as the imprint of history fades.     

On the energetics of the photosyntheses in green sulfur bacteria

The quantum efficiency of photosynthesis by the green sulfur bacterium, Chlorobium thiosulfatophilum, has been determined in systems in which thiosulfate, tetrathionate, and molecular hydrogen served as electron donors. It was found that about 10 ± 1 quanta are used for the assimilation of 1 molecule of CO₂, and that the quantum number is independent of the nature of the electron donor. These results are considered as support for the view that also in the bacterial photosyntheses the primary photochemical reaction consists in the photolysis of H₂O, and that the chemical energy released during the oxidation of the electron donor is not utilized for CO₂ assimilation. Hence the photosynthetic processes of the green sulfur bacteria are thermodynamically less efficient than is green plant photosynthesis.     

Population genetic structure of North Atlantic, Mediterranean Sea and Sea of Cortez fin whales, Balaenoptera physalus (Linnaeus 1758): analysis of mitochondrial and nuclear loci

Samples were collected from 407 fin whales, Balaenoptera physalus , at four North Atlantic and one Mediterranean Sea summer feeding area as well as the Sea of Cortez in the Pacific Ocean. For each sample, the sex, the sequence of the first 288 nucleotides of the mitochondrial (mt) control region and the genotype at six microsatellite loci were determined. A significant degree of divergence was detected at all nuclear and mt loci between North Atlantic/Mediterranean Sea and the Sea of Cortez. However, the divergence time estimated from the mt sequences was substantially lower than the time elapsed since the rise of the Panama Isthmus, suggesting occasional gene flow between the North Pacific and North Atlantic ocean after the separation of the two oceans. Within the North Atlantic and Mediterranean Sea, significant levels of heterogeneity were observed in the mtDNA between the Mediterranean Sea, the eastern (Spain) and the western (the Gulf of Maine and the Gulf of St Lawrence) North Atlantic. Samples collected off West Greenland and Iceland could not be unequivocally assigned to either of the two areas. The homogeneity tests performed using the nuclear data revealed significant levels of divergence only between the Mediterranean Sea and the Gulf of St Lawrence or West Greenland. In conclusion, our results suggest the existence of several recently diverged populations in the North Atlantic and Mediterranean Sea, possibly with some limited gene flow between adjacent populations, a population structure which is consistent with earlier population models proposed by Kellogg, Ingebrigtsen, and Sergeant.     

Information parasitism in foraging Bar-tailed Godwits Limosa lapponica

Foraging behaviour of sympatric Bar-tailed Godwits Limosa lapponica and Whimbrels Numenius phaeopus was studied in the period prior to egg-laying. Godwit females preferred wet bogs, while godwit males and Whimbrels foraged on dry palsas in the bogs. Habitat overlap between godwit males and Whimbrels was larger than intersexual overlap in the godwits. Observations of scanning behaviour of foraging godwits showed that the vigilance level of males was not affected by the presence or absence of their mates. Female vigilance levels, however, dropped significantly when females fed near their mate, and—in the absence of the mate—near Whimbrels. While female godwits benefited from associating with Whimbrels, males seemed to avoid close proximity to this species. Whimbrels chased godwit males more often than females, presumably because they used the same foraging habitats.