Lissarca notorcadensis (Bivalvia: Philobryidae) living on Notocidaris sp. (Echinoidea: Cidaridae): Population dynamics in limited space

Summary Population dynamics of the epizoic bivalve Lissarca notorcadensis living on spines of cidaroid sea urchins in the Weddell Sea were investigated. Total production (somatic & gonad) of the suspension feeding bivalve ranged between 16.5 and 487.4 mg AFDM y^–1 per sea urchin. Annual sedimentation rates are not sufficient to maintain the production of the Lissarca sub-populations carried by the sea urchins, and resuspension of organic matter is most likely to be an important food source. The ratio of the number of freshly settled juveniles to the number of embryos brooded is between 0.054 and 0.207 and seems negatively related to the biomass already present, indicating intraspecific competition for space. Interspecific competition for space is caused by the strong preference of L. notorcadensis as well as other epizoa (colonial anthozoans and bryozoans) for the spines located on the aboral hemispere of the sea urchins.AWI Publication No. 572     

Structure and biodiversity of megabenthos in the Weddell and Lazarev Seas (Antarctica): ecological role of physical parameters and biological interactions

A community analysis of the mega-zooepibenthos at water depths between 99 and 1243 m was carried out for the Weddell and Lazarev Seas (47°W 77°S–12°E 70°S). A total of 144,531 specimens were counted and 313 taxa were identified from 3,768 photographs at 55 stations, which represented approximately 3,304 m² of seafloor. The stations were classified into six groups according to their inventory of taxa although they represented rather a gradient from a rich and diverse suspension feeder assemblage to a poorer assemblage. In the latter, the proportion of deposit feeders was higher than in the former. A statistical comparison between biological and physical data showed that the faunistic pattern could best be explained by a combination of water depth and a geographical gradient. A positive correlation between the abundance of large sponges and the number of all other taxa was found. Received: 16 September 1997 / Accepted: 11 April 1998     

A simple but highly effective approach to evaluate the prognostic performance of gene expression signatures

Background

Highly parallel analysis of gene expression has recently been used to identify gene sets or ‘signatures’ to improve patient diagnosis and risk stratification. Once a signature is generated, traditional statistical testing is used to evaluate its prognostic performance. However, due to the dimensionality of microarrays, this can lead to false interpretation of these signatures.

Principal Findings

A method was developed to test batches of a user-specified number of randomly chosen signatures in patient microarray datasets. The percentage of random generated signatures yielding prognostic value was assessed using ROC analysis by calculating the area under the curve (AUC) in six public available cancer patient microarray datasets. We found that a signature consisting of randomly selected genes has an average 10% chance of reaching significance when assessed in a single dataset, but can range from 1% to ∼40% depending on the dataset in question. Increasing the number of validation datasets markedly reduces this number.

Conclusions

We have shown that the use of an arbitrary cut-off value for evaluation of signature significance is not suitable for this type of research, but should be defined for each dataset separately. Our method can be used to establish and evaluate signature performance of any derived gene signature in a dataset by comparing its performance to thousands of randomly generated signatures. It will be of most interest for cases where few data are available and testing in multiple datasets is limited.     

Internalization of paramagnetic phosphatidylserine-containing liposomes by macrophages

ABSTRACT: BACKGROUND: Inflammation plays an important role in many pathologies, including cardiovascular diseases, neurological conditions and oncology, and is considered an important predictor for disease progression and outcome. In vivo imaging of inflammatory cells will improve diagnosis and provide a read-out for therapy efficacy. Paramagnetic phosphatidylserine (PS)-containing liposomes were developed for magnetic resonance imaging (MRI) and confocal microscopy imaging of macrophages. These nanoparticles also provide a platform to combine imaging with targeted drug delivery. RESULTS: Incorporation of PS into liposomes did not affect liposomal size and morphology up to 12 mol% of PS. Liposomes containing 6 mol% of PS showed the highest uptake by murine macrophages, while only minor uptake was observed in endothelial cells. Uptake of liposomes containing 6 mol% of PS was dependent on the presence of Ca2+ and Mg2+. Furthermore, these 6 mol% PS-containing liposomes were mainly internalized into macrophages, whereas liposomes without PS only bound to the macrophage cell membrane. CONCLUSIONS: Paramagnetic liposomes containing 6 mol% of PS for MR imaging of macrophages have been developed. In vitro these liposomes showed specific internalization by macrophages. Therefore, these liposomes might be suitable for in vivo visualization of macrophage content and for (visualization of) targeted drug delivery to inflammatory cells.     

Stone crabs close to the Antarctic Continent: Lithodes murrayi Henderson, 1888 (Crustacea; Decapoda; Anomura) off Peter I Island (68°51′S, 90°51′W)

Live reptant decapod crustaceans have never been collected on the Antarctic continental shelf, although shrimps occur locally in large quantities. Therefore, the collection of four male individuals of the anomuran decapod Lithodes murrayi off Peter I Island, close to the Antarctic Continent, between 180 and 260 m water depth in February 1994 is of particular relevance for further studies on the origin and adaptation of Antarctic decapods. Another five specimens were observed in situ by a remotely operated vehicle at the same location.     

Gut microbiota composition is associated with environmental landscape in honey bees

There is growing recognition that the gut microbial community regulates a wide variety of important functions in its animal hosts, including host health. However, the complex interactions between gut microbes and environment are still unclear. Honey bees are ecologically and economically important pollinators that host a core gut microbial community that is thought to be constant across populations. Here, we examined whether the composition of the gut microbial community of honey bees is affected by the environmental landscape the bees are exposed to. We placed honey bee colonies reared under identical conditions in two main landscape types for 6 weeks: either oilseed rape farmland or agricultural farmland distant to fields of flowering oilseed rape. The gut bacterial communities of adult bees from the colonies were then characterized and compared based on amplicon sequencing of the 16S rRNA gene. While previous studies have delineated a characteristic core set of bacteria inhabiting the honey bee gut, our results suggest that the broad environment that bees are exposed to has some influence on the relative abundance of some members of that microbial community. This includes known dominant taxa thought to have functions in nutrition and health. Our results provide evidence for an influence of landscape exposure on honey bee microbial community and highlight the potential effect of exposure to different environmental parameters, such as forage type and neonicotinoid pesticides, on key honey bee gut bacteria. This work emphasizes the complexity of the relationship between the host, its gut bacteria, and the environment and identifies target microbial taxa for functional analyses.     

Seed dormancy release and germination characteristics of <i>Corispermum lehmannianum</i> Bunge,an endemic species in the Gurbantunggut desert of China

Seed dormancy release and germination of Corispermum lehmannianum Bunge were tested using various treatments: temperature, cold stratification, gibberelins (GA3), dry storage and sand burial. Results showed that temperature and light did not affect the germination of fresh seeds, cold stratification and GA3 could improve seed germination, whereas dry storage and sand burial did not. The germination percentage was highest at 35/20 °C after the cold stratification and GA3 treatments. Corispermum lehmannianum seeds were classified as non-deep, Type-2, physiological dormancy (PD), whose seed dormancy could be released by cold stratification and GA3.     

Enemy at the Gates: Interaction-Specific Stomatal Responses to Pathogenic Challenge

Stomata regulate gas exchange and their closure in response to pathogens may, in some cases, contribute to resistance. However, in the cereal mildew and rust systems, stomatal closure follows establishment of compatible infections. In incompatible systems, expression of major (R) gene controlled hypersensitive responses (HR), causes drastic, permanent stomatal dysfunction: stomata become locked open following powdery mildew attack and locked shut following rust attack. Thus, stomatal locking can be a hitherto unsuspected negative consequence of R gene resistance that carries a physiological cost affecting plant performance.Key Words: stomata, rust, mildew, hypersensitive response, stomatal lock-up