Estimating primate densities using home range and line transect methods: A comparative test with the black colobus monkeyColobus satanas

The line transect method is one of the main methods used to estimate primate densities. Several protocols have been proposed to analyze the data recorded under this method but none of them have been widely accepted since there is a considerable controversy about their respective accuracy. In this study, densities of the black colobus monkeyColobus satanas calculated using eight different protocols were compared with the actual density given by the home range method. Rates of polyspecific associations were also compared. The two most accurate estimates of group density (under- or overestimation <10%) were yielded by the protocol that used the maximum transect-to-animal distance and by that of using a fixed distance of 100 m. These protocols, however, underestimated individual density because counts performed from transects underestimated by 23% the average group size. The six other protocols overestimated group density by 20–195%. Factors that could explain these overestimation were discussed. Because histogram of sighting frequency showed several classes of distances with no records and because groups have been detected as far as 160 m, we suggested that the uneven topography of the study site increased the variability of the sighting distances. Combined with a relatively low number of sightings (n=23), this did not allow to identify a sharp detection distance. Rates of polyspecific association found with the two methods were similar. We recommend to investigate the influence of the topography for bias in density estimates when using the line transect method.     

Spatial expectation of food location in an ant on basis of previous food locations (Hymenoptera,Formicidae)

We examined if workers of the ant species Myrmica ruginodis would be able to localize a food source on the basis of its previous locations. To this end we progressively relocated food to predefined positions, both linearly, i.e., farther or nearer the nest entrance, and circularly, i.e., to the left or to the right of the nest entrance. After removal of food from one site and prior to the subsequent relocalization of the food to the next site, we counted the number of ants present at the different possible food locations. We found that the ants initially came to the site from where the food had just been removed, but following two or three relocations of food, they foraged around the following, expected food location in statistically significant numbers. The workers thus appeared to be able to spatially anticipate where food would be on the basis of its previous localizations. Such ability—hitherto unreported in ants—requires a knowledge of the environment around the nest, a long-term visual memory, memorization of the location of some food locations, knowledge of the pattern of food supply, some degree of providence, presentation of some anticipative behavior, and estimation of their orientation of movement and distances walked. These seven capabilities have been separately observed in previous studies on Myrmica species. Here, we report that the ant M. ruginodis also has the ability to learn a relation between previous food sites and a next one.     

Diterpenes from the leaves of Croton zambesicus

Two new trachylobane- and one isopimarane-type diterpenoids: ent-18-hydroxy-trachyloban-3-one; ent-trachyloban-3-one; isopimara-7,15-dien-3beta-ol, were isolated from the leaves of Croton zambesicus, together with trans-phytol, beta-sitosterol, alpha-amyrin and stigmasterol. The structures were determined by extensive NMR techniques and X-ray analysis. The cytotoxicity of these compounds has been evaluated on cancer and non-cancer cell-lines.     

APC/C-mediated degradation of dsRNA-binding protein 4 (DRB4) involved in RNA silencing

Background

Selective protein degradation via the ubiquitin-26S proteasome is a major mechanism underlying DNA replication and cell division in all Eukaryotes. In particular, the APC/C (Anaphase Promoting Complex or Cyclosome) is a master ubiquitin protein ligase (E3) that targets regulatory proteins for degradation allowing sister chromatid separation and exit from mitosis. Interestingly, recent work also indicates that the APC/C remains active in differentiated animal and plant cells. However, its role in post-mitotic cells remains elusive and only a few substrates have been characterized.

Methodology/Principal Findings

In order to identify novel APC/C substrates, we performed a yeast two-hybrid screen using as the bait Arabidopsis APC10/DOC1, one core subunit of the APC/C, which is required for substrate recruitment. This screen identified DRB4, a double-stranded RNA binding protein involved in the biogenesis of different classes of small RNA (sRNA). This protein interaction was further confirmed in vitro and in plant cells. Moreover, APC10 interacts with DRB4 through the second dsRNA binding motif (dsRBD2) of DRB4, which is also required for its homodimerization and binding to its Dicer partner DCL4. We further showed that DRB4 protein accumulates when the proteasome is inactivated and, most importantly, we found that DRB4 stability depends on APC/C activity. Hence, depletion of Arabidopsis APC/C activity by RNAi leads to a strong accumulation of endogenous DRB4, far beyond its normal level of accumulation. However, we could not detect any defects in sRNA production in lines where DRB4 was overexpressed.

Conclusions/Significance

Our work identified a first plant substrate of the APC/C, which is not a regulator of the cell cycle. Though we cannot exclude that APC/C-dependent degradation of DRB4 has some regulatory roles under specific growth conditions, our work rather points to a housekeeping function of APC/C in maintaining precise cellular-protein concentrations and homeostasis of DRB4.     

Identification of a new transposon Tn5403 in aKlebsiella pneumoniae strain isolated from a polluted aquatic environment

AKlebsiella pneumoniae strain having mobilization helper potential has been isolated from the river Rhine. Analysis of the transconjugants resulting from the mobilization of nonconjugative pBR-type plasmids and RSF1010 derivatives showed that the transfer-helper capacity of theK. pneumoniae strain is related to the presence of a Tn3-like transposable element, Tn5403. This element has been identified and localized in a plasmid.