Linking intronic polymorphism on the CHD1‐Z gene with fitness correlates in Black‐tailed Godwits Limosa l. limosa

We show that variation in an intronic length polymorphism in the CHD1‐Z gene in Black‐tailed Godwits Limosa l. limosa is associated with fitness correlates. This is the second example of the CHDZ‐1 gene being correlated with fitness, a previous study having established that Moorhens Gallinula chloropus carrying the rare Z* allele have reduced survival. In Godwits, however, carriers of the Z* allele (374 bp) fared better than those with the more frequent Z allele (378 bp) with respect to body mass, plumage ornamentation, reproductive parameters and habitat quality. The Z* allele was found in 14% of 251 adult birds from nature reserves, but was absent from 33 birds breeding in intensively managed agricultural lands. Males and females with the Z* allele had less extensive breeding plumage, and females had a higher body mass, bred earlier and had larger eggs. There were no significant differences in annual survival between birds with and without the Z* allele. DNA isolated from museum skins demonstrated that this polymorphism was present at low frequency in 1929. We speculate that strong asymmetrical overdominance may explain the low frequency of the Z* allele and that genetic linkage to causal genes might be an explanation for the phenotypic correlations. Our findings suggest a degree of cryptic genetic population structuring in the Dutch Godwit population.     

Effet de la farnesylacetone sur les syntheses proteiques de l'ovaire chez le crabe Carcinus maenas

Summary

We have analysed in vitro the effect of farnesylacetone, a substance produced by the androgenic gland of Crustacea, in a concentration of 20 ng/ml, on the protein synthesis in the ovary of Carcinus maenas. In winter, the farneslyacetone seems to be ineffective; the incorporation of labelled precursor per mass unity is then related to the weight of the sample. In summer, an activation of protein synthesis can be observed. These results do not depend on ovary maturation and concern all the proteins of the gonad.     

Further evidence for cortical control over replication of the macronucleus and basal bodies in Stentor

This paper presents further evidence that the cortex controls macronuclear replication and basal body production during the cell cycle of Stentor. At the onset of cell division, basal body production occurs on the ventral side of the cell to form an oral primordium; this structure develops slowly into the oral apparatus destined for the posterior daughter cell. Meanwhile, a series of morphological changes in the macronucleus (coalescence, elongation, nodulation) doubles the number of nodes in preparation for division. When a cell undergoing oral development is grafted to a morphostatic cell of equal size, oral development is usually induced in the morphostatic component and the two members of the graft complex eventually become synchronized with respect to macronuclear morphology. However, primordium induction and nuclear synchronization usually do not occur when the 2 members of the graft complex are separated by cortical discontinuities which heal gradually, even though the graft components demonstrably share a common endoplasm throughout the experiment. These results suggest that the cell surface may control the replication of organelles such as the macronucleus and basal bodies which are normally kept “in step” with the cell cycle in such a way that they are not lost or reproduced too frequently.     

Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

1. Predation‐exclusion experiments have highlighted that top‐down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. 2. We conducted 1‐year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. 3. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant‐excluded than in control trees, whereas only dermapterans were more abundant in bird‐excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. 4. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator–prey system.