Floristic inventory and diversity assessment of a lowland African Montane Rainforest at Korup,Cameroon and implications for conservation

Twenty modified‐Whittaker plots were stratified at different sampling locations from February to May of 2008 in the central zone of Korup National Park, Cameroon. Our interest was to assess floristic diversity and investigate their relationship with environmental variables. Diversity profiles and rank abundance–curves were used for diversity analysis while canonical correspondence analysis and species–response curves were used to investigate the relationships between the response and explanatory variables. Of the 66 families identified, the Rubiaceae (999 species) were the most abundant. The Sterculiaceae (basal area = 10.482 m² ha^?1) were the dominant family, while the co‐dominant families included the Ebenaceae (basal area = 9.092 m² ha^?1) and the Euphorbiaceae (basal area = 8.168 m² ha^?1). Soil variables explained 54.3% of total variation in family distribution. Canonical axes were related to different environmental gradients: axis1 was related to increasing canopy cover (r = 0.6951); axis 2, increasing Magnesium (r = 0.8465) and effective cation exchange capacity (r = 0.5899); axis 3, increasing effective cation exchange capacity (r = 0.5536); while axis 4, increasing Phosphorus concentration (r = 0.5232). Our results demonstrate the advantage which diversity profiles have over single or combination of indices, and the importance of using a combination of methodologies in diversity analysis.     

Specific roles for the Ccr4-Not complex subunits in expression of the genome

In this work we used micro-array experiments to determine the role of each nonessential subunit of the conserved Ccr4-Not complex in the control of gene expression in the yeast Saccharomyces cerevisiae. The study was performed with cells growing exponentially in high glucose and with cells grown to glucose depletion. Specific patterns of gene deregulation were observed upon deletion of any given subunit, revealing the specificity of each subunit''s function. Consistently, the purification of the Ccr4-Not complex through Caf40p by tandem affinity purification from wild-type cells or cells lacking individual subunits of the Ccr4-Not complex revealed that each subunit had a particular impact on complex integrity. Furthermore, the micro-arrays revealed that the role of each subunit was specific to the growth conditions. From the study of only two different growth conditions, revealing an impact of the Ccr4-Not complex on more than 85% of all studied genes, we can infer that the Ccr4-Not complex is important for expression of most of the yeast genome.     

Interspecific variations in the morphology and ultrastructure of the rhabdoms of oplophorid shrimps

Interspecific variations in rhabdom structure between various oplophorid shrimps are described and the differences are related to the light environment at different depths within the mesopelagic zone. The ultrastructure of the distal rhabdom in these species is described for the first time. Quantitative measurements show that the proportion of the rhabdom layer occupied by the distal rhabdom varies from 3.5-25% in the dorsoventral plane of the eye of Systellaspis debilis. The distal rhabdom occupies less than 1% of the rhabdoms in the eye of Acanthephyra pelagica, where it can only be seen by using the electron microscope. It is suggested that the rhabdoms of those species that remain within the photic zone (such as S. debilis) are adapted to maximize contrast, whereas in those whose depth ranges extend into the aphotic zone (such as A. pelagica) they are adapted for maximum sensitivity.     

A Golgi-electron-microscopical study of the structure and development of the lamina ganglionaris of the locust optic lobe

Summary The gross structure as well as the neuronal and non-neuronal components of the lamina ganglionaris of the locust Schistocerca gregaria are described on the basis of light- and electron-microscopical preparations of Golgj (selective silver) and ordinary histological preparations. The array of optic cartridges within the lamina neuropile — their order and arrangement — and the composition of the cartridges are described. There are six types of monopolar neurons: three whose branches reach to other cartridges and three whose branches are confined to their own cartridges. Retinula axons terminate either in the lamina or the medulla neuropiles. There are three types of centrifugal neurons, two types of horizontal neuron, as well as glia and trachea in the lamina neuropile. The development of the lamina neuropile is described in terms of developing monopolar and centrifugal axons, growing retinula fibres, and composition of the developing optic cartridges.MSN was supported in part by a Fulbrights-Hays Scholarsship. We are grateful to the Science Research Council for its grant to PMJS.