The attitudes of riparian communities to the presence of water hyacinth in the Wouri River Basin,Douala, Cameroon

Since publication of the first record of Eichhornia crassipes in Cameroon in 1997, the weed has become highly invasive in the Wouri River Basin. Between June and September 2014, a socio-economic survey using participatory and qualitative methods was undertaken in the riparian villages of the Wouri River Basin to assess the perception of respondents to the presence of water hyacinth. The survey revealed that water hyacinth was a significant threat to activities along the river, which included fishing, sand extraction and river transportation. The presence of water hyacinth mats reduced catch rates of several common fish species, river transportation by 75%, and significantly reduced the income for sand extraction. Cameroon employs manual clearing of water hyacinth; however, respondents indicated they would consider other control methods, provided they do not have any negative impacts.     

Behavioural evidence for polarization vision in crickets

ABSTRACT. Tethered field crickets, Gryllus campestris L., walking on an air-suspended bail exhibit a spontaneous response to the e-vector of polarized light presented from above: E-vector orientation controls strength and direction of turning tendency. Experiments in which different eye regions are covered with paint suggest that this response is mediated by the anatomically and physiologically specialized dorsal rim area of the compound eye. We conclude that crickets have polarization vision and that the dorsal rim area of the eye plays a key role in this sensory capacity.     

Membrane Impression and Gene Expression

The central question in the molecular biology of differentiation is: why are new parts of the genome transcribed? Different hypotheses have been suggested for the control of the cytodifferentiation process. Many of these postulate a "time programme"; others postulate a "programme of events", leading to the conversion of cells to new phenotypes. In the model discussed here the fatter postulate is favoured, suggesting that the differentiation process is guided by the continuous and sequential changes of the microenvironment of the cell. The knowledge of the regularity of these changes is integrated as "evolutive experience", as a more or less fixed programme into the genome. Specific structures in the cell membrane (receptors, receptor areas) are able to perceive and transduce the signal of the environment. The signal can be transformed and regulated in the cell on different levels. For this process—the information flux from the cell membrane to the genome—the term " membrane impression " is proposed in contrast to the information flux from the genome to the cell membrane " gene expression ". It is mentioned that the differentiation process corresponds to the alternative interaction between the cell membrane and the genome. This typical Ping Pong interaction results in cell lineage. It is postulated that membrane receptors for the next anticipated signals are coexpressed with a specific phenotype of the cell. The possibility of the existence of different receptors is discussed.