Genbank accession #: AJ237597

Plant Molecular Biology -     

Changes in Fluid Intake suggesting Depressed Appetites in Rats with Central Catecholaminergic Lesions

THE catecholaminergic neurones of the mammalian brain are generally believed to be important in the control of voluntary behaviour and affect. The evidence for this comes from work with pharmacological agents which enhance or block the post-synaptic effects of noradrenergic or dopaminergic neurones^1–3. This has led to speculations implicating central catecholaminergic dysfunction in affective disorders such as depression^1,4,5 and in other disorders such as Parkinson's disease⁶ and schizophrenia^7,8. But research on the behavioural effects in animals of pharmacological interference with the normal functions of central catecholamines has been hindered by the fact that the sudden withdrawal of either noradrenaline or dopamine leads to behavioural sedation and inactivity^9–14, which precludes any fine analysis of behavioural deficits.     

Aggregative oviposition of a phytophagous beetle overcomes egg‐crushing plant defences

1. Gregarious behaviours in phytophagous insects are common, but their adaptive value is rarely well understood. In the present study, we document a novel case of cooperative behaviour, the aggregative oviposition of a leaf beetle, Pyrrhalta viburni Paykull, and the realised fitness benefit of overcoming a plant defensive response (wound tissue production). 2. In laboratory choice‐tests, females exhibited aggregative oviposition, characterised by (i) a preference for twigs already infested by conspecifics, and (ii) positioning of new egg masses adjacent to existing ones. Field observations supported laboratory results, showing that P. viburni egg masses are most commonly found aggregated in large clusters. 3. In a field experiment using three host plants (Viburnum dentatum L., Viburnum opulus L. and Viburnum×bodnantense Aberc. ex Stearn), mean egg survivorship and twig mortality increased, while twig wound response decreased, with an increasing level of infestation. Egg survivorship was consistently higher on twigs that died than on twigs that remained alive. 4. Overall, these results suggest that, by aggregating their egg masses, P. viburni females overwhelm the twig wound response, often killing the twig in the process. Aggregative oviposition and low defences of V. dentatum to P. viburni could have facilitated the establishment and spread of this beetle in its introduced range (northeastern North America), in areas where V. dentatum is abundant.     

Retention of cryptic genes in microbial populations

Cryptic genes are silenced genes that can still be reactivated by mutation. Since they can make no positive contribution to the fitness of their carriers, it is not clear why many cryptic genes in microbial populations have not degenerated into useless DNA sequences. Hall et al. (1983) have suggested that cryptic genes have persisted because of occasional strong environmental selection for reactivated genes. The present mathematical study supports their suggestion. It shows that a cryptic gene can be retained without having any selective advantage over a useless DNA sequence, if selection for the reactivated gene occasionally occurs for a substantially long time.