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Locust Phase Change
Locusts can change reversibly between two forms, or phases, that differ radically in appearance, physiology and behaviour. These transformations are driven entirely by population density and occur over timescales ranging from hours to generations. As such locusts are a powerful model with which to analyse mechanisms that underly phenotypic plasticity and its functional consequences as animals adapt to changing environmental conditions.
Locusts usually occur in a solitarious phase that actively avoids other locusts, are a drab green or brown camouflaged colour, and walk slowly and intermittently. By contrast the gregarious phase is attracted to other locusts and forms cohesive groups with them. They have bright warning colours as nymphs and walk rapidly and frequently. Whilst changes in morphology and physiology can take several generations to fully develop, behaviour is much more labile: A few hours of enforced crowding are sufficient to completely change a solitarious locust to gregarious behaviour. This is a vital pivot point in the process, once locusts behave gregariously, the resulting group cohesion drives the slower changes in physiology and morphology. We take an integrative approach that links changes in the sensory environment to changes in neuronal circuits, brain structure and behaviour. Accordingly we make use of a wide range of techniques including the quantitative analysis of behaviour, electrophysiology of identified neurones and circuits, laser confocal microscopy and image analysis, and biochemical and molecular analysis of neural signalling mechanisms. We are particularly interested in
- The molecular mechanisms that mediate changes in behaviour
- Where in the nervous system these changes occur
- How changes in neuronal function underlie the behavioural changes
- The time course of plasticity
- The sensory stimuli that mediate group attraction and repulsion
We have recently obtained strong evidence that serotonin plays a critical role in the initial stage of behavioural gregarisation.
- Rogers SM, Newland PL (2002) Gustatory processing in thoracic local circuits of locusts. J. Neuroscience 22, 8324-8333.
- Rogers SM, Newland, PL (2003) The neurobiology of taste in insects. Adv. Insect Physiol 31, 141-204
- Rogers SM , Matheson T, Despland E, Dodgson T, Burrows M, Simpson SJ(2003). Mechanosensory-induced behavioural gregarization in the desert locust Schistocerca gregaria. J. Exp. Biol.206, 3991-4002
- Opstad R, Rogers SM, Behmer ST , Simpson SJ (2004) Behavioural correlates of phenotypic plasticity in mouthpart chemoreceptor numbers in locusts. J. Insect Physiol. 50 , 725-736
- Rogers SM , Matheson T, Sasaki K, Kendrick K, Simpson SJ, Burrows M. (2004). Substantial changes in central nervous system neurotransmitters and neuromodulators accompany phase change in the locust. J. Exp. Biol.207, 3603-3617
- Matheson T, Rogers SM, Krapp HG (2004) Plasticity in the visual system is correlated with a change in lifestyle of solitarious and gregarious locusts. J. Neurophysiol. 91, 1-12.
- Rogers S M , Krapp HG, Burrows M, Matheson T. (2007) Compensatory plasticity at an identified synapse tunes a visuomotor pathway. J. Neurosci. 27 4621-4633.