Locust Flight Notes

Central pattern generators and proprioceptive feedback - locust flight Locust good experimental animal as it is very robust - needs to be, as lives in dry challenging environments. Some migrate over long distances. Extremely good at manoeuvrable flight and reacting to environmental change. Locust has very good compound eyes and is very reliant on vision for controlling behaviour and deciding on direction of flight and finding food. Looking at behavioural analysis of flight behaviour Has two pairs of wings attached to 2nd and 3rd thoracic segments. You can study flight behaviour while animal stationary - stabilise body in wind tunnel and run wind over animal. Wind stimulus over head triggers the animal to flap its wings, so you can study reactions to wind velocity and direction etc. You can also place very fine wire electrodes in to record from different muscles at base of wing - record in terms of co-ordinated contractions of muscles during wing beat cycle. Wing beat normally around 20Hz (20bpm). Hindwings lead the cycle, are always slightly ahead of forewing by around 7ms. CPG circuit in to circuits must be co-ordinated to produce slight phase lag. Each wing has 10 muscles controlling wing beat - 4 depressor muscles and 6 elevator muscles per wing. Muscles can also control angle of wing to alter angle of attack so it gets lift as well as forward movement, resulting in very complex behaviour. Can steer as well. Steering requires adjusting the power put into wing beats on each side as well as angle. Must also be able to adjust height. Also need cycle-by-cycle adjustments because wind isn't always continuous and steady. Duration, phase of muscle contraction and also intensity of contraction must be adjustable on cycle-by-cycle and also over a longer term. On the vertical axis is degrees and 0 degrees is the wing down, 180 is wing up and red line shows hindwing and black shows forewing. Can see forewing lags slightly. One cycle is around 15/16ms. What the grey blocks show is a diagrammatical representation of electrical activity in certain muscles. Top are depressor, bottom are elevator. Forewing depressor muscles become active just before wing starts to come down and elevator active slightly before wing starts going up. For hindwing, depressor muscles slightly active before depressor muscles of forewing. Studying them easy as can be tethered and electroded. Neural circuitry of the locust Each one of these muscles must be innervated by one or more motorneurons and synapse with the muscles. Motor neurons must fire just before activity in muscle, all located in thoracic ganglia. Brain is the biggest ganglia in nervous system as it deals with sensory input coming into the head. Encounters change in environment first with its head. There is a suboesophageal ganglia and three thoracic ganglia, one in each segment of the thorax. The mesothoracic ganglion and the metathoracic ganglion are located in the 2nd and 3rd thoracic segments, where the wings are located. Meso controls forewing and meta 

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