Body movements and their role as triggers of heartbeats in pupae of the Colorado potato beetle Leptinotarsa decemlineata

Rhythmic body movements and their role as triggers of intermittent heartbea ts were studied in pupae of Leprinotarsa decemlineata Say. Heartbeats and b ody movements were recorded simultaneously by means of an optical method (i nfra-red cardiography) combined with respirometry. IR-cardiography allows h eartbeats and body movements to be distinguished on the basis of their diff erent rates (40-80 min(-1) and 4-8 min(-1), respectively) and amplitude. In the mid-interecdysial period, abdominal movements in the pupae were alwa ys accompanied by heart activity beginning after the first 5-12 abdominal s trokes. Simultaneous periods of abdominal movements and heartbeats lasted 2 -5 min, while the intervening pause ranged from 40 to 72 min at 24 degreesC . Experiments of forced heart activity showed that a slight external tactile stimulus (prodding once with a single hair), applied prior to an expected h eartbeat bout, evoked abdominal movements followed soon afterwards by contr actions of the dorsal vessel. Repeated prodding with a hair evoked body rot ating movements (1-3 strokes) at any time with heartbeats starting at the f irst movement. We surmise that rhythmic body movements play an active role in the triggeri ng of heart activity in pupae according to the principle of cardiac reflex response. This is a possible mechanism for synchronizing periods of heart a ctivity with periods of rhythmic body movements. Haemolymph circulation in pupae is favoured when heartbeat bouts are accompanied by active body movem ents.