Fig. 1. Microscopic arrangement for the simultaneous measurement of haemoglobin (Hb) oxygen-saturation, heart rate, appendage beating rate and NADH fluorescence. The heart region of the animal was transilluminated with green light in the wavelength range 504–608 nm. Light that passed through this region was analysed spectrally to determine Hb oxygen-saturation. Using infrared transillumination at wavelengths above 780 nm, the periodic movements of the heart and the thoracic appendages were monitored by a light-sensitive CCD camera, and digital motion analysis was used to calculate heart and appendage beating rate. For alignment purposes, a longpass filter (LP 520) in front of the sensitive CCD camera attenuated, but did not completely block, the bright detection light beam used for Hb measurements. The central part of the animal was epi-illuminated with ultraviolet light at 365 nm to excite the pyridine nucleotides in the tissues, and the fluorescence image in the wavelength range 450–490 nm was collected by a light-sensitive SIT camera. The optical paths are visualized by different grey shadings. Dashed lines indicate light reaching the respective detector without having effects on the respective measurement. BP, bandpass filter; BS, beam splitter; DBS, dichroic beam splitter; f, focal length; Hal, halogen lamp; LG, light guide; LP, longpass filter; and ß, absorption bands of oxy-Hb.