Adaptation of a quantitative programme for the X-ray analysis of solubilized tissue as microdroplets in the transmission electron microscope: application to the moult cycle of the shrimp Crangon crangon (L).

A quantitative programme for X-ray microanalysis is used in a non-standard manner on solubilized tissue which has been spiked with cobalt and sprayed as microdroplets on electron microscope grids. During the procedure the count time and the concentration of cobalt is related to the peak integral and, from the relative efficiencies, the concentrations of other elements are computed from the peak integrals. Absorption is taken into account but the X-ray background is not used to estimate the total mass and the beam current is not measured. The method is applied to the hepatopancreas and blood from individual shrimps, Crangon crangon, to give the concentrations of sodium, magnesium, silicon, phosphorus, sulphur, potassium and calcium at different stages of the moult cycle. In the hepatopancreas the absolute and relative quantities of phosphorus, sulphur and other elements change in phase with the moult cycle. This situation must be linked with fluctuations in levels of metabolic activity and may affect the metal-binding capacity of the tissue which is known to fluctuate. The hepatopancreas accumulates lipid and phosphorus during the intermoult period, but the level of phospholipid phosphorus remains as a constant proportion of the tissue wet weight. The gland does not store calcium for hardening the new exoskeleton after ecdysis. Magnesium is a more important and variable component and could be linked with metabolic activity. The blood composition remains more stable. However, sulphur concentration is high and variable and this may, to some extent, reflect changes in the concentration of taurine. The concentration of copper increases towards the end of the moult cycle and decreases during moulting; opposite changes occur in the hepatopancreas.