X-ray microanalysis of cockroach fat body in relation to ion and water regulation

X-Ray microanalysis of fat body from the cockroach (Periplaneta americana) showed that the crystals in the urate cells sequestered potassium and sodium during water deprivation. Postassium sequestration appeared to occur by the formation of additional crystals whereas sodium appeared to be taken up by pre-existing crystals of the “amorphous granule” type. Urate cells increased in cytoplasmic density i.e. mass per unit volume as a result of water deprivation and lost potassium from the cytoplasm but not from the nucleus. Trophocyte cells also showed an increase in density and a loss of potassium from the cytoplasm. The nucleus in trophocyte cells however, did not increase in density and showed an increase in chlorine concentration. A previously undescribed type of crystal in the trophocyte cell cytoplasm also increased markedly in chlorine concentration. The mycetocyte cells did not appear to increase in density but chlorine concentration was elevated in symbionts, cytoplasm and nucleus. An increase in density is considered to be a consequence of a reduction in volume due to water loss. It is confirmed that the fat body plays a major role in the maintenance of ion balance during water deprivation.