The origin and nature of the brown substance in the gut caeca of the polychaetes Aphrodite aculeata and Gattyana cirrosa



The brown fluid in the gut caeca of Aphrodite aculeata L. and Gattyana cirrosa (Pallas) contains haem, a non-haem brown pigment of unknown nature, but probably lipofuscin, and non-haem iron compounds. Evidence is presented to support the hypothesis that the haem in the fluid is derived from the food in the gut and is not endogenous, whilst the non-haem brown pigment is excreted into the lumen. Other substances are also secreted by the caecal epithelium.