Micropuncture studies of formed-body secretion by the excretory organs of the crayfish, frog and stick insect.

In the course of investigations of the formation of urine by the antennal gland of the crayfish it was discovered that this process involved the secretion of formed bodies. The appearance and partial chemical analyses of the formed bodies of the crayfish are reported on elsewhere (Riegel, 1966). In the present report the lipid character of the walls of the formed bodies will be established, as will the fact that they contain digestive enzymes. Further, the results of similar studies on other excretory organs will be presented. A number of lines of evidence prompted the writer to suspect that formed bodies are to be found in two organs whose structure and function have been well studied. These are the vertebrate glomerular nephron and the insect Malpighian tubule. The proximal portions (coelomosac and labyrinth) of the antennal gland show striking histological similarities to the proximal portions (renal capsule and proximal tubule) of the vertebrate nephron. This is especially true when electron micrographs are compared (Anderson & Beams, 1956; Farquhar & Palade, i960; Kiimmel, 1964; Pease, 1955). Furthermore, both organs have much in common functionally. For example, the dyes Congo red and phenol red are accumulated by cells of the proximal portions of both, as is albumen. Further, the potassium concentration is elevated above blood levels (Oken & Solomon, i960; Riegel, 1965). Unpublished work indicates that bound potassium is associated with the formed bodies in the crayfish urine. This may be an explanation of the elevated potassium levels in the proximal portions of both types of excretory organ. Electron micrographs of the crayfish antennal gland and insect Malpighian tubule also show striking similarities (Beams, Tahmisian & Devine, 1955; Wigglesworth & Salpeter, 1962). Furthermore, as established by Ramsay (19556), the potassium concentration within the Malpighian tubule of Dixippus morosus is high compared with haemolymph levels.