THE CORPUSCLES OF STANNIUS IN ARAWANA (OSTEOGLOSSUM-BICIRRHOSUM), AN ANCIENT TELEOST

The corpuscles of Stannius of arawana (Osteoglossum bicirrhosum), an a ncient teleost, were examined by routine light and electron microscopy and following their immunoreactivity to salmon and trout stanniocalci n antisera. Periodic acid-Schiff positive cells of the corpuscles of S tannius had a follicular arrangement and demonstrated a strong immunoh istochemical reaction with both stanniocalcin antisera. Fine structura l analysis of the paired, posteriorly located, and perirenal ovoid gla nds revealed two morphologically distinct cell types the basal laminae of which were ramified by nerve terminals. Immunecytochemistry demons trated that osmiophilic secretory granules in both cell types were imm unoreactive to the stanniocalcin antisera. When extracts of arawana co rpuscles of Stannius were subjected to sodium dodecyl sulphate electro phoresis and Western blot analysis a diffuse molecular weight band was evident (similar to 68 kDa) in the non-reduced condition. In all case s, immunoreactivity was abolished by preabsorption of the antisera wit h salmon stanniocalcin or with a crude extract of arawana corpuscles o f Stannius, The corpuscles of Stannius of arawana are similar to those in more recent teleosts with respect to cell structure and their anat omical distribution but their stanniocalcin is more similar in molecul ar weight to that present in at least one other non-teleost actinopter ygian (the gar) which has an ancient lineage.