(full paper is archived in the Miller Library)
Title: Biochemical control of iridescence in the iridophores of Loligo Opalescens
Student Author(s): Adler, Michael J.
Faculty Advisor(s): Thompson, Stuart
Location: Final Papers Biology 175H
Date: June 1987
Keywords: biology of cephalopods
Abstract: Cholinergic receptors controlling iridescence in the iridophores of Loligo opalescens were found to be muscarinic. Selective agonists and antagonists were applied, and responsiveness was measured by a change in iridescence. Carbamylcholine and acetyl-beta-methyl-choline (AMBC) are group A muscarinic agonists that elicited positive response. Effective group B agonists included carbamyl-beta-methyl-choline (CMBC) and oxotremorine. Atropine, scopolamine, and pirenzipine are muscarinic antagonists that effectively hindered iridescence, while tubcurarine, a nicotinic antagonist, did not block iridescence. Agonist groupings are based on their abillity to turn over phoshatidylinositol (Phl). THe results of these agonists/antagonists combined with the effect of Li+ and subsequent addition of myo-inositol, show that Phl turnover may be involved. Li+ selectively inhibits a step in the Phl pathway. Li+ was found to decrease iridescence and addition of myo-inositol seemed to cause its reappearance. Ca++ seems to be involved, since addition of an agonist in zero Ca++ sea water did not result in iridescence. Addition of forskolin and caffeine resulted in a decrease in iridescence, inplying that high cAMP levels inhibit the response. From this data four receptor models were constructed.