Meeting Abstract

78.6  Sunday, Jan. 6  Are the explosively launched spores of ascomycete fungi perfect projectiles, and is co-ordinated ejection used to achieve better-than-perfect range? ROPER, M.*; BRENNER, M.P.; PRINGLE, A.; Harvard University; Harvard University; Harvard University mroper@deas.harvard.edu

Minimization of drag appears to have left an imprint upon the evolution of bauplans of an enormous variety of species, both sessile and motile; from fast swimming pelagic fish to Mayfly nymphs that cleave to rocks in rapidly flowing streams. In spite of the apparent evidence of drag minimization of diverse body parts, the strength of the underlying selective forces, both historical and current, cannot be easily measured -- we do not know how sub-optimal an organism can afford to be in regard of drag before suffering loss of fitness. We determine the stiffness of the drag minimization constraint for the explosively launched spores of ascomycete fungi, showing that most singly ejected spores have shapes that match perfect projectiles: bodies of prescribed volume that are shaped to minimize the drag encountered in flight. Fungi deploy other mechanisms, beyond spore shape, in order to increase the distance traveled by their spores: a perfect projectile may yet find its range limited when launched into the adverse air flow that typically surrounds a fruiting body. Many species of cup fungi have evolved mechanisms for discharging large numbers of spores at once. We show how multi-sporic discharge may allow relaminarization of the turbulent flow of air over the fruiting body, ensuring that each ejected spore encounters a favorable wind. We probe the natural history of how these fungi acquired the ability to manipulate their fluid environment.