Meeting Abstract

22.2  Friday, Jan. 4  Mechanisms of egg defense in Megapodes: avoiding infection in a compost heap D’ALBA, L*; JONES, D; BADAWY, H; SHAWKEY, MD; University of Akron; Griffith University; University of Akron; University of Akron ldalba@wooster.edu

Interactions, over evolutionary time, between bacteria and vertebrate animals remain poorly understood. Infection is an important source of mortality for avian embryos but parental behaviors and eggs themselves can provide a network of antimicrobial defenses. Australian brush-turkeys (Alectura lathami) are unique among birds in that they produce heat for developing embryos not by sitting on eggs but by burying them in carefully tended mounds of soil and microbially decomposing vegetation. Despite the extremely high microbial abundance in these mounds, brush-turkey eggs are rarely infected, suggesting that they possess strong defensive mechanisms. To identify these mechanisms we first quantified antimicrobial albumen proteins and characterized eggshell structure, finding that albumen was not unusually antimicrobial, but that eggshells present a cuticle composed of nanometer-sized calcite spheres. Experimental tests revealed that these modified eggshells were significantly more hydrophobic and better at preventing penetration into the egg contents than control eggs. Our results show that the mutualistic cultivation of bacteria by megapodes has necessitated the evolution of novel defense mechanisms against parasitism.