Mechanisms, ultrastructure and behavioral flashing in Ctenoides ales: “disco clams”

摘要

Dynamic visual displays throughout the animal kingdom are often bright and dramatic. They can be produced through a variety of photic processes including bioluminescence,the use of chromatophores, and structural coloration. Here we describe the mechanism underlying the striking display of the “disco" or “electric" clam， Ctenoides ales (Limidae),the only species of bivalve known to have a behaviorally mediated photic display and whose flashing is so vivid that it has been repeatedly confused for bioluminescence. The flashing display occurs on the mantle lip, where electron microscopy revealed two distinct tissue sides; one highly scattering side containing dense aggregations of spheres composed of silica, and one side containing a strongly absorbing pigment. High-speed video confirmed that the two sides of the mantle lip act in concert to create a vivid broadband reflectance that rapidly alternates with strong absorption in the blue region of the spectrum. Optical modeling suggests that the diameter of the spheres, but not their packing density, is nearly optimal for scattering visible light. This simple mechanism produces a remarkable optical effect that may function as a signal.