19.5 Sunday, Jan. 4 11:15 Flashing in Ctenoides ales "disco" clams: behavioral function and visual cues DOUGHERTY, L.F.*; NIEBERGALL, A.K.; CALDWELL, R.L.; University of California, Berkeley; University of California, Berkeley; University of California, Berkeley firstname.lastname@example.org
The “disco” clam Ctenoides ales has a vivid flashing display that results from a dense collection of silica nanospheres on one side of the mantle tissue which causes broadband reflectance. This tissue alternates rapidly with the opposite absorbent side. The fitness value of the flashing display remains unknown, as well as the visual ability to distinguish the display in conspecifics. Three hypotheses were tested; that the display acts in phototaxic prey luring, aposematic signaling, and/or conspecific recruitment. Effects of ecological variations in light intensity on flash rate were tested, and the visual capabilities of C. ales were assessed through transmission electron microscopy and opsin expression analysis. Prey luring and aposematism were tested by presenting clams with stimuli of food or predators, and analyzing flash rate 5s before and after the stimulus. Results showed a significant increase in flash rate to both. Conspecific recruitment was tested by dividing nine tanks in half using barriers and giving C. ales various stimuli to test settlement, orientation and proximity. Visual and chemosensory cues were controlled by inhibiting water flow, using opaque barriers, and implementing varying stimuli including other C. ales, video of C. ales, the non-flashing congener C. scaber, a rock or an empty control. Preliminary results indicate that both chemosensory and visual cues of C. ales caused the experimental C. ales to move closer than in the control tank. Varying intensities of blue light to mimic increasing depth showed no significant difference in flash rate. Preliminary analysis of visual capabilities suggests the pallial eyes of C. ales have light-detecting capabilities and may possess reflective pigments. Behavioral and optical analyses are ongoing.