Localized inhibition of cnidocyte firing by light in the sea anemone Anthopleura sola


Meeting Abstract

P1.76  Friday, Jan. 4  Localized inhibition of cnidocyte firing by light in the sea anemone Anthopleura sola BENDRICK-CHARTIER, E.M.*; LEUNG, N.Y.; OAKLEY, T.H.; Univ. of California, Santa Barbara; UCSB; UCSB ellabc@gmail.com

Firing of complex, engergetically expensive cnidocytes is influenced by chemosensory and photosensory cues in cnidarians, but the organismal function of the light behavior remains unknown. As previously shown in Hydra magnipapillata, we demonstrate that light environment affects cnidocyte firing behavior in the sea anemone Anthopleura sola. When mechanically stimulated, bright light inhibits firing compared to dim light. We illuminated half of each anemone with various LEDs (470, 510, 600, and 635 nm) and quantified the microbasic p-mastigophore (mpm) cnidocyte firing response in illuminated and shaded regions of the animal. We captured more mpm nematocysts from shaded regions of the animal than from illuminated regions. Therefore light inhibition of cnidocyte firing is a localized response that can differ among regions of the anemone. This photosensory response differs from chemosensory responses, which were shown previously in Haliplanella luciae to be integrated systemically. The absence of an integrated light response may inform the organismal function of the light behavior. First, a localized response would be unnecessary if light is being used as a diurnal signal to maximize firing during night time, when zooplankton prey are likely to be more abundant. Second, even though some genetic components of phototransduction and chemotransduction are shared in Cnidaria, the differing organismal responses suggest the genetic cascades are decoupled. Third, a localized light response is consistent with local shadows cast by prey increasing firing propensity. Fourth, a localized light response could mediate differential investment in “hunting” for regions of the animal in dim light that cannot make strong use of photosynthetic symbionts. Firmly establishing the organismal function of light-mediated cnidocyte firing will require further experimentation.

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