Sensory mechanisms utilized by coral planulae to detect settlement cues

Meeting Abstract

5.3  Wednesday, Jan. 4  Sensory mechanisms utilized by coral planulae to detect settlement cues TRAN, C*; HADFIELD , MG; University of Hawaii at Manoa; University of Hawaii at Manoa

Coral planulae require environmental cues on substrata to settle and metamorphose into polyps. Sensory cells used to detect settlement cues are located in the apical region of many other marine invertebrate larvae. To determine what region of the body in coral larvae bears sensors for environmental cues, individual larvae were transversely sectioned into two separate oral and aboral fragments at various levels ¼, ½, and ¾ of the body length from the aboral pole. These separate ends heal and continue to swim until a suitable substratum, such as a marine biofilm, is introduced. A comparison was done with larvae of two coral species, Pocillopora damicornis and Montipora capitata. When provided with a settlement-inducing substratum, aboral ends of M. capitata settled while oral ends continued to swim as expected, given the aboral end is the point of attachment to the substratum. However, in larvae of P. damicornis, ¾ oral ends, i.e., lacking the aboral pole, were also able to settle. This is consistent with the results when larval sections were also provided with an artificial inducer, cesium chloride. These results suggest that the cells used to detect cues may not be limited to the aboral pole, but are instead distributed along the sides of the body as well in the aboral half. This is further supported by the observation of planulae rotating on their sides when exploring a biofilmed surface. The results of this study suggest that different coral species either utilize different sensory cells for chemoreception of settlement cues, or the cells are located on different regions of the larval body.

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