Abstract

The dinoflagellate, Symbiodinium, forms symbiotic associations with a wide variety of marine invertebrates. In mollusks, Symbiodinium has been documented in bivalves and nudibranchs and recently has been identified in the gastropod Strombus gigas. Conch originating from Puerto Morelos, Cozumel, and Banco Chinchorro from the Mexican Caribbean were dissected, and dinoflagellates were found in the digestive gland, stomach, nephridium, gills, mantle, and foot, while no evidence of Symbiodinium was found in the gonad or muscle tissue. The number of dinoflagellates present in the conch reaches up to 5.22 x 108 Symbiodinium cells per organism in adults. The dinoflagellates show no signs of digestion or damage suggesting that they are not a dietary source for the conch. In addition, the ability of the dinoflagellates to do photochemistry implies that they are capable of providing the host with photosynthetically-derived carbon. Using histology, the distribution of Symbiodinium was determined to not be homogeneous in the different organs and tissues of the conch. The presence of the dinoflagellate in structures that are not directly related to the digestive system suggests that Symbiodinium plays an important role in the life cycle of the conch.

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