Abstract
Understanding the basis of the marine food web is essential in determining the uptake and possible control of the toxins that cause ciguatera fish poisoning (CFP), predominantly ciguatoxins. Ciguatoxins are produced by the marine, epiphytic dinoflagellate Gambierdiscus, and when transferred through the food web via herbivory, have serious environmental and health implications. Ciguatera outbreaks are common in coral reef environments where macroalgae are present. As ocean conditions change and more coral reef ecosystems shift to macroalgal domination, the risk of ciguatera outbreaks may increase. Since the first discovery of causal agents for CFP, the general consensus has been that the ciguatoxin pathway goes through herbivorous fish; however, some previous studies have suggested that herbivorous invertebrates may be another vector. Because hogfish have been found to be one of the high-risk fish species for CFP, and they are also known to consume invertebrates, more studies are necessary in order to accurately evaluate the invertebrate role as a vector. Therefore, the purpose of this study was to determine the grazing preferences of various herbivorous invertebrates on the common macroalgal hosts of Gambierdiscus, in order to examine the uptake of ciguatoxin into the food web. Four marine macroalgae were tested (Laurencia gemmifera, Halimeda incrassata, Dictyota menstrualis, and turf algae) against three different taxa ((Cerithium (Thericium) eburneum algicola (var.) (middle-spined cerith gastropods), Clibanarius tricolor (three-colored hermit crabs), and Lytechinus variegatus (variegated sea urchins)) of herbivorous invertebrates. Consumption rates were determined from changes in algal biomass. Direct G. silvae consumption rates were also determined for one species of invertebrate in a supplemental study. The experimental results indicated that there was a significant food preference for turf algae among all three species tested. There was also a significant food preference for Dictyota menstrualis for two of the species tested and Laurencia gemmifera for the other species tested (sea urchin). These results of this study have expanded our knowledge on herbivore feeding preferences and toxin uptake, which may lead to a better understanding of this crucial step in the introduction of ciguatoxin into the reef food web.
