Dr. Urzua-Osorio, Angel

Alexandrium catenella, one of the most common harmful microalgae observed in southern Chile, produces paralytic shellfish toxins, which can affect many organisms throughout the trophic chain. This research evaluated how paralytic shellfish toxins affected the principal bioenergetic constituents and fatty acids composition of the carnivorous snail Chorus giganteus. Snails were separated into a “toxic” group that was fed the toxic clam Mulinia edulis (which was previously fed A. catenella), and a “non-toxic” group, fed non-toxic clams. Both groups were kept under these conditions for 63 days. Our results indicated no difference in the ingestion rate of toxic versus non-toxic snails; however, a higher protein level was identified in toxic snails. The total lipid content proved to be no different in toxic versus non-toxic snails; although, an effect of the toxic diet on the fatty acid profile of C. giganteus was observed. High levels of essential polyunsaturated fatty acids, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in toxic snails, were identified. Our results suggest that exposure to paralytic shellfish toxins, through diet, may cause changes in the biochemical composition of C. giganteus, which may have a subsequent impact on its energetic physiology.

The producer of paralytic shellfish toxin (PST), Alexandrium catenella, is one of the main generators of HABs in the coasts of Chile. Its presence produces ecological and economic damage, directly affecting filter feeding organisms, and indirectly to other organism through the trophic chain. The objective of this research was to identify the effect of a toxic diet on the energetic and reproductive parameters of the carnivorous snail Chorus giganteus. Two groups of snails were used, one fed with toxic prey (bivalves fed with A. catenella), and the other fed with non-toxic prey. Both treatments were maintained under these conditions for 63 days, then, elemental composition (C, N) and energy content were estimated, and fecundity parameters were analyzed. The results indicate that snails fed with toxic prey had a lower percentage of C and C/N ratio. The energy content was significantly lower in intoxicated snails. Regarding fecundity parameters, a higher number of egg-masses were produced by toxic snails, however, only 62% of these showed embryonic development, with 57% hatching success. A negative relationship was identified between the mean PST concentration, quantified in snails, and the number of egg-masses produced per aquarium. In the aquarium where the snails had highest average PST concentration (1200 ± 820 μg STX.2HCL eq. Kg− 1) there was no oviposition, while egg-masses were only produced by snails in aquaria where the average concentration did not exceed 360 ± 160 μg STX.2HCL eq. Kg− 1. It is likely that, with low levels of accumulated PST, C. giganteus activates its oviposition process as a response to toxin-induced stress, generating a higher energy expenditure supported by a redirection of its reserves. However, when the intoxication presents higher levels, the reproductive process could be inhibited, similar to what has been identified in other molluscs.