A new ecotoxicity tolerance index of macrobenthos associated with Zoanthus sansibaricus in the littoral zone of Hormuz Island, Persian Gulf, Iran

Abstract

Palytoxin (PTX), one of the most potent marine natural products, which has been produced in zoanthids, also occurred in various other marine macrobenthos living in close association with zoanthid colonies, e.g. molluscs, accumulate high toxin concentrations in their organs, where PTX is stored in its active form. In littoral of Hormuz Island, among identified zoanthids, the highest number of toxic colonies per unit area is related to Zoanthus sansibaricus which can have a significant impact on assossiated macrobenthos with it. The purpose of this study was to collect more information on the toxicity of PTX in Z. sansibaricus and the consequences of exposure to PTX on associated macrobenthos with it using aqatic snails and the calculation of ecotoxicity tolerance index (ETI). Hence, zoanthid colonies were collected during reef walk at low tide in April 2016. Also, among assossiated gastropods, Planaxis sulcatus, were collected from the rock for experimental purpose as they are very abundant on and around Hormuz Island reef. In this model for each transect, 36 snails were divided into 4 set, each set had 3 replicates and working mucus solution, as PTX exist in the mucus of zoanthids, was injected in 2 different doses. Results showed that no snails were dead during the study period. However, calculation of Dara index (DI) was indicated that PTX accumulate in high toxin concentrations in snail's foot and thus snail can be introduced as an indicator of ecotoxicity conditions. Results of ETI, also were shown moderate poisoning in all transects. Hence, tolerance of marine animals to the toxin may enable it to enter food chains and to be followed by potential exposure for humans. However, due to lack of data on PTX of zoanthids research for the entire Persian Gulf, further investigation is needed to clearly ascertain this matter.