Mitotic Index of Endosymbiotic Dinoflagellates in the Sea Anemone Stichodactyla haddoni under Harsh Environmental Conditions of the Persian Gulf and the Gulf of Oman

In the present study, the impact of physical and chemical factors in different seasons on the mitotic index (MI) and density of Symbiodinium was examined on a spatial basis for the sea anemone Stichodactyla haddoni. Adult S. haddoni were collected from three sites along the Persian Gulf (Qeshm Island (Dukuhak) and Hormuz Island) and the Gulf of Oman (Chabahar Bay) in the middle of the summer and in the winter from 2018 to 2019. Physical and chemical water quality parameters such as temperature, salinity, pH, and dissolved oxygen were measured at all study sites. The results showed that the density of Symbiodinium sp. depended on the season and temperature; the highest density of Symbiodinium sp. in S. haddoni was recorded for the winter specimen from Hormuz Island (31.70 × 106 cell/g at a temperature of 22°C) and the lowest density was recorded for the white specimen from Chabahar Bay (1.12 × 106 cells/g), when sea anemone bleaching was observed in the summer. The findings also showed that the highest and lowest MI values were recorded from the Chabahar Bay samples at 25.83 and 1.83%, respectively. A Pearson’s correlation heatmap illustrated the relationships between MI and physical and chemical factors. Oxygen percentage content, salinity, and wind speed were the main environmental factors influencing MI.