Thermal tolerance of intertidal gastropods in the Western Arabian Gulf

Laboratory experiments were conducted to determine the thermal tolerance of the living shallow-water and intertidal gastropods from lagoons in Bahrain and Saudi Arabia, in the western Arabian Gulf. Our experimental trials, run in duplicate using a semi-controlled thermal incubator, quantify the thermal limits of two species of gastropods, the tropical periwinkle Planaxis sulcatus (Born, 1778) and the mud creeper Pirenella conica (Blainville, 1829), which are commonly found in the region. The two species display different thermal tolerances to heat exposure during this study. In the case of Planaxis sulcatus, we observe that half of the test specimens that are fully exposed to the air enter an inactive state or become comatose at about 39 °C, while half of specimens that are fully immersed in sea water become immobile around 42 °C. For Pirenella conica half of test specimens that are fully exposed enter become inactive at about 37.5 °C, while for specimens that are fully immersed in sea water this temperature is around 45 °C. At 60 °C total mortality is observed with no indication of recovery. These observations have implications for climate change predictions in the western Gulf region, as water temperatures in the lagoon already reach 42 °C in summer, while the substrate temperatures on mud flats exposed during low tide exceed the lethal limit of the gastropods during the summer months.