Relationship between Cool Coma and Heat Coma Temperatures in the Oceanic Sea Skaters Halobates Collected near the Sumatra Island in the Indian Ocean

摘要

In the cruise, MR15-04 by R/V MIRAI, the samplings by the neuston net were performed in 23rd November to 14th December 2016 and three species of Halobates (H. germanus, H. micans, H. sp) were used for the temperature tolerance experiments after the collection. The neuston net was towed three times (3 × 15 min) on the starboard side of R/V MIRAI on the water surface with ship speed of 2 knot to water every 3 nights (19:00 - 20:00) at the fixed point in the south-western direction which was located at 50 km from the Sumatra island (4o03'S - 4o05'S, 101o53'E) in the Indonesia. Experiments on cool coma and heat coma were performed on the three species. Seconds for recovery from cool coma and heat coma were also examined on the Halobates in this study. Cool coma temperatures, gap temperature needed (temperature from the adapted temperature) for the cool coma and seconds for the recover from cool coma ranged 13.0oC to 25.0oC, 3.1oC to 16.1oC, 1 second to 4370 seconds, respectively. Heat coma temperature, gap temperature needed for the heat coma, seconds for the recover from heat coma ranged 29.4oC to 43.1oC, 1.9oC to 15.5oC, 2 seconds to 6420 seconds, respectively. The higher temperature of cool coma temperature during the last five days was shown when Madden-Julian Oscillation has passed over the ship, R/V MIRAI than the previous 10 days in the adults of H. germanus collected at the fixed place neat to Sumatra island (One way ANOVA: F-value = 2.314, df = 7, p = 0.028). Adults of un-described species, H. sp collected near to the Sumatra island, showed lower cool coma temperature [Mean ± SD: 15.51 ± 3.76 (9)] than those of H. germanus collected in the same place [16.96 ± 2.57 (191)]. This lower cool coma temperatures shown by this un-described species might be related to that this species should be a “shore” species inhabiting shore water in which many precipitation could cause the decreased surface temperature from 30oC - 31oC into about 25oC. Most of adults which suffered from the cool coma recovered within 20 seconds, whereas adults which suffered heat coma at 38oC and 39oC needed more than 200 seconds for the recovery and many of those which did it at more than 40oC needed more than 1000 second and some ones did not recover at all. All adults who suffered at more than 43oC did not recover at all. There were significant and negative correlation between cool and heat coma temperatures shown by the adults of H. germanus. This correlation might imply a common physiological mechanism for lower and higher temperature tolerances for this species.