Heat coma as an indicator of resistance to environmental stress and its relationship to ocean dynamics in the sea skaters,Halobates (Heteroptera: Gerridae)

Abstract The tolerance to temperature increase was tested for Halobates individuals collected during two cruises in the western tropical Pacific Ocean (MR‐06‐05‐Leg 3, December 21, 2006–January 12, 2007, 0°N‐8°N; KH‐06‐02‐Leg 5, August 18–31, 2006, 12°N–17°N). High temperature coma experiments were conducted on adults and 5th instar larvae. On average, H. sericeus (distributed in the wide latitude zone of 5°N–40°N), H. germanus (distributed in the moderate latitude zone of 0°N–35°N) and H. micans (distributed mainly in the lower latitudes around the equator) were on average paralyzed at 35.6°C (SD: 0.89), 32.9°C (SD: 2.17) and 31.6°C (SD: 2.60), respectively (P= 0.035). According to the current dynamics during the cruise, the colony of H. sericeus at one station (5°N 137°E) may have been transferred from the northern area of 14°N by three currents (North Equatorial Current, Mindanao Current and North Equatorial Counter Current) to the area of 5°N 138°E. Extremely high heat resistance was shown by the adults of H. germanus in the sea area around the equator. Dynamic current and air movements in this area around the equator, that is a “warm seawater pool”, could be hypothesized to be related to the high resistance to heat shown in this study.