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.

The First Finding of Six Instars of Larvae in Heteroptera and the Negative Correlation between Precipitation and Number of Individuals Collected in Sea Skaters of Halobates (Heteroptera: Gerridae)

“…The difference in the species component of oceanic sea skaters due to the latitude and distance from the islands may be related to cannibalism by a bigger species ( H. micans ) of a smaller one ( H. sericeus ) (Harada, unpublished), tolerance to variation in surface temperature [1,14,15] ( H. sericeus inhabiting a wider range of latitudes and with harder tolerance to temperature change) and salinity [16] ( H. germanus with a harder tolerance to lower salinity because of selection by heavy rain fall from inhabiting the area near the shore).…”

“…The cruise of MR06-04 by the R/V MIRAI was performed in the western tropical Pacific Ocean. More than 3000 eggs that had been laid on a piece of styrene foam were collected by an ORI (Ocean Research Institute of the University of Tokyo produced) net during this cruise [14]. These eggs were incubated and most 0th instar larvae hatched from the eggs [18].…”

Lowered Salinity Tolerance in Sea SkatersHalobates micans,Halobates sericeus, andHalobatessp. (Heteroptera: Gerridae)

“…Three of the above species, Halobates sericeus, H. micans, and H. germanus inhabit tropical and temperate areas of the PaciÞc Ocean in the northern hemisphere, including the Kuroshio Current and the East China Sea (Andersen and Polhemus 1976, Cheng 1985, Harada 2005. H. sericeus, H. micans, and H. germanus are reported from latitudes of 5Њ N-40Њ N, 0Њ N-35Њ N, and 0Њ N-37Њ N, respectively, in the PaciÞc Ocean (Miyamoto and Senta 1960, Andersen and Polhemus 1976, Ikawa et al 2002, Harada 2005, Harada et al 2011.…”

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

“…On the temperature tolerance of oceanic sea skaters, several studies have been done from multiple which has wide latitude distribution of 35˚S to 40˚N showed higher resistances to both higher lower and higher temperatures than the other two species of H. micans and H. germaus which had only narrow distribution mainly from 15˚S to 15˚S, because H. sericeus has suffered higher temperature fluctuations due to seasons in higher latitude places [1]. In H. sericeus, populations which have higher influence from the Kuroshio current showed higher resistance to lower temperature than other population which has little influence from current [5].…”

“…Studies on temperature tolerance have been done about heat tolerance [1][2][3][4] and those on cool tolerance are very limited to studies by Furuki et al [5], and Umamoto et al [6] in sea skaters. There have been no studies which examined both heat and cool tolerances on the same population and at the same time in insects.…”