Abstract
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.
Highlights
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
H. germanus and H. micans were collected at only one station (St. 29 for H. germanus, St 32 for H. micans) of 13 stations in the Celebes Sea
The samplings of Halobates were performed as one set trial (15 min × 3 tows) per night and in total 9 nights in the tropical 2 stations in the eastern Indian Ocean showed that 12 - 330 individuals per the one-set trial of four species of Halobates germanus, H. micans, H. princeps and un-described and relatively large species, H. sp 2 (Table 1) [15]
Summary
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. Cross-Tolerance between Hardness to Lower and Higher Temperatures. There have been only a few reports on the cross tolerance between low and high temperature hardiness. One example of these reports is on a fruit fly, Drosophila melanogaster [8]. Harada et al [9] reported that a fresh water species of water strider, Aquarius paludum paludum, developed the cross tolerance as lower and higher lethal temperatures via the growth under a relatively low ambient temperature of 20 ̊C than a higher temperature of 25 ̊C, as a temperature acclimation affect. There have no studies on whether there is a cross tolerance between lower temperature and higher temperature in the sea skaters.
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