Abstract
A series of studies were conducted during two cruises between Tokyo and Honolulu in September 2010 and from February to March 2012. The aims of the studies were to (1) compare the distribution of three species of Halobates oceanic skaters, H. germanus, H. micans, and H. sericeus, with respect to their temperature limits; (2) identify the lower temperature limit of H. sericeus, the species that displays the widest distribution range (40°N–35°S) latitude; and (3) test the hypothesis that H. sericeus can change their temperature tolerance to adapt to seasonal changes in sea surface temperatures. The heat coma temperature (HCT) was measured during the two cruises and the values were compared between the two populations of H. sericeus. The species collected in September 2010 were H. germanus, H. micans, and H. sericeus. H. sericeus was dominant, occupying more than 90% of the collecting sites. H. germanus and H. micans were collected in the northern and western part of the cruise track (29–34°N, 141–151°E), and not in the southern and eastern part. The population density of these two species was 9000–150,000/km2 in the first cruise, which took place in summer. On the other hand, H. sericeus was collected throughout the cruise track during that cruise. The population density of H. sericeus was relatively high, at 4000–310,000/km2, in the southern and eastern part of the cruise track (19–29°N, 152°E–165°W). In February and March 2012, only H. sericeus was collected at a density of 17,000–80,000/km2 and only in the eastern and southern part, at 25°–28°N, 169°E–178°W. No Halobates oceanic skaters were found in the western or northern part (30°N and further north, 159°E and further west) during that cruise. The lower limit for the inhabitation of sea surface temperatures appeared to be 27.8 °C or slightly lower for H. germanus and H. micans, but was 22.1 °C or slightly lower for H. sericeus. H. sericeus specimens, mostly adults, that had been collected during the two cruises were used in heat coma experiments. Summer specimens showed significantly higher heat coma temperatures (HCTs) than the winter specimens. This difference in HCTs may be the result of relatively long term temperature acclimation in the summer or winter for the adults that inhabit the temperate and subtropical areas along the cruise tracks between Tokyo and Honolulu in the Pacific Ocean. This temperature plasticity of H. sericeus may be related to the wider latitude area inhabited by this species (main range: 40°N–25°S).
Highlights
Insects are found everywhere from the Antarctic to the tropical terrestrial zone
These samplings indicated that four species, H. germanus, H. micans, H. sericeus, and H. sp. inhabited the region during the summer (H. sp.: possibly a new species inhabiting the open ocean; body length: 3.5–4.6 mm, longer thorax relative to body width; a formal description is in preparation)
The only location where all four species were collected was at 30◦ –34◦ N and 140◦ –144◦ E along the western part of the cruise track during the summer cruise, where H. sericeus was dominant
Summary
Insects are found everywhere from the Antarctic to the tropical terrestrial zone This wide distribution means that they are highly adapted to a wide ambient temperature range [1]. The lower ambient (water surface) temperature limit of oceanic skaters is said to be around 25 ◦ C for their distribution [3,4,5]. H. sericeus may be able to inhabit the subtropical oceanic area (around 25◦ N) even in winter, with surface sea temperatures of around 20 ◦ C–25 ◦ C, which may be the critical range for the distribution of this species. No data have been found on the critical inhabiting area showing the lower limit temperature of the oceanic skaters in the winter season.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.