The open oceans are harsh and hostile environments where insects might not be expected to thrive. In fact, only one insect group, ocean skaters, or water striders, has adapted to life on the open seas.
How these insects evolved to conquer the high seas, however, was not known.
Now, a study of the genetics of skaters provides a clue. The answer has to do with when major currents in the eastern Pacific Ocean came into existence with each species of skater evolving to match the unique conditions of those currents.
Scientists from the National University of Singapore (NUS) and Scripps Institution of Oceanography at UC San Diego examined the genetics of three ocean skater species collected with dip nets across the eastern Pacific between Hawaii and Peru. The results of the study revealed that the skaters became specialised on different current systems, as those currents changed into their modern configurations.
The findings could unravel the mystery of how each skater species came to occupy habitats vastly different from those of other insects, and also deepen our understanding of how climate change affects ocean-dwelling organisms.
“It is amazing how the ocean skater’s genetic history is closely tied to that of our oceans,” said study leader Dr Wendy Wang, an entomologist from the Lee Kong Chian Natural History Museum at NUS. “The open ocean is an extremely hostile environment, with direct sunlight throughout the daytime, strong winds and limited food. The abilities of their body covering or cuticle to protect their internal organs from heat and ultraviolet damage, and to survive violent storms and find food in this unique habitat where no other insect could demonstrate their unique ecological roles in the ocean. These characteristics make them fascinating subjects of study for materials science and extreme biological adaptations.”
The research team first reported their findings in the journal Marine Biology on 6 September 2021.
Linking genetic data with climatic changes
Ocean skaters live their entire lives perpetually running about on the surface film of the open seas, enduring lashing storms and feeding on tiny prey trapped on or just below the ocean surface. Currently, there are five known oceanic species of the genus Halobates. While information about where they can be found are well-established, little is known about their genetic variation, and how physical factors like ocean currents, temperature and winds affect their distribution.
The research team conducted a genetic study of three of those skater species collected from offshore Mexico to Peru, and as far out to sea as Hawaii. Most of the specimens were skimmed from the ocean surface with dip nets by Dr Lanna Cheng, a marine biologist at Scripps Oceanography, and study co-author. Dr Cheng is a world expert who has devoted her research to Halobates, and she has been studying the genus for almost five decades.
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