AsianScientist (July 21, 2017) – The ribbon halfbeak (Euleptorhamphus viridis) may not have tail wings like other true flying fish, but it can nonetheless fly over the ocean surface by twisting its body by 90 degrees. These findings have been presented at the Society for Experimental Biology Annual Main Meeting.
“Other flying fish, including the Japanese flying fish, have large pectoral fins that act as wings during flight and large pelvic fins that are used as horizontal tail wings, like those on airplanes,” said Dr. Yoshinobu Inada from Tokai University, Japan. “However, the ribbon halfbeak lacks these large pelvic tail wings.”
“Amazingly, they solve this problem by rotating their rear body by 90 degrees and use their wide dorsal and anal fins as a horizontal tail wing.”
By 3D printing a physical model based closely on real ribbon halfbeaks and analyzing its flight performance with different tail wing positions in a wind tunnel, the researchers also learnt that ribbon halfbeaks need to lift their rear body above the main pectoral wings to reduce the effect of downwash on the tail wings. This improves the lift and flight performance of the fish.
“Other related fish species are also able to jump and fly over the sea surface, but only halfbeak twist their bodies for flight. This is a really unique behavior,” said Inada.
Mr. Junji Yonezawa, a study collaborator at the Tokyo Metropolitan Islands Area Research and Development Center of Agriculture, Forestry and Fisheries, believes that this interesting behavior may be the result of different evolutionary selective pressures to those faced by other flying fish, leading to unique adaptations.
“It has the largest number of vertebrae among Japanese halfbeaks, which means that it is able to twist the rear half of its body by a whole quarter-turn,” said Yonezawa.
This study sheds light on the poorly understood flying behavior of ribbon halfbeaks and could also provide useful information for the optimal design of tandem wing airplanes.
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Source: Society for Experimental Biology; Photo: Yoshinobu Inada.
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