The sea butterfly, a species of small predatory sea snail, may have a lot more things in common with flying insects than previously thought, a new study finds.
Limacina helicina, or sea butterfly, is a tiny swimming snail that lives in the northern Atlantic and Pacific Ocean. The snail uses translucent, wing-like appendages to navigate the cold waters. It has a shell that measures approximately one to four millimetres in diameter (0.04 to 0.16 inches); the colour of the sea butterfly’s soft parts is violet or dark purple.
In the study – published Wednesday (Feb. 17) in the Journal of Experimental Biology – the researchers found that the sea butterfly moved its appendages and swam is a completely different way than other zooplankton (tiny ocean animals) that also use paddles to propel themselves.
Dr. David Murphy, co-author of the study and a researcher from the Georgia Institute of Technology, said that he and his colleagues analysed the wing kinematics of the snail and found that it moved its wing-like appendages in a similar way that fruit flies beat their wings.
To capture the movements, the researchers used four high-speed cameras to record the sea butterflies as they swam in an aquarium. Dr. Murphy and fellow researchers also seeded the water with light-reflecting particles because they wanted to observe the movement of the water as the snails displaced it.
According to Dr. Murphy, the cameras helped them determine the 3D flow around the snail, and figure out the 3D position of each of the tiny, light-reflecting particles.
The results showed that the sea butterflies used a technique called ‘clap and fling’ to navigate around – which is a flying trick quite common in small insects. Murphy explained that the ‘clap and fling’ motion requires the animal to clap its wings and then fling them apart.
It took an entire day to setup, calibrate, and align the image-capture system, according to Murphy. Sea butterflies are also very fragile creatures, which is why it was also a challenge to keep them in good condition during their shipment from the West Coast. Fortunately, the tiny swimmers arrived safely and they were also very cooperative, the researchers noted.
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