PT  - JOURNAL ARTICLE
AU  - Murphy, David W.
AU  - Adhikari, Deepak
AU  - Webster, Donald R.
AU  - Yen, Jeannette
TI  - Underwater flight by the planktonic sea butterfly
AID  - 10.1242/jeb.129205
DP  - 2016 Feb 15
TA  - The Journal of Experimental Biology
PG  - 535--543
VI  - 219
IP  - 4
4099  - http://jeb.biologists.org/content/219/4/535.short
4100  - http://jeb.biologists.org/content/219/4/535.full
SO  - J. Exp. Biol.2016 Feb 15; 219
AB  - In a remarkable example of convergent evolution, we show that the zooplanktonic sea butterfly Limacina helicina ‘flies’ underwater in the same way that very small insects fly in the air. Both sea butterflies and flying insects stroke their wings in a characteristic figure-of-eight pattern to produce lift, and both generate extra lift by peeling their wings apart at the beginning of the power stroke (the well-known Weis-Fogh ‘clap-and-fling’ mechanism). It is highly surprising to find a zooplankter ‘mimicking’ insect flight as almost all zooplankton swim in this intermediate Reynolds number range (Re=10–100) by using their appendages as paddles rather than wings. The sea butterfly is also unique in that it accomplishes its insect-like figure-of-eight wing stroke by extreme rotation of its body (what we call ‘hyper-pitching’), a paradigm that has implications for micro aerial vehicle (MAV) design. No other animal, to our knowledge, pitches to this extent under normal locomotion.