Photochemical & Photobiological Sciences Dynamic Article Links Cite this: Photochem. Photobiol. Sci., 2012, 11, 345 www.rsc.org/pps PAPER Fireﬂy ﬂashing under strong static magnetic ﬁeld Anurup Gohain Barua,* a Masakazu Iwasaka, b,c Yuito Miyashita, b Satoru Kurita d and Norio Owada d Received 11th July 2011, Accepted 20th October 2011 DOI: 10.1039/c1pp05220a Fireﬂy ﬂashing has been the subject of numerous scientiﬁc investigations. Here we present in vivo ﬂashes from male specimens of three species of ﬁreﬂies—two Japanese species Luciola cruciata, Luciola lateralis and one Indian species Luciola praeusta—positioned under a superconducting magnet. When the OFF state of the ﬁreﬂy becomes long after ﬂashing in an immobile state under the strong static magnetic ﬁeld of strength 10 Tesla for a long time, which varies widely from species to species as well as from specimen to specimen, the effect of the ﬁeld becomes noticeable. The ﬂashes in general are more rapid, and occasionally overlap to produce broad compound ﬂashes. We present the broadest ﬂashes recorded to date, and propose that the strong static magnetic ﬁeld affects the neural activities of ﬁreﬂies, especially those in the spent up or ‘exhausted’ condition. 1 Introduction Bioluminescence is the production and emission of light by a living organism. The ﬁreﬂy, a common organism, produces its light in a multi-step process that could be outlined as follows. First, the enzyme luciferase converts ﬁreﬂy D-luciferin into the corresponding enzyme-bound luciferyl adenylate. Next, luciferase amino acid residues are recruited to promote the addition of molecular oxygen to luciferin, which is then transferred to an electronic excited-state oxyluciferin molecule and carbon dioxide. Finally, visible light is emitted as the oxyluciferin decays to the ground state via a ﬂuorescence pathway. Bioluminescence is used in the courtship signals of adult ﬁreﬂies and larval warning signals directed toward potential predators. In the past decade, new evidence that females choose their mates on the basis of male ﬂash behavior has been put forward. 1–3 Other new contributions include better understanding of the biochemical mechanisms behind ﬁreﬂy bioluminescence and ﬂash control, 4–7 the relationship between ﬁreﬂy chemical defenses and predation, 8–10 and the biodiversity and signaling behaviour of lampyrids in Japan, China, Europe and Brazil. 11–18 Recently, it has been shown that a typical collective rhythm occurring only among the males arises and it is followed by a response from the females. 19 One function of ﬂash synchrony is to facilitate a female’s ability to recognize her conspeciﬁc male’s ﬂashing by eliminating potential visual clutter from other ﬂashing males. 20 Very recently, it has been reported that the ﬁreﬂy’s emission intensity decreases transiently a Department of Physics, Gauhati University, Guwahati, 781014, India. E-mail: agohainbarua@yahoo.com b Graduate School of Engineering, Chiba University, 1-33 Yayoicho, Inage- ku, 263-8522, Chiba, Japan c Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi, 270-0133, Saitama, Japan d Research Centre, ABI Co. Ltd, 238-1, Judayu, Nagareyama, 270-1133, Chiba, Japan in static magnetic ﬁelds up to 10 Tesla, whereas both pulse density and frequency increase in a pulsed train magnetic ﬁeld. 21 It is believed that the ﬁreﬂy ﬂashes are shaped by neural impulses generated in the brain that eventually impinge on the lantern tissue. It is assumed to be possible to shape any kind of ﬂash by simply adjusting the frequency and duration of the stimulus activating the lantern nerves. 22 Octopamine is widely believed to be the neurotransmitter responsible for the induction of luminescence in the ﬁreﬂy lantern. It is detected in adult lanterns, 23,24 and in larval lanterns, lantern ganglia and photomotor neuron somata. 25 Behavioural experiments have demonstrated a ‘magnetic sense’ among diverse animals, birds being the best studied group by far. It is known that the magnetic vector of the earth’s magnetic ﬁeld provides a compass for the animals. 26,27 Magnetic intensity has been discussed as a component of the navigational ‘map’ of pigeons since the late nineteenth century. The avian magnetic compass is an inclination compass based on the inclination of the ﬁeld lines rather than polarity. 26 It has been shown that oscillating magnetic ﬁelds disrupt the magnetic orientation behaviour of migratory birds, suggesting a magnetic compass based on a radical pair mechanism. 28 It is indicated that birds use a radical pair with special properties, which is optimally designed as a receptor in a biological compass. 29 Domestic cattle across the globe, and grazing and resting red and roe deer have been observed to align their body axis in roughly a north–south direction, with magnetic alignment being the most parsimonius explanation. 30 We still do not have a complete understanding of the physiological and neurobiological processes associated with magnetoreception. The three most prominent hypotheses, based on fundamentally different principles, for the primary process underlying the magnetic compass involve (1) induction, which is restricted to marine animals as it requires sea water as a surrounding medium with high conductivity, (2) magnetite, a permanent magnetic material, and (3) a magnetically sensitive chemical reaction, known as the ‘radical pair’ model. This journal is © The Royal Society of Chemistry and Owner Societies 2012 Photochem. Photobiol. Sci., 2012, 11, 345–350 | 345