This work addresses an interesting, interdisciplinary problem of nature- "the mechanism by which animal senses the earth's magnetic field and navigate". Currently there are two existing theories trying to explain, "How the
animal senses the magnetic field of earth". One theory is based on the presence of biogenic magnetic materials in the body of the animals. Such magnetic materials which are present inside the body, orients itself according
to the earth's weak magnetic field and convey the information to the nervous system to develop the navigational map. The second theory is based on a light dependent photochemical reaction. A photochemical reaction leads to the generation of radical pairs, which helps in sensing the weak magnetic field of the earth. In this work, we are proposing a new model of magnetoreception. Unlike the existing radical pair system of magnetoreception, where a light-dependent reaction is essential to generate free radicals, here we show the presence of a large pool of stable carbon-centric free radicals in the nano-domains of the antennae and the wings of silk moth. This stable pool of carbon-centric free radicals is intrinsic in the nano-domains of these anatomical structures and responds to weak magnetic fields similar to that of Earth's (50 T) even in the absence of light. Hence we are proposing that nocturnal animals in their navigation could utilize such a light independent mechanism. We further observed the presence of ferromagnetic elements (Fe, Ni, Co, Mn) in these structures. In conclusion, we have discussed how carbon centric free radicals along with other ferromagnetic components present in the
antennae and the wings of the nocturnal silk moth, might help them to avoid the bats.
The work was supported by IITK start-up Grant (IITK/BSBE/20100206) of MD. MR is a senior research fellow of CSIR, India (Fellowship Number:09/092(0670)/2009-EMR-I). This work is part of MR's doctoral thesis and SKM's B.Tech. project. Authors are thankful to MMAE, chemistry, nano-science center (IITK) for VSM, ESR and SEM/EDX facilities respectively.