Migration Literature Review

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Magnetic Navigation

Papers: Alerstam 2003, Boles & Lohmann 2003, Gould 2008, Johnsen & Lohmann 2005, Klimley et al. 2005, Lohmann et al. 2008, Meyer et al. 2005, Phillips et al. 2002, Wiltschko & Wiltschko 2005

Johnsen & Lohmann (2005) provide a good summary of magnetic field perception abilities in animals: there are 3 hypotheses for how magnetoreception works in animals, electromagnetic induction, magnetic field-dependent chemical reactions and biogenic magnetite, for none of which direct evidence exists. The earth's magnetic field can provide 2 types of information: compass information, which allows an animal to maintain a particular heading (i.e. head north) and geographical position, which allows an animal to navigate complex routes or find home and could be based on inclination angle or field intensity or the animal learning the 'magnetic map' (local anomalies) in their location. Electromagnetic induction is believed to be used by elasmobranch fish by means of detecting the Lorentz force of a charged particle moving though a magnetic field where the electric circuit is formed by the seawater as the conducting medium. The induction mechanism can detect polarity, but is probably not sensitive enough to be used as a magnetic map. The chemical magnetoreception mechanism relies on an electron transfer in a radical pair induced by light absorption. It is believed to be used by birds, newts, and flies, in which changes in magnetic orientation have been observed in response to specific in wavelengths of light. The chemical mechanism cannot detect polarity (merely the poleward direction rather than north or south) and cannot detect very small changes in field intensity necessary for a magnetic map. The biogenic magnetite mechanism comes in 2 types: single-domain magnetite, which are permanently magnetized crystals and will rotate into alignment with the earth's magnetic field, and superparamagnetic magnetite, which are smaller crystals and not permanently magnetized so they won't rotate, but the crystal's magnetic axis tracks the ambient field's axis. There is evidence of single-domain magnetite in fish noses, superparamagnetic magnetite in the upper beak of pigeons and other birds, and magnetite receptions in other animals such as turtles and mole rats. Single-domain magnetite mechanisms could detect polarity, though superparamagnetic magnetite mechanisms could not, though both could detect small changes in intensity to function as a magnetic map sense. Wiltschko & Wiltschko (2005) cover the 3 hypothesized magnetoreception mechanisms as well and also discuss field inclination and/or intensity being used as a 'signpost' in navigation with examples of birds and turtles. Gould (2008) turns to the evolution of magnetic sense stating with certain micro-aerobic bacteria containing chains of magnetite which serve to align them which the earth's magnetic field (and thus swim down away from the oxygen-laden surface). He considers the diversity of map and compass systems, and suggests that the chemical mechanism has evolved at least twice as a (partial) replacement for a magnetite mechanism based on the discovery of a vestigial fixed-direction compass in robins.

Additionally, several papers discuss evidence of magnetic navigational capabilities. Boles & Lohmann (2003) show that spiny lobsters (Panulirus argus) move in a homeward direction after being displaced, deprived of visual and magnetic cues during displacement, and having their eyes covered. When tested with magnetic fields replicating the locations ~400 km N and S of the testing site, the lobsters moved in the direction home would have been, had they been at these locations, showing a magnetic map sense. Alerstam (2003) places the work of Boles & Lohmann (2003) is a larger context with the history of considering animals using the earth's magnetic field for navigation on open future questions. Similarly, Phillips et al. (2002) showed evidence of a magnetic map sense in newts (Notophthalmus viridescens) sensitive to small differences in the magnetic field; displaced newts navigated towards home when subjected to a magnetic inclination simulating -0.5° from home, and did not display a significant directional orientation when the magnetic field simulated that of their home pond. Klimley et al. (2005) used telemetry to track bat rays (Myliobatis californica) to show the bat rays moved in a straight-line highly directional manner indicative of a compass or piloting sense. Meyer et al. (2005) showed sharks (Carcharhinus plumbeus and Sphyrna lewini) could detect an earth-strength magnetic field using conditioning for a food reward.

Further investigation:

  • Kalmijn, A. J. 1982 Electric and magnetic field detection in elasmobranch fishes. Science 218, 916–918.
  • Walker, M. M. et al. Structure and function of the vertebrate magnetic sense. Nature 390, 371–376 (1997).
  • Diebel, C. E. et al. Magnetite defines a vertebrate magnetoreceptor. Nature 406, 299–302 (2000).
  • Quinn, T. P. et al. Magnetic field detection in sockeye salmon. J. Exp. Zool. 217, 137–142 (1981).
  • Mann S, Sparks NHC, Walker MM, Kirschvink JL (1988) Ultra-structure, morphology and organization of biogenic magnetite from Sockeyes salmon, Oncorhynchus nerka: implications for magnetoreception. J Exp Biol 140:35–49
  • Quinn TP (1980) Evidence for celestial and magnetic compass orientation in lake migrating sockeye salmon fry. J Comp Physiol 137:243–248291:433–434
  • Quinn TP, Brannon EL (1982) The use of celestial and magnetic cues by orienting sockeye salmon smolts. J Comp Physiol 147:547–552
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