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Biol Bull 127: 206-220. (October 1964)
© 1964 Marine Biological Laboratory
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A COMPASS DIRECTIONAL PHENOMENON IN MUD-SNAILS AND ITS RELATION TO MAGNETISM

FRANK A. BROWN JR. 1, H. MARGUERITE WEBB 1, and FRANKLIN H. BARNWELL 1

1 Marine Biological Laboratory, Woods Hole, Mass., and the Departments of Biology, Northwestern University, Evanston, Ill., and Goucher College, Towson 4, Md.

1. Mud-snails in a uniform field of all ordinarily controlled directional factors distinguish among geographic directions.

2. Geomagnetism is involved in this directional sense. This was shown by rotation of a 5-gauss horizontal magnetic field which produced an orientational behavior correlated with that observed when the snails were rotated in the opposite direction in the earth's field.

3. The response pattern to compass directions of the 5-gauss horizontal field was essentially the mirror-image of that observed for the earth's 0.17-gauss field.

4. The directional response of the snails in the geographic field, and the concurrent correlated response to a rotating experimental magnetic field, vary parallelly with time and with influence of other, still undefined factors.

5. Rotation of a 5-gauss horizontal magnetic field through the series of four compass directions, differing by 45° from the four cardinal directions, may produce a pattern of compass-directional behavior either paralleling or mirror-imaging that observed concurrently for the four cardinal directions.

6. The compass-directional pattern of response of the snails shows a monthly or a semi-monthly variation related to moon phase. There is reason to believe that this is related to the moon through some mediator other than the ocean tides or nocturnal illumination.

7. The compass-directional response to a rotating 5-gauss horizontal magnetic field, shows a monthly variation or a semi-monthly one. Whether it is monthly or semi-monthly, and its amplitude, appear to vary parallelly with comparable cycles obtained during the same period in response to equivalent changes in orientation in the earth's 0.17-gauss field. This gives additional support to the conclusion that geomagnetism plays an important role in these orientational phenomena of the snails.






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Copyright © 1964 by the Marine Biological Laboratory.