serves such a function. The presence of an electrosensing mechanism is common among oceanic fish
and the suggestion has been made that this capability was related to the direction-sensing associated
with their migratory behavior, either by directly sensing the earth's electric field or by sensing the
currents and voltages generated by the movement of water currents (e.g., the Gulf Stream) through the
earth's magnetic field.
The American eel is one such migratory species, hatching out of eggs laid in the fresh water
streams of the eastern seaboard and migrating as small larval "elvers" about one inch long out to the
open ocean. Ultimately they travel to the Sargasso Sea, navigating with precision over a thousand miles
of open ocean. In the Sargasso Sea the elvers grow to adults and when sexually mature they reverse the
pathway, traveling back to the same streams they were hatched in to mate. In 1972 Rommell and
McCleave studied the sensitivity of these animals to electrostatic fields using a conditioned reflex
experimental format (28). The animals displayed a sensitivity to DC fields of 0.67 µV/cm and 0.167 x
10-2 ,µamp/cm2, values well within those generated by water currents flowing through the earth's
magnetic field. The eels were found to be sensitive to these electrical parameters only when the field
was oriented parallel to the long axis of the animal; fields perpendicular to the long axis were not
sensed. As Rommell and McCleave point out, if one assumes the ability to distinguish polarity, the
animals had only to orient themselves to optimize the signal of the appropriate polarity and they could
migrate in both directions (to and from the Sargasso Sea) with ease.
From all the foregoing reports it is obvious that the present normal earth magnetic field is an
important parameter of the environment for living things. Changes in the fields in the past have been
shown to exert evolutionary pressure and possibly even to have been associated with biogenesis. All
living things are at present intimately tied to various aspects of the earth's field, and it seems quite
possible that even more dramatic findings will be reported in the future. It must be kept in mind that the
relationship is a subtle one, in contrast to the more obvious parameters of the environment. Since the
present relationship between living things and the electromagnetic environment is the result of several
billions of years of development, the question of the biological effects of abnormal electromagnetic
parameters introduced into the environment by man's activities becomes of some importance.
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ELECTROMAGNETISM & LIFE - 56