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Bioelectromagnetism

FIGURE 3.9 Behavioral responses of organisms to electromagnetic felds in the aquatic environment. (a)

Behavior of a shark near a dipole imitating prey buried in the sand. (b) Sharks in a situation like a tidal current with

the geomagnetic feld. Electric feld induction in fsh-oriented upstream and downstream in the fow is shown. (c)

Sharks swimming in geomagnetic feld. (d) As magnetic bacteria are anaerobic, movement is toward the bottom,

where conditions are most anaerobic, as directed by geomagnetic feld. (From Kalmijn, 2000.)

intensively all over the bottom of the pool, but did not notice the plaice any longer, although they ofen

passed it very closely. Kalmijn proved directly that the sharks and rays are actually able to detect the

source of such an electric feld as produced by the plaice. (5) By stimulating the bioelectric felds of the

plaice with a direct current of 4 μA, apparently natural feeding responses could be elicited. (6) Sharks

and rays swam just over the piece of whiting to reach the site of the electrodes; ofen they swam away,

afer digging at the electrodes, without fnding the piece of whiting. Kalmijn commented further that

the electric felds acted as a much stronger directive force or the sharks and rays than did the visual and

chemical stimuli of the piece of whiting (1971).

3.6.2 Magnetoreception

Te electrophysiological in vitro responses to magnetic stimulation were reported from the pineal

gland. Semm and his co-worker provided the frst evidence that the cells in the pineal gland can

respond to stimuli other than light (1980). Tese researchers demonstrated a signifcant diminution of

in vivo electrical activity of single pinealocytes of guinea pig following acute inversion of the vertical

component of the geomagnetic feld by means of a Helmholtz coil. Tis fnding suggested that pineal

melatonin synthesis might be afected by magnetic felds. Welker demonstrated that rats exposed to a

15-minutes inversion of the horizontal component of the geomagnetic feld during the nighttime hours