Kalmijn Adrianus J.

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Kalmijn
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Adrianus J.
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  • Technical Report
    Statistical mechanics of geomagnetic orientation in sediment bacteria
    (Woods Hole Oceanographic Institution, 1981-04) Gilson, Michael ; Kalmijn, Adrianus J.
    Last year we reported on time-of-transit experiments in which magnetically orienting bacteria crossed a 1-mm stretch in the direction of a uniform magnetic field. The bacteria were found to behave as tiny self-propelled compass needles subject both to magnetic field alignment and to the randomizing effect of thermal agitation. In strong fields, magnetic bacteria are held in tight aligment; in weaker fields, their swimming paths meander more and transit times are greater. Paul Langevin derived an expression for the distribution of orientation in an ensemble of free-moving dipole particles as a function of ambient field strength. His theory becomes applicable to our experiments when bacterial migration is analyzed as a sequence of short steps during each of which the cell swims in a direction randomly selected from the Langevin distribution . The duration of each step, Δt, is actually a time constant of the cell's loss of directionality due to thermal agitation. By thus treating the migration as a process of random walk with drift, we are able to predict the mean and variance of the time of transit across a 1-mm stretch.
  • Technical Report
    Field experiments on electrically evoked feeding responses in the dogfish shark, Mustelus canis
    (Woods Hole Oceanographic Institution, 1981-05) Dawson, Benjamin G. ; Heyer, Gail W. ; Eppi, Rene E. ; Kalmijn, Adrianus J.
    From previous experiments, we learned that sharks, skates and rays have an electric sense that enables them to detect voltage gradients as low as 0.01 µV/cm within the frequency range from DC up to 8 Hz. The animals use their electric sense in predation, cuing in on the bioelectric fields commonly produced by fish and aquatic invertebrates. To quantify the response, we analyzed the feeding behavior of the shark Mustelus canis in Vineyard Sound off Cape Cod, Mass. An electrode panel was embedded in the ocean substrate in a water depth of 2-3m. Two salt-bridge electrodes, simulating a small prey fish, were placed 2 em apart at a distance of 15 cm from a centrally located odor source. Another pair of salt-bridge electrodes, simulating a larger fish, were placed 5 em apart at a distance of 30 cm on the other side of the odor source. DC current of 8 µA was applied to either one or both pairs of electrodes. Observations were made at night from a Boston Whaler with a glass bottomed observation well. Liquefied herring chum attracted and motivated sharks. In sum, the results support the conclusion that these sharks, once motivated by odor rely heavily upon their keen electric sense in executing their final strikes.
  • Technical Report
    Migration rate of mud bacteria as a function of magnetic field strength
    (Woods Hole Oceanographic Institution, 1980-11) Teague, Barbara D. ; Gilson, Michael ; Kalmijn, Adrianus J.
    Certain marine and freshwater mud bacteria are endowed with a permanent magnetic dipole moment. This moment is attributed to an endogenous chain of tightly coupled, single-domain magnetite crystals. When separated from the mud, these magnetic bacteria swim north, following the earth's magnetic field lines. As at Woods Hole, Massachusetts, the field lines are steeply vertically inclined, the bacteria rapidly return to the bottom substrate where they seem to thrive best. To quantify this migration, we measure the time to traverse the distance between two lines, 1 mm apart, as a function of the ambient magnetic field strength. Using dark-field illumination, we observe single organisms as they migrate in a low-oxygen hemocytometer chamber. We control the ambient magnetic field by regulating the current through a Helmholtz-coil system. At high magnetic field strengths, the bacteria follow a virtually straight path, swimming at rates around 150 µm/sec. At lower field strengths, they take a more random path which reduces their migration rate. Although they swerve moderately at the earth's magnetic field strength (0.5 gauss) , the bacteria still achieve about 80% of their maximum migration rate observed at higher-gauss fields. This suggests that the bacterial dipole moments are well adapted to orientation in the earth's magnetic field. Since the strength of their magnet determines the degree to which the organisms overcome random motion, we can estimate the magnitude of their dipole moment.
  • Technical Report
    Experimental evidence of geomagnetic orientation in elasmobranch fishes
    (Woods Hole Oceanographic Institution, 1979-03) Kalmijn, Adrianus J.
    Marine sharks, skates, and rays are endowed with an electric sense that enables them to detect voltage gradients as low as 0.01 μV/cm within the frequency range of direct current (DC) up to about 8 Hz. Their electroreceptor system comprises the ampullae of Lorenzini, which are delicate sensory structures in the snouts of these elasmobranch fishes. Sharks, skates, and rays use their electric sense in predation, sharply cueing in on the DC and low-frequency bioelectric fields of their prey. Swimming through the earth's magnetic field, they also induce electric fields that may provide them with the physical basis of an electromagnetic compass sense. Their ability to orient magnetically has in fact been demonstrated in recent training experiments.