A Winnicki

REACTIONS OF FISH EMBRYOS AND LARVAE TO CONSTANT MAGNETIC FIELDS

Abstract Constant magnetic field of low value slows down the embryonic development of trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss). Hatchlings were longer and heavier, and also more motile than those in the control experiment. Magnetic field induces a change in the circulation motion in embryos and larvae of pike (Esox lucius) and carp (Cyprinus carpio), and in the embryos of trout (5. tnitta). Exposure to magnetic field in embryos causes an increase in a heart rhythm, particularly during the early pulsation period of the forming heart. Magnetic fields cause a change in the gas exchange in embryos of a rainbow trout (O. mykiss). Intensity of breathing processes increase in a magnetic field, however, is dependent on stage of embryonic development, and it is especially manifested in the period of an advanced organogenesis. Embryos of rainbow trout (O. mykiss) and trout (S. tnttta) exhibit a sense of direction both in natural and artificially created magnetic field.

The effect of magnetic field on permeability of egg shells of salmonid fishes

The embryos of fishes during their development, between the egg activation and their hatching, are exposed to action of various factors of the external environment. Those factors, while acting simultaneously, may exert higher pressure, than when acting individually. Despite the common assumption about alleged stability of the aquatic environment, its biotic and abiotic factors, affecting aquatic organisms, may be highly diversified. An individual organism is not only affected by selected, uniform environmental factors. Usually the maintenance of homeostasis is dependant on a complex system of a number of external and internal stimuli (Haas et al. 1997) The magnetic field, and the associated magnetic phenomena are so ubiquitous that they have hitherto been neglected. They attracted some more attention in recent decades and it become evident that living organisms are not indifferent for the action of the magnetic field (Wiltschko and Wiltschko 1995, Kirschvink 1997). The natural magnetic field of the earth is an integral component of the environment, in the same extent as temperature or gravitation, and it also constitutes the background for life processes on the Earth. The common nature of the magnetic field has prompted many researchers to study in detail its action on living organisms. Wadas (1978) distinguished three basic reasons why magnetic fields affect living organisms: 1) action of non-compensated electron spins, 2) action on liquid crystals, 3) effect on positiveand negative charges, being in motion. To answer the question of the action of the magnetic field on animals, many researchers observed effects of such action. Among the aspects studied was the homing ability of insects (honey bee) (Gould 1980), crustaceans (lobster)(Boles and Lohmann 2003), fishes (salmonids)(Quinn and Brannon 1982), amphibians (newt)(Phillips 1986), reptiles (turtles)(Lohmann et al. 1999), or birds (pidgeon)(Keeton 1971). The behavioral experiments focused mainly on species performing long-distance migrations, such as eels and salmonid fishes, as well as elasmobranch fishes (Mayer et al. 2005, Nishi et al. 2005). ACTA ICHTHYOLOGICA ET PISCATORIA (2007) 37 (2): 129–135 DOI: 10.3750/AIP2007.37.2.10