V. V. Krylov

Magnetic Fields and Fish Behavior

The available data on the effect of natural and artificial magnetic fields on fish behavior are considered. In this aspect, Elasmobranchii and Teleostei are studied more thoroughly. Elasmobranches and some teleosts are able to perceive magnetic fields via electroreceptors. Some teleosts can sense magnetic fields via sensory cells that contain crystals of biogenic magnetite. Laboratory and field studies demonstrate that magnetic fields affect fish locomotor activity and spatial distribution. The geomagnetic field can be used by fish for navigation. In addition, the effect of artificial magnetic fields and natural fluctuations of the geomagnetic field on fish embryos lead to changes in their development. It is suggested that changes in development can have an aftereffect on fish behavior.

Effects of an induced magnetic storm on the early ontogenesis of roach Rutilus rutilus (L.)

The influence that an induced magnetic storm (IMS) modeled in a confined volume has on the early ontogenesis of Rutilus rutilus was studied. The significant effects of the IMS were observed for the hatching rate of roach embryos, the size-weight and morphometric parameters of the fry, the variability of the vertebral column, and ontogeny stability in the roach offspring.

Effect of a magnetic field and copper upon activity of hydrolytic enzymes in roach (Rutilus rutilus) underyearlings

Remote effects of separate and combined exposure to copper (0.001 mg/L and 0.01 mg/L) and a low-frequency magnetic field during early embryogenesis in roach (Rutilus rutilus) underyearlings were studied. The study revealed that exposures lead to changes in the linear and weight parameters, activity of glycosidases, and kinetic characteristics of carbohydrates hydrolysis in the fish intestine. Copper decreases the activity of glycosidases and modifies the effect of a magnetic field. The exposure-induced decrease in the value of the seeming Michaelis constant of carbohydrate hydrolysis indicates the increase in the enzyme-substrate affinity. This phenomenon may be attributed to the adaptive reactions in response to negative effects of copper and a magnetic field during early ontogenesis in roach.

Delayed consequences of extremely low-frequency magnetic fields and the influence of adverse environmental conditions on roach Rutilus rutilus embryos

This study presents data collected over a 6 year period on the effects of extremely low-frequency magnetic fields (MFs) (1.4-1.6 µT, 500 Hz and 1.4-1.6 µT, 72.5 Hz) and MFs in combination with other environmental stressors (elevated temperature, 0.01 mg l(-1) trichlorfon, 0.01 mg l(-1) copper sulphate pentahydrate) on roach Rutilus rutilus embryos. Effects were studied during different stages of early development. Rutilus rutilus were raised in ponds for 4 months after exposure to MFs. The mass, standard length (LS ) and morphological characteristics of underyearlings which were exposed as embryos were recorded. An increase in embryo mortality and a decrease in LS and mass indices in underyearlings were noted after they had been exposed to a combination of MFs and different adverse environmental factors. In addition, exposure to MFs led to changes in the total number of vertebrae and the number of seismosensory system openings in the mandibular bones of underyearlings. MFs of different frequency caused both increases (500 Hz) and decreases (72.5 Hz) in morphological diversity. The stressors used in this study, however, did not increase the fluctuating asymmetry of bilateral morphological characteristics. The possible microevolutionary effects of exposure to MFs alone and in combination with other adverse environmental factors upon natural fish populations are discussed.

The effect of a typical magnetic storm on mitosis in the embryo cells and the length and weight of roach (Rutilus rutilus L.) prolarvae

The action of the tested variants of a typical magnetic storm (MS) has a biological effect on cellular and organismal levels in the prolarva stage. The impact of this environmental factor leads to increased mitotic activity in blastocysts, it can trigger the early hatching of embryos, and it has no negative impact on the size-weight characteristics of free embryos.

Impact of simulated geomagnetic storm on activity of digestive glycosidases in roach Rutilus rutilus underyearlings

Long-term consequences of simulated geomagnetic storm action on early stages (0–24 h, 24–48 h, 48–72 h and 72–96 h post fertilization) of roach Rutilus rutilus embryogenesis were studied. The study revealed that fluctuations of magnetic field resulted in the decrease in the fish body length and weight, as well as in the differently directed changes in the activities of glycosidases (maltase, sucrase, and amylolytic activity) and kinetic characteristics of carbohydrates hydrolysis in the intestine of 4 month-old roach. The most pronounced changes in the fish body sizes were noted after exposure to magnetic field fluctuations within the time period of 48–72 h post fertilization. Relatively low values of Michaelis constant were revealed in the fish developed during embryonic stage either in the hypomagnetic conditions or under impact of simulated geomagnetic storm. This phenomenon may be considered as a response of fish digestive system to changes in the magnetic field during embryogenesis.

Impact of alternating electromagnetic field of ultralow and low frequencies upon survival, development, and production parameters in Daphnia magna straus (Crustacea, Cladocera)

The impact of alternating magnetic field (AMF) of ultralow and low frequencies during a sevenday-long exposure on Daphnia magna Straus was studied. It is shown that AMF may decrease the survival and the time it takes to reach sexual maturity. AMF with a frequency of 500 Hz has the most pronounced negative impact upon survival and maturation. AMF of 50 Hz accelerates maturation. In a chronic experiment at 500 Hz, the share of vital offspring increased, while the sizes of newborns decreased in parent specimens that matured under the impact of a magnetic field. The action of a 500 Hz AMF on daphnias before littering of offspring leads to an increase in the number of newborns in the reproductive period.

Exploratory behavior of juvenile roach Rutilus rutilus (L.) (Teleostei: Cyprinidae) in a maze after different magnetic impacts on embryos

We have investigated a sequence of visits to arms in a cross maze in juvenile (1-year-old) roach Rutilus rutilus (L.). Fish embryos of one group are raised under a natural geomagnetic field. The embryos of another group are exposed to the main phase of a simulated geomagnetic storm (changes in geomagnetic field up to 100 nT for each component). It turns out that the sequence of visits does not differ from random in both groups. Thus, the exploratory behavior in juvenile roach differs from other animal taxa investigated earlier. In the latter taxa a spontaneous alternation was observed: a tendency to visit the arm which was visited least recently.

Blastomere mitosis, hatching, survival rate, and size parameters of prolarvae in the roach Rutilus rutilus following exposure of eggs and sperm to main phase of a strong magnetic storm

Eggs and sperm obtained from breeder roaches Rutilus rutilus were exposed, prior to activation with water, for 25 minutes to the main phase of a strong magnetic storm. Such exposure increased the proportion of stages completing mitosis during the cleavage of blastomeres and an increase in the variation of the mitotic index. No changes in the frequency of chromosome aberrations were revealed in experimental embryonic cells compared to control cells. The rate of hatching, survival of embryos, and size and mass parameters of prolarvae varied in experimental and control samples, but no link of this variation with exposure to a magnetic storm has been established.

Orientational behavior of animals with the geomagnetic field and mechanisms of magnetoreception

Contemporary data on the orientation and navigation of animals from different taxa with the geomagnetic field are considered in the review. The mechanisms of magnetoreception in animals are described. In this regard, several taxa of fishes are able to perceive the magnetic field via electroreceptors. Some animals can sense changes in the magnetic field polarity via sensory cells containing iron compounds. In addition, animals from different taxa are able to perceive the inclination of the magnetic field via a change in singlet and triplet yields of radical-pair reactions under the influence of the magnetic field. In the latter case, the molecules of cryptochrome can play a crucial role. It is considered that the cryptochrome excited by shortwave light can produce long-living radical pairs affected by the geomagnetic field.