Magnetic sense in the Japanese eel, Anguilla japonica, as determined by conditioning and electrocardiography

Abstract

Magnetosensitivity of the Japanese eel, Anguilla japonica, was examined by conditioning and electrocardiography. Marine eels, river eels and farmed eels were conditioned to an imposed magnetic field ranging from 12·663·nT to 192·473·nT parallel to the fish body, which was placed along the earth's west-east axis. Electrocardiograms were recorded with electrodes placed close to the fish body inside a PVC pipe shelter. After 10-40 conditioning runs, all the eels exhibited a significant conditioned response (i.e. slowing of the heart beat) to a 192·473·nT magnetic field and even to a 12·663·nT magnetic field, respectively equivalent to 5.92ϫ and 0.38ϫ the horizontal geomagnetic field (32·524·nT) at our laboratory. The west-east vector of the imposed magnetic field (12·663·nT) combined with that of the geomagnetic field and produced a horizontal resultant magnetic field of 21°easterly. Therefore, Japanese eel are magnetosensitive whether they are at sea, in the river or in the farm. Results of the present study were compared with those of past studies that showed no magnetic sense in the American eel, Anguilla rostrata, and the European eel, Anguilla anguilla.

Orientation and Navigation in Vertebrates

“…Application of electrocardiography methods and behavioral conditioning has shown sensitivity to magnetic fields in the fry and larvae of brook trout, Salmo trutta , and the adult and glass eel (the newly metamorphosed juveniles) stages of Japanese eels, Anguilla japonica (Nishi et al 2004;. Interestingly, anosmic Japanese eels were not able to detect magnetic field , which rather suggests a magnetite-based magnetoreceptor located in the nasal cavity or near it, and is in accord with the previous histological findings yet mentioned.…”

Spawning Sites of the Japanese Eel in Relation to Oceanographic Structure and the West Mariana Ridge

“…There is no evidence that these eels have reached their spawning areas though, so their behaviors might drastically change once they reach the spawning area to include more movements into depths closer to the surface where they could find some aspect of the low salinity water mass, or its absence. Japanese eels and other anguillids are known to have a geomagnetic sense [32], [56], [57] that might be used to help find their spawning areas, but there has also been speculation that they might use various types of odors associated with fronts or different water masses, or pheromones from each other, to locate their spawning sites and to find mates [31], [51], [52]. However, it is essentially still a mystery how the eels reach their spawning areas and find mates for spawning.…”

Ecology of Anguilliform Leptocephali: Remarkable Transparent Fish Larvae of the Ocean Surface Layer

“…However, since anguillid glass eels, and yellow eels have been found to have a geomagnetic sense (Nishi et al 2004;Nishi and Kawamura 2005), the function of which is most likely to guide migrating adult eels back to their spawning area (see Tsukamoto 2009) using a geomagnetic map sense as hypothesized for other marine animals (Lohmann et al 2008). If true, this would require that leptocephali also have the ability to imprint on the geomagnetic cues that characterize the area where they were born.…”