A variety of animals use Earth's magnetic field as a reference for their orientation behaviour. Although distinctive magnetoreception mechanisms have been postulated for many migrating or homing animals, the molecular mechanisms are still undefined. In this study, we found that zebrafish, a model organism suitable for genetic manipulation, responded to a magnetic field as weak as the geomagnetic field. Without any training, zebrafish were individually released into a circular arena that was placed in an artificial geomagnetic field, and their preferred magnetic directions were recorded. Individuals from five out of the seven zebrafish groups studied, groups mostly comprised of the offspring of predetermined pairs, showed bidirectional orientation with group-specific preferences regardless of close kinships. The preferred directions did not seem to depend on gender, age or surrounding environmental factors, implying that directional preference was genetically defined. The present findings may facilitate future study on the molecular mechanisms underlying magnetoreception.

We have demonstrated interface-treated Josephson junctions without deposited barriers in a trilayer structure. In the junctions, barriers were formed through an etching process and an annealing process for base YBa2Cu3O7-x (YBCO) films. The junctions showed resistively-shunted-junction-type characteristics over the entire temperature range below 70 K. A magnetic field modulation of more than 80% was observed throughout the operating temperature range. The obtained I c R n product was 2.1 mV at 4.2 K. The 1σ spreads in the junction parameters of 10% or better were observed for eight out of nine junctions in a chip.

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