Dancing sea turtles reveal how animals navigate magnetic fields for migration over thousands of kilometers and to find food

Amazing stuff!

"... But a new study has presented the first evidence that loggerhead turtles (Caretta caretta) use magnetic fields as a compass to determine direction and also use it to determine their geographical location.

There’s a little dance involved, too.

Sea turtles are extraordinary navigators, able to trace unseen pathways across thousands of kilometres of the ocean and return to the same feeding sites migration after migration. ..."

"...  sea turtles returning to the same feeding sites again and again throughout their lifetimes — despite traveling up to 10,000 miles across the planet. ... hypothesized that these turtles used Earth’s magnetic field to memorize specific geographic areas that they associated with food ...

team conditioned loggerhead turtles to magnetic fields replicating those that exist in various oceanic locations, repeatedly feeding the turtles in some magnetic fields while not feeding them in others. When later exposed to the fields in which they were fed, the turtles exhibited “turtle dancing behavior,” indicating that they associated that specific magnetic signature with food. ..."

From the abstract:

"Growing evidence indicates that migratory animals exploit the magnetic field of the Earth for navigation, both as a compass to determine direction and as a map to determine geographical position. It has long been proposed that, to navigate using a magnetic map, animals must learn the magnetic coordinates of the destination, yet the pivotal hypothesis that animals can learn magnetic signatures of geographical areas has, to our knowledge, yet to be tested.

Here we report that an iconic navigating species, the loggerhead turtle (Caretta caretta), can learn such information. When fed repeatedly in magnetic fields replicating those that exist in particular oceanic locations, juvenile turtles learned to distinguish magnetic fields in which they encountered food from magnetic fields that exist elsewhere, an ability that might underlie foraging site fidelity. Conditioned responses in this new magnetic map assay were unaffected by radiofrequency oscillating magnetic fields, a treatment expected to disrupt radical-pair-based chemical magnetoreception, suggesting that the magnetic map sense of the turtle does not rely on this mechanism.

By contrast, orientation behaviour that required use of the magnetic compass was disrupted by radiofrequency oscillating magnetic fields. The findings provide evidence that two different mechanisms of magnetoreception underlie the magnetic map and magnetic compass in sea turtles."

Dancing turtles reveal how animals navigate magnetic fields

Dancing turtles unlock scientific discovery (original news release)

Learned magnetic map cues and two mechanisms of magnetoreception in turtles (no public access)

Magnetic crystals found in the noses of salmon could aid navigation

Amazing stuff!

"... Salmon hatch in rivers, where they spend a year or so before migrating to the sea – returning as adults to their riverbed of birth to spawn. This migration can extend over thousands of kilometres ... 
The team discovered that magnetite within the salmon [nose] cells exists in compact, egg-shaped clusters. Each of these clusters measures around 200–300 nm in diameter, and contains roughly 100–200 individual crystals.

The growth of crystals inside living cells is called biomineralization, which is used by magnetotactic bacteria to grow chains of magnetite crystals. The bacteria use these tiny “compass needles” to orient themselves with respect to Earth’s magnetic field, possibly to move to regions of optimal oxygen content.
Through subsequent genetic analysis, ... team discovered that the biomineralization genes expressed in salmon receptor cells were like those found in bacteria containing magnetite. This ... suggests that several billion years ago a magnetite-containing bacteria may have been incorporated into a more complex organism in a process called endosymbiosis – creating a distant ancestor of the salmon. ..."

From the abstract:

"Animals use geomagnetic fields for navigational cues, yet the sensory mechanism underlying magnetic perception remains poorly understood. ... Here, we discover that salmonid olfactory epithelium contains magnetite crystals arranged in compact clusters and determine that genes differentially expressed in magnetic olfactory cells, contrasted to nonmagnetic olfactory cells, share ancestry with an ancient prokaryote magnetite biomineralization system, consistent with exaptation for use in eukaryotic magnetoreception. We also show that 11 prokaryote biomineralization genes are universally present among a diverse set of eukaryote taxa and that nine of those genes are present within the Asgard clade of archaea Lokiarchaeota that affiliates with eukaryotes in phylogenomic analysis.  ..."

Magnetic crystals found in the noses of salmon could aid navigation – Physics World

Conservation of magnetite biomineralization genes in all domains of life and implications for magnetic sensing (open access)

Salmons Come With Magnetic Sensors

Trigger

Just read “Navigation im TierreichLachse mit magnetischer Seekarte” dated 3/12/14. Here is the abstract of the English language article.

Finally, scientists discovered a magnetic sense in salmon. Apparently some kind of map is inherited by the offspring of salmon.

Excerpts from abstract (emphasis added):

“A particular challenge is explaining how juvenile animals with no prior migratory experience are able to locate specific oceanic feeding habitats that are hundreds or thousands of kilometers from their natal sites”

“We further show that fish use the combination of magnetic intensity and inclination angle to assess their geographic location. The “magnetic map” of salmon appears to be inherited, as the fish had no prior migratory experience.”

What About Humans?

Are we really without such a sense or have we just not discovered it? Has it been dormant?