Magnetic compass orientation in the European eel

Area of Science:

• Animal behavior
• Neuroethology
• Sensory biology

Background:

• European eels undertake extensive migrations from Europe to the Sargasso Sea.
• The precise migratory routes and orientation mechanisms of European eels remain largely unknown.
• Previous studies have not conclusively demonstrated magnetoreception in European eels at earth-strength magnetic field levels.

Purpose of the Study:

• To investigate the existence and function of a magnetic compass in European eels.
• To determine how magnetic field orientation is affected by temperature and prior experience.
• To understand the adaptive significance of magnetic orientation for eel migration.

Main Methods:

• Eels were tested in controlled conditions with altered magnetic fields (North, South, East, West).
• Orientation behaviors were observed in relation to magnetic North and prior displacement direction.
• Experiments were conducted at different temperatures (below 12°C and 12-17°C).

Main Results:

• Eel orientation was influenced by the tank in which they were housed before testing.
• At lower temperatures, eels oriented relative to magnetic North based on their displacement direction.
• At higher temperatures, eels exhibited orientation perpendicular to their displacement axis, suggesting temperature-dependent strategies.

Conclusions:

• European eels possess a magnetic compass sense.
• Eels utilize this magnetic compass to orient themselves based on recently registered directions.
• This ability is crucial for successful navigation and reorientation during their long-distance seaward migrations.