Otolith extraction

Method

Material

• Scalpel with a blade n° 24
• Distilled water
• Steam room
• 3 plastic containers (bath 1, bath 2, bath 3)
• Plastic tweezers (tweezers 1 ; tweezers 2 ; tweezers 3)
• Optic paper
• W iping paper for optic
• Watch glass
• Micro-tubes type « ependorf » that can be previously cleaned with nitric acid and rinsed with distilled water, and dried.
• Colored paper
• Nitric acid 10 %
  

Technic

The otolith chosen for eels age reading is the sagittae which is the biggest otolith for this species. The extraction of sagittae otoliths is described from sectioned eels heads. The heads are processed fresh or frozen while they are still hard.

The method described for otolith extraction is a transversal section of the head.

A transversal section of the head is performed at the posterior part of the crane.

Looking behind the anterior part of the section, the posterior part of the brain appears.
The two cavities of the inner ear are then displayed on both sides of the rachidian bulb [Panfili, 2002].

1. Extract the otolith with a pair of plastic tweezers.

2. Rinse the otolith in three successive baths of distilled water, remove the tissue and endolymph on the otoliths.

3. Leave the otoliths to dry in the steam room.

4. Store the otoliths in a dry microtube marked with the reference of the sample.

5. Renew the water of the baths for each eel.