Disection+of+the+mussel


 * MUSSEL DISSECTION**


 * Objective:**

.- To study the external and internal anatomy of a mussel.


 * Material: **

.- Scissors .- Mussels (the mussels must be opened with stream the previous night) .- Dissecting tray


 * Background: **

Mussel is a bivalve mollusc. As the term bivalve indicates, these animals have a shell made of two valves, which are similar in shape and size and are hinged on one side.

 Most molluscs share four characteristic features:
 * .- Head **
 * .- Body mass with the main organs **
 * .- Muscular foot to move about **


 * External anatomy **

Determine the dorsal, ventral, anterior and posterior regions of the animal (see the drawings).

The valves are held together by two strong **adductor muscles** inside the shell.

.- On the outer side of each valve you will observe several lines, they are **growth lines.**

.- On the ventral side obseve **the filaments** to attach the animal to a substrate.

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">.- The **pearl** (nácar) is the bright substance that covers the interior of the shell.


 * <span style="font-family: 'Times New Roman',serif; font-size: 14pt;">Internal anatomy **

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">The animal has a soft body without any segments and without a differentiated head.

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">As these animals have **bilateral symmetry**, all their organs are located like the pages of a book.

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">The **mantle**, two lobes that cover the whole body of the animal, the border is black.

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">By transparency we can observe a greenish organ which contains the **pancreas** and the **live**r.

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">As you lift the mantle, you will observe on its inner surface a two pleated structure, gray or brown colored, which are the **gills (they are like sheets).**

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">Locate the **mouth**, surrounded by **four tongue-shaped structures.**

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">Locate the black **foot** and, next to it, the **filaments gland** and the **gonads**. Gonads are yellowish in females and orange in males.

<span style="font-family: 'Times New Roman',serif; font-size: 14pt;">.- Take a sample of the gills, place it on a slide. Add a cover slip and observe it under the microscope.