Phylum Mollusca -Most are marine.

-Soft-bodied animals, but most are protected by a hard shell made of calcium carbonate.

-The body has three main parts:

1. A muscular foot used for movement

2. A visceral mass containing most of the internal organs

3. A mantle (a heavy fold of tissue that drapes over the internal organs)

Some examples of this phylum include:

The Bivalves- These include the clams, oysters, and mussels. These organisms have shells divided into two halves that are hinged in one spot. They are held tightly together by powerful muscles to protect the soft-bodied animal. Bivalves also use gills for feeding, as well as gas exchange. They trap fine food particles in mucus that coats the gills, then use cilia (tiny hairs) to move the particles towards their mouth. Animals which feed in this way are known as suspension feeders.

At the moment, mussels are becoming an important part of the aquaculture industry due to their suspension-feeding capabilities.

Mussels Feeding on Particulates in the Water

The mussels used at the salmon sites are collected from the wild. At times, they are power sprayed off of other salmon site piping where they tend to grow naturally. The mussels are placed into large containers and then sorted because uniformity is needed in the size of the mussels for the project.

Mussels being measured….

Photos taken by Gregor Reid

The chosen mussels are then placed inside of “socks” made of cotton and are attached to the salmon cages where they will eat the particulates floating in the water. As well, mussels are being studied closely because it is thought that they will also eat the disease known as ISA off of the salmon.

Mussel socks hanging from the salmon cage.

Taken by Gregor Reid

A diver is inspecting more mussel socks.

Taken by Gregor Reid.

In addition, the mussels grow well at these aquaculture sites and can be sold for revenue, in addition to the salmon.

Full Mussel Sock

Photos taken by Gregor Reid

Kelp, which is not a mollusc, but a plant, is also added to the salmon site environment. It is very beneficial to the farming process because it helps to absorb the ammonia which the salmon deposit into the water. This kelp is not collected in the wild. Instead, it is grown in a lab setting on a string using very small kelp plants. If the kelp is left to grow at the salmon site over the summer, it will end up being harvested for use in fertilizers. Most of the time, the kelp is grown at the site over the winter months (November to May), and harvested early for high quality purposes. This kelp is sent to places such as Asia for such things as food garnishes.

Taken by Gregor Reid

Amazingly, polychaetes are added to the aquaculture world. They are placed under the cages at the sea bottom to feed on the waste feed and salmon feces that drops to the ocean floor. Even they can be profitable if sold as live sea bait.

Photos taken by Gregor Reid.

Other examples of mollusks include:

1. The Gastropods - Most gastropods are protected by a single, spiraled shell into which the animal can hide. Many of these organisms have heads with eyes at the tips of the tentacles. In terms of locomotion, they are not very speedy. They inch along by a rippling motion of their elongated foot. Examples of these animals include the snail and the slug.

Taken by Catriona Day

Taken by Allan Hennigar2.The Cephalopods

The cephalopods include the squid, octopus, and the nautilus. These animals are built for speed, which fits their carnivorous diet. They have beaklike jaws to bite their prey, and they can inject poison to immobilize the victim.

Other characteristics of cephalopods include:

1. a reduced, and internal shell (squid) which acts as a support the soft, muscular body, or a shell that is missing altogether (octopus).

2. a well developed nervous system with a complex brain, and have the ability to learn.

3. well developed sense organs. Their eye structure is similar to that of the vertebrates, but only the Sparkling Enope Squid of the West Pacific has been proven to see in colour. Their eyes are sensitive to brightness, size, and shape.

The Sparkling Enope Squid

4. having tentacles which are a modification of the mollusc foot.

5. being able to live only in marine or brackish water habitats.

6. having special skin cells called chromatophores which can change colour for use as camouflage and / or communication.

See clip on camouflaged octopus at

http://ca.youtube.com/watch?v=GRSbC6HAgNE

See preserved Short Finned Squid – pass it around, and give a bit of info on it (teacher’s guide).