Mollusks

mollusks
Introduction:
Welcome to Module 6 dear AGRIB109_A students! This sixth and last

module will provide us understanding and appreciation of the other
aquatic species aside from the fish.
It will present crustaceans, mollusks and seaweeds and the many ways
by which these aquatic species live and can be made productive and
lucrative in the market.
There are indeed more than meets the eye when it comes to aquaculture
so there are myriads of profitable opportunities await each one in the
fisheries industry. This reality will be given even more light and
motivation.
It is my continued hope that you ceaselessly have fun and sustained

interest while we actively course through this final stage in our study and
even beyond.
Learning Objectives:
1. Identify the other aquatic species in

aquaculture.
2. Translate learning to increased opportunities
and productivity in the field of fisheries.
3. Create a workable concept around the
knowledge acquired in this module.
Byssus-attachment
Yellow-orange color-female
White -male
Biofilters-strain the water

Class Common Description of Shell Examples
Name
Gastropoda Gastropods Shell-less Aplacophora,

Or single shelled Pond snails, land
slugs, sea
butterflies, sea
hares, nudibranches
Bivalvia Bivalves Two shells that are Clams, oysters,
held together by scallops, mussels
one or two powerful
muscles
Cephalopoda cephalopod Only small internal Octopi, squids,

shells or no shells cuttlefishes,
nautiluses
Form and Function in
Mollusks
Four parts of the body plan of most mollusks
◦ Foot Short flat movable muscular organ located on the ventral surface;
it allows the snail to move or to attach itself to a support using elastic
filaments.
◦ Shell Calcareous casing produced by the mantle; it has three layers and
protects the main organs of the mollusk.
◦ Mantle Thick fold of tissue forming two lateral lobes; it envelops the
organic mass of the mollusk and secretes its shell, produce the calcium
salts.
◦ Visceral mass contained within the shell; it generally holds the

bulk of the digestive, reproductive, excretory, and respiratory
systems.
ligament
Corneous structure located behind the umbones and joining
both valves of the shell; its elasticity allows them to pull apart.
umbo
Protuberance at the terminal end of the valve, from which the
shell grows.
intestine
Section of the digestive tract between the stomach and the anus
where absorption of nutrients is carried out and waste is
transformed into fecal matter.
anus
Terminal orifice of the digestive tract enabling ejection of fecal
matter.
gonad
Genital gland producing spermatozoa (sperm) or ova (eggs),
depending on the sex of the mollusk.
gills
Respiratory organs located between the foot and the mantle,
formed of two layers of ciliated filaments, which filter water and
retain food particles.
Trochopore is a larval stage of a mollusk.
Mollusk foot are flat structures for crawling,

spade shaped, structures for burrowing,
and tentacles for capturing prey
Mollusk shell is made by glands in the

mantle that secrete calcium carbonate.
Snails and slugs feed using a tongue-shaped
structure known as radula.
A siphon is a tubelike structure through which water

enters and leaves the body.
Land snails and slugs typically live only in moist

places.
They respire using a mantle cavity that has a large

surface area lined with blood vessels, and the lining
must be kept moist so that oxygen can diffuse
across its surface.
 How does an open circulatory system
carry blood to all parts of a mollusk’s
body?
 Blood is pumped through vessels by a

simple heart. Blood eventually leaves
the vessels and works its way through
different sinuses.
A large saclike space in the body is
called a sinus.
 Ammonia is removed from the blood
and released out of the body by tube-
shaped called nephridia.
Mollusks were among the first inhabitants of the
Earth. Fossils of mollusks have been found in
rocks and date back over 500 million years.
Mollusk fossils are usually well preserved

because of their hard shell.

Most mollusks have a soft, skin-like organ

covered with a hard outside shell.


Some mollusks live on land, such as the snail

and slug.


Some mollusks live on land, such as the snail

and slug.
Other mollusks live in water, such as the oyster,

mussel, clam, squid and octopus.
Land living mollusks, like the snail, move slowly on a
flat sole called a foot.
Ocean living mollusks move or swim by jet
propulsion. They propel themselves by ejecting water
from their body.
For example, the squid ejects water from a cavity

within its body, and the scallop ejects
water to move by clamping its shell
closed.
Other ocean living mollusks, like the oyster, attach
themselves to rocks or other surfaces, and can't
move.
Other ocean living mollusks, like the oyster, attach
themselves to rocks or other surfaces, and can't
move.
They feed by filtering small food particles from

water that flows through them.
Despite their name, the cuttlefish is not a fish, but a
mollusk.
mollusk.
The cuttlefish is native to all of the oceans of the

world, but are more common in shallow coastal
temperate and tropical waters.
mollusk.

The cuttlefish has an internal shell or bone, called the

cuttlebone, that helps them to be buoyant.
mollusk.


Attached to this body structure is the head with eight

arms and two feeding tentacles.
mollusk.


Attached to this body structure is the head with eight

arms and two feeding tentacles.
The cuttlefish can easily camouflage itself by changing

its skin color and pattern to blend in with its
background.
This helps the cuttlefish to hide from predators, and
the sneak up on its prey.
Like the squid and octopus, the cuttlefish can eject ink
in an effort to escape from predators.
Like the squid and octopus, the cuttlefish can eject ink
in an effort to escape from predators.
This ink, called sepia, was once used as a die to create

ink used by artists.
Activity # 6.2
Observe your locality and notice the other species in

aquaculture aside from the fish.
Take a close look also of the different opportunities

available and how lucrative an aquaculture venture can
become when one take full advantage of opportunities
around mollusks.
Document your activity by taking pictures of these findings

in your cellphone or camera.

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mollusks

Welcome to Module 6 dear AGRIB109_A students! This sixth and last

It is my continued hope that you ceaselessly have fun and sustained

1. Identify the other aquatic species in

Biofilters-strain the water

Gastropoda Gastropods Shell-less Aplacophora,

Cephalopoda cephalopod Only small internal Octopi, squids,

◦ Visceral mass contained within the shell; it generally holds the

Mollusk foot are flat structures for crawling,

Mollusk shell is made by glands in the

A siphon is a tubelike structure through which water

Land snails and slugs typically live only in moist

They respire using a mantle cavity that has a large

 Blood is pumped through vessels by a

Mollusk fossils are usually well preserved

Mollusk fossils are usually well preserved

Most mollusks have a soft, skin-like organ

Mollusk fossils are usually well preserved

Most mollusks have a soft, skin-like organ

Some mollusks live on land, such as the snail

Mollusk fossils are usually well preserved

Most mollusks have a soft, skin-like organ

Some mollusks live on land, such as the snail

Other mollusks live in water, such as the oyster,

For example, the squid ejects water from a cavity

They feed by filtering small food particles from

The cuttlefish is native to all of the oceans of the

The cuttlefish is native to all of the oceans of the

The cuttlefish has an internal shell or bone, called the

The cuttlefish is native to all of the oceans of the

The cuttlefish has an internal shell or bone, called the

Attached to this body structure is the head with eight

The cuttlefish is native to all of the oceans of the

The cuttlefish has an internal shell or bone, called the

Attached to this body structure is the head with eight

The cuttlefish can easily camouflage itself by changing

This ink, called sepia, was once used as a die to create

Observe your locality and notice the other species in

Take a close look also of the different opportunities

Document your activity by taking pictures of these findings

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