Characteristics of Mollusks

Mollusks are animals that are widely abundant on the planet, mollusks are animals that occupy a key place in the food chain and are only surpassed in abundance by insects.

They are called mollusks from Latin where there is the word "mollusca" which at the same time derives from another Latin word "Molluscum" and its meaning translates directly into "soft".

One of the main characteristics of mollusks is that they are invertebrates.

Main characteristics of mollusks:

origins.- The origins of the mollusks are really uncertain but

think that these are some of the first living entities that have existed on the planet.

Varieties.- The varieties of mollusks can be calculated in more than one hundred thousand species, currently existing and some experts argue that there were 25 to 40 thousand species already extinct. Among the existing ones there are mollusks that have a shell and other mollusks that do not have a shell.

Classification.- Mollusks have been classified into eight different ones, which are:

1. Caudofoveata.- This classification has an approximate of 70 species.

These mollusks are animals that do not have eyes, feet and tentacles, their habitat is in small tunnels that dig in the bottom of the sea. They feed on some sedimentivorous animals, such as faraminifera and diatoms, among which we can understand earthworms and mealybugs.

They can be separated or differentiated as:

• Chaetodermatiae
• Limifossoridae and
• Prochaetodermatidae

2. Solenoid.- This variant consisting of approximately 250 species.

These are very small animals that are between 2.5 and 6 cm in length, they also lack tentacles, eyes and a shell, but they do have feet. These are distinguished by being hermaphrodites and its fertilization is mutual, the subdivisions that are known are:

• Cavibelonia
• Neomeniamorpha
• Pholidoskepia and
• Sterrofustia

Their diet is also based on debris and protozoa from the substrate, as with other mollusks.

3. Monoplacophora.- These consist of more than 20 species; These were classified as extinct, but recently around 20 species or variants have been found.

Its body is segmented symmetrically, similar to some insects such as dragonflies, or shells; these are cataloged as "Metamer " or "Metamers".

4. Polyplacophora.- In this, more than 650 species are calculated, they are flattened mollusks and are called chitons, and are subdivided into:

• Chitonida and
• Neoloricata

It is called polyplacophora, because its exoskeleton is made up of multiple plates.

Feeding.- Their diet is based on algae and there is no news that they consume other living beings.
Reproduction.- Its reproduction is sexual, and in general terms the female releases the eggs when she perceives the sperm of the male previously thrown. Even so, there are internal reproductions or direct fertilization in some varieties of polyplacophora.
Habitat.- Their place of life is in relatively shallow rocky areas, but it is known that there are some varieties that are capable of surviving in deep waters.

5. Gastropoda.- Snails and similar animals are concentrated here.

• Slugs
• Snails etc.

Reproduction.- Its reproduction is generally hermaphrodite, although it is believed that there may be some variety that has separate sexual reproduction.
Feeding.- The diet is generally herbivorous, and in the marine subspecies there may be some that feed on small marine animals.
Habitat.- Its habitat is very stranded, as there are varieties of Polyplacophora, terrestrial and marine varieties.

6. Scaphopoda.- Only a few species have been detected, these are conical shaped mollusks that are subdivided into two:

• Dentalida and
• Godilida.

Feeding.- Their diet is of small organisms found in the sand, such as bivalos, kinorhincos and foraminifera.
Habitat.- They are generally buried in the marine sand, either shallow or on the beaches.
Reproduction.- The reproduction of the Scaphopoda is of separate gametes, their fertilization is externally and larvae are produced and produced, either trochophore or veligera.

7. Bivalvia.- The number of species exceeds 14 thousand, it consists of organisms with two plates, such as clams.

Reproduction.- Their reproduction is generally sexual, although there are some species with hermaphroditic reproduction.
Feeding.- The feeding of the Bivalvia is through the absorption of water, where they absorb microscopic organisms.
Culture.- Some varieties of these animals are used as food for humans and a cultivation and treatment industry has developed.

8. Cephalopoda.- Of this, more than 810 species have been found and octopuses and squids are well known.

Feeding.- These animals feed on small fish, other mollusks and some crustaceans such as shrimp.
Reproduction.- The reproduction of the cephalopods is by means of eggs that are fertilized by the male; the female holds the fertile eggs on a wall or ceiling of underwater caves and for this they use a sticky membrane or bag that supports the hatching time.

General features

Habitatgeneral.- The mollusk in general terms is capable of surviving at almost any height of sea level and in almost any climate, including some deserts.

Its environment is basically aquatic, but there are mollusks such as slugs and snails that, due to their movements (especially at night), can travel long distances.

Evolutionary plasticity.- The plastic nature of these animals allows them to adapt to the environment in which they survive and their structure has helped him develop and partially control the defects that his structure gives him establishes.

Your digestion.- Mollusks have a perfectly developed digestive system, it begins with the mouth and basin with a radula with a cartilaginous section that has small small teeth or similar structure the mouth, it has a stomach that metabolizes and destroys leaves, algae, and even small insects or fish, as happens with octopuses and some squid.

Her shell.- This is not found in all mollusks, as it is a defensive quality that is believed to have been around for a short time. similar in many of the mollusks, especially in terrestrial ones such as snails, and in some marine mollusks such as oysters. Its function is defensive and the shell has separated into some small varieties:

• Gastropods.- They have a one-piece shell like snails.
• Bivalves.- They have a two-piece shell like in sea oysters.
• Cephalopods.- This is how mollusks that do not have a shell are called, such as octopuses and squid.

Your nervous system.- This aspect of mollusks can vary from entity to entity, as it can have two cords that move to the back ending in the mass of visors, and the other to the so-called foot.

Foot.- It is how the organ that characterizes mollusks is called, it is the impeller with which slugs and snails move.

Reproductive system.- This can be simple sexual or hermaphroditic, the snails can fertilize both in unison, more visible effect in slugs.

After fertilization, these produce eggs that are abandoned in one place and are subsequently produced, these hatch and mollusks that have similar qualities to their predecessors.

Food source.- Because it is one of the most abundant living entities on the planet, it is also an entity with a primordial position in the food chain, which is why it occupies a preferential place in our chain food.