Types of molluscs: characteristics and examples

Author: Laura McKinney
Date Of Creation: 4 August 2021
Update Date: 16 December 2024
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Mollusca | Gastropods-Bivalves-Cephlapods |
Video: Mollusca | Gastropods-Bivalves-Cephlapods |

Content

You molluscs they are a large group of invertebrate animals, almost as numerous as arthropods. Although they are very diverse animals, it is possible to find certain characteristics that classify them differently. Do you want to know more about them?

In this article by PeritoAnimal, let's know the types of existing molluscs, their characteristics and classification, and we will also have a list of molluscs for you to know a little of the diversity. Keep reading!

what are molluscs

the molluscs are invertebrates whose integument is soft like that of the annelids, but its adult body is not segmented, although some may be protected by a shell. It is the most numerous group of invertebrate animals after arthropods. There are about 100,000 species, of which 60,000 are gastropods. In addition, 30,000 fossil species are also known.


Most of these animals are molluscs. marinebenthic, that is, they live at the bottom of the sea. Many others are terrestrial, like some snails. The great diversity that exists means that these animals have colonized a large number of different habitats and therefore all diets are present within the different types of molluscs.

Also find out in PeritoAnimal which types of corals, marine and terrestrial.

Molluscs: characteristics

Molluscs are a very diverse group, and finding characteristics common to all of them is a daunting task. Therefore, we will present the most common features, although there are many exceptions:


The shellfish body is divided into four main regions:

  • cloak: it is the dorsal surface of the body that can secrete protection. This protection has a chitinous and protein origin that later creates limestone deposits, spikes or the shell. Some animals that don't have shells have chemical defenses.
  • locomotive foot: is ciliated, muscular and with mucous glands. From there, several pairs of dorsoventral muscles emerge that serve to retract the foot and fix it to the mantle.
  • cephalic region: in this region we find the brain, mouth and other sensory organs.
  • paleal cavity: here are located the osphradia (olfactory organs), body orifices (anus) and the gills, called ctenids.

O shellfish digestive apparatus has some characteristic features:


  • Stomach: these animals have extracellular digestion. Digestible particles are selected by the digestive gland (hepatopancreas), and the rest passes into the intestine to produce stool.
  • radula: this organ, located inside the mouth, is a membrane in the form of a toothed tape, supported by the odontophore (mass of cartilaginous consistency) and moved by complex musculature. Its appearance and movement are similar to a tongue. The chitinous teeth that the radula has tear the food. Teeth that age and wear out fall out, and new ones form in the root sac. Many solenogastros do not have the radula, and no bivalve does.

However, in addition, your circulatory system is open, only the heart and the nearest organs have vessels. The heart is divided into two atria and a ventricle. These animals do not have an excretory device determined. They have metanephrids that collaborate with the heart, which is an ultrafilter, producing primary urine that is reabsorbed in the nephrids, which are also responsible for regulating the amount of water. O reproductive system has two gonads in front of the pericardium. Gametes are evacuated to the paleal cavity, usually linked to nephrids. Molluscs can be dioecious or hermaphrodite.

classification of molluscs

The mollusc phylum divides into eight classes, and all have living species. The classification of molluscs are:

  • Caudofoveata Class: are molluscs in worm shape. They do not have shells, but their bodies are covered with calcareous and aragonitic spikes. They live buried in the ground upside down.
  • Solenogasters Class: they are animals very similar to the previous class, so much so that historically they have been included in the same group. They are also worm-shaped, but instead of living buried, they live free in the ocean, feeding on cnidarians. These animals also have calcareous and aragonitic spikes.
  • Monoplacophore Class: are very primitive molluscs. your body is covered by a single shell, like half a clam, but they have a muscular foot like snails.
  • Polyplacophora class: At first glance, they are similar to some type of crustacean, like the armadillos-de-garden. The body of these molluscs is covered by a set of plates reinforced with magnetite. They also feature a muscular crawler foot and a radula.
  • Scaphopoda class: these molluscs have a very long body, as well as their shell, which is shaped like a horn, and that is why they are known as fang shells. It is one of the best known types of marine molluscs.
  • Bivalvia class: bivalves, as the name implies, are molluscs whose body is between two valves or shells. These two valves close thanks to the action of some muscles and ligaments. The best known types of bivalve molluscs are clams, mussels and oysters.
  • Gastropoda Class: gastropods are known snailsand slugs, both terrestrial and marine. They have a well-differentiated cephalic area, a muscular foot for crawling or swimming, and a dorsal shell. This shell may be absent in some species.
  • Cephalopoda Class: the cephalopod group is composed of octopus, sepia, squid and nautilus. Despite what it may seem, they all feature shells. The most obvious is the nautilus, since it is external. Sepia and squid have a more or less large shell inside. The shell of the octopus is almost vestigial, only two thin limestone strands remain inside its body. Another important characteristic of cephalopods is that, in this class, the muscular foot present in molluscs has been transformed into tentacles. May have between 8 and more than 90 tentacles, depending on the species of mollusc.

Shellfish example

Now you know the characteristics and classification of molluscs. Below, we'll explain about some types of shellfish and examples:

1. Chaetoderma elegans

shaped like worm and shellless, this is one of the types of molluscs that belongs to the class Caudofoveata. It has a tropical distribution in the Pacific Ocean. can be found at depths of 50 meters to more than 1800 meters.

2. Neomenian carinata

And another vermiform mollusc, but this time it belongs to the Solenogastrea family. These types of molluscs are found in a depth range between 10 and 565 meters, living freely in the Atlantic Ocean, on the coasts of Portugal.

3. Sea cockroach (Chiton articulatus)

The sea cockroach is a kind of molluscpolyplacophora endemic to Mexico. It lives in the rocky substrate of the intertidal zone. It is a large species, reaching 7.5 centimeters in length among the types of molluscs.

4. Antalis vulgaris

It is a species of scaphopod mollusk with tubular or prey-shaped shell. Its color is white. Live in sandy and muddy substrates shallow, in intertidal zones. These types of molluscs can be found along the Atlantic and Mediterranean coasts.

5. Coquina (Donax trunculus)

Coquinas are another type of shellfish. They are bivalves small in size, which usually live on the Atlantic and Mediterranean coasts. They are very popular in Mediterranean cuisine. They can live in the subtidal area about 20 meters deep.

6. European Flat Oyster (Ostrea edulis)

Oysters are one of the types of molluscsbivalves of the Ostreoid order. This species can measure up to 11 centimeters and produces mother of pearl pearls. They are distributed from Norway to Morocco and the Mediterranean. Furthermore, they are cultivated in aquaculture.

See some examples of vertebrate and invertebrate animals in this PeritoAnimal article.

7. Caracoleta (Helix aspersa)

the snail is a kind ofgastropod mollusk with lung breathing, that is, it has no gills and lives on the earth's surface. They need a lot of moisture, and when they don't, they hide inside their shell for long periods of time to prevent drying out.

8. Common Octopus (Octopus vulgaris)

The common octopus is a cephalopod that lives in the Atlantic Ocean and the Mediterranean Sea. It measures about a meter in length and can change color thanks to its chromatophores. It has a high value for gastronomy.

Other types of molluscs

Do you want to know more? Next, we'll mention other species of molluscs:

  • Scutopus robustus;
  • Scutopus ventrolineatus;
  • Laevipilina cachuchensis;
  • Laevipilina rolani;
  • Tonicella lineata;
  • Diffuse Chiton or Phantom Chiton(Granular acanthopleura);
  • Ditrupa arietin;
  • River Mussel (margaritifera margaritifera);
  • Pearl mussel (private crystal);
  • Iberus gualtieranus alonensis;
  • Iberus gualtieranus gualtieranus;
  • African Giant Snail (Achatina sooty);
  • Sepia-common (Sepia officinalis);
  • Giant squid (Architeuthis dux);
  • Giant Pacific Octopus (Enteroctopus dofleini);
  • Nautilus belauensis.

Learn more about the animal world, check out our article on types of scorpions.

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