Molluscs: Characteristics, Structure, Organ System, Reproduction, Classification, Role
Mollusca comes from the Latin, namely "molluscus" which means soft. Mollusca is a type of soft animal that either has a graft (coat) or does not have a graft. Such as various types of shellfish, chitons, snails, squid, and their relatives.
Molluscs are the second largest phylum in the animal kingdom after the phylum Arthropoda. The number of mollusks is currently estimated at 75 thousand species, and an additional 35 thousand species in the form of fossils. Mollusks have a heterotrophic way of life, namely by eating algae, shrimp, fish, or the remains of organisms. Habitat is in fresh water, sea, and on land.
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Table of contents
Following are the characteristics of Mollusks:
- Sizes and bodies vary
- It is a tripoblastic coelomate
- Is a hermaphrodite animal, which has 2 sexes (male and female) in one body
- Is an invertebrate animal (does not have a backbone)
- Soft body shape and not segmented
- Live in water and on land
- Has a ring of conditions which is a nervous system
- Has a radula (toothed tongue)
- The excretory organs are nephridia
- Have a bilaterally symmetrical body structure
- Reproduce sexually
- Heterotrophic animal
- The body consists of legs, visceral mass, and minerals
Mollusc Body Structure
The mollusk body consists of three parts as follows:
- Feet: Function for moving, crawling, or digging. Some types of mollusk legs are replaced with tentacles that function in catching prey.
- Visceral Mass: Contains digestive, excretory, and reproductive organs. The visceral mass is protected by the mantle.
- Coat: Thick tissue that serves to protect the visceral mass. The mantle has a fluid cavity that contains the gill holes, anus, and excretory fluid. The coat also functions as an excretory tool in the components that make up the shell (body armor).
Mollusc Organ System
1. Bloodstream system
The circulatory system in mollusks is open, except for the class cephalopod. Open circulatory system i.e. blood flows through open cavities in the body and there are no arteries or veins which can increase blood pressure, so that blood pressure will slow down and make organs flooded by blood. The circulatory system consists of the heart and blood vessels, the heart consists of one or two atria and one ventricle.
2. Digestive system
The digestive system consists of the mouth, esophagus, stomach, intestines, and anus. In certain types, there are organs such as the jaw and a serrated tongue in the mouth that can move forward and backward.
3. Nervous system
The nervous system consists of a nerve ring that surrounds the esophagus and other nerve fibers spreading from the ring to various organs.
4. Excretion System
The excretory system is in the form of nephridia which acts similar to the kidney, nephridia is able to excrete metabolic waste in the form of liquid.
5. Respiration system
The respiratory system of Molluscs is different. Animals that live in water rely on gills, while animals that live on land rely on lungs. However, it can also occur through the exchange of air contained in the mantle, this system functions much like the lungs.
Mollusks are hermaphrodites, which have male and female genitals in one individual (one housed), but some also have separate genitals (two housed). Therefore, the way of reproduction using internal fertilization.
Mollusks are classified according to body structure. Its body structure is divided into five, namely:
Amphineura is a type of mollusk that is still primitive and lives around the coast. Amphineura has a bilaterally symmetrical body and has several gills in the mantle cavity. An example of an amphineura is a chiton.
Gastropods are animals that rely on their stomachs as legs and have habitats on land, fresh water, and in the sea. Generally, Gastropods have a body layer (shell). An example of a gastropod is a snail.
Cephalopods use their heads as a means of locomotion. Cephalopods have an endoskeleton, an exoskeleton, or neither. The body is bilaterally symmetrical and consists of a head, neck, and body. An example of a cephalopod is the squid.
Scaphopods have a sharp shell, shape like a trumpet, have small feet, on the head there are several tentacles, and have no gills. Schaphopoda can be found in the sea or on the beach. An example of a scaphopod is dentalium vulgare.
5. Pelecypoda (Bilvalvia)
Pelecypoda has legs with an ax-like shape located anteriorly. Bilvalves are shelled animals that consist of two parts and have a well-developed nervous system and brain. Pelecypoda habitat in fresh water and sea. Examples of pelecypoda are meleagrina (pearl shells), anadonta (mussels), ostrea (oysters), panope generosa (giant clams).
Role of Mollusca
Mollusks have an important role for human life, many types of mollusks are used in various ways. Here are the various uses:
- As jewelry (shells and oysters)
- As food ingredients (squid, cuttlefish, clams)
- Sea clam shell powder is useful as an ulcer medicine
- And so forth
Thus the discussion about molluscs and their characteristics, structure, organ systems, reproduction, classification, and their role for humans. In addition, for those of you who want to find out about epithelial tissue,Tamilchill also serves it.