Bivalve Mollusk – Anatomy, Life Cycle And 6 Important Classes

Bivalve Mollusk

Last updated on September 3rd, 2022 at 03:16 pm

Mimicking fish, bivalve mollusk breathes through their gills. Since they gather foods through their gills, this makes them a filter feeder. Some bivalves have a pointed, retractable “foot” that extends from the shell and goes into the surrounding sediment, efficiently making it possible for the animal to burrow or move.

Some types of bivalve mollusk, like clams, mussels, scallops, and oysters, have an external covering that is a two-part hinged shell that contains a soft-bodied invertebrate.

Bivalve mollusk even makes their own shells. An internal organ called the mantle produces calcium carbonate so that as the inner invertebrate grows, the external shell offers a roomier house.

Lots of bivalve mollusk types play crucial functions in marine and water environments by serving as habitat, filtering the water, and serving as prey for a range of sea life.

This species of a diverse group, approximated at about 9,200, populates practically the whole world ocean, from the balmy tropics to the sub-zero Arctic, and from the deep ocean to rocky and sandy coastlines. A couple of them have actually even settled around hydrothermal vents discovered deep in the Pacific Ocean, which is below 13,000 feet.

Bivalve mollusk definition

Bivalve Mollusk

Bivalve mollusk is animals that live inside water and have 2 valves that safeguard the soft body parts. The valves are produced by the mantle, a soft tissue that leaves a scar (the pallial line) where it is linked to the inside of the shell. The muscles that hold the 2 valves together likewise leave scars on the inside of the shell, as do the siphons, through which food goes in and out of the body.

The length and shape of the siphon scar is useful for translating the burrowing routines of a bivalve mollusk. Different scars are also features of different bivalve types.

Unlike the valves of brachiopods, clam valves are generally of comparable shapes and sizes. The 2 shells are hinged together by a strong ligament. Little teeth and sockets might likewise exist in the hinge location, which includes strength to the hinge and avoid the 2 valves from slipping apart.

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Origin of the Bivalves (with Bivalve mollusk)

Bivalve mollusk comes from the Cambrian period, however, it did not end up being plentiful till the Ordovician duration. They are not especially typical in the Paleozoic rock of Wisconsin, however, they in some cases can be discovered within big groupings of other Ordovician fossils.

The phylum of the animal kingdom, consisting of the classes Gastropoda, Bivalvia, Cephalopoda, Scaphopoda, Monoplacophora, Polyplacophora, Caudofoveata, and Solenogastres. These animals have an unsegmented bilateral body, with the majority of the parts and organs combined, but not serially repeated.

Bivalve mollusk are specified by a tissue called the mantle, which forms the shell and secures most organs. A lot of mollusks like clams, slugs, snails, nudibranchs, octopuses, squid, chitons, tusk shells, and numerous others are all typically called mollusks, have a calcareous shell, which can be univalve, bivalve, or multivalve.

A member of the phylum Mollusca; which can also be spelled as mollusk (most particularly in the UK) … Some, however, not all, of these also by the more typical name “seashells.”

Many mollusks bear a shell of several parts made from calcium carbonate. There are roughly 120,000 types of living mollusks, and a lot more extinct types recorded as fossils back to the Cambrian Duration over 500 million years ago.

Mollusks are the 2nd biggest phylum in the world, just a little lower than the insects, and are the biggest taxonomic group in the sea.

Researchers presently acknowledge 8 classes of mollusks

What are the 6 mollusks?

  1. Gastropoda (slugs and snails)
  2. Monoplacophora (the primitive limpets)
  3. Bivalvia
  4. Polyplacophora (chitons)
  5. Cephalopoda (squids and octopuses)
  6. Scaphopoda (tusk shells)

And 2 classes of worm-like mollusks which are

  1. Caudofoveata
  2. Solenogastres usually called “aplacophoras.”.

Bivalve mollusk anatomy

Bivalve Mollusk

Bivalves differ considerably in overall shape. Some, such as the cockles, have shells that are almost globular; cockles can leap by flexing and straightening their foot.

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Others, such as the razor clams, are burrowing experts with extended shells and an effective foot adapted for fast digging. The shipworms, in the household Teredinidae, have actually significantly lengthened bodies, however, their shell valves are much reduced and limited to the anterior end of the body, where they operate as scraping organs that allow the animal to dig tunnels through the wood.

The nervous system of bivalve mollusk

The inactive routines of the bivalves have actually indicated that in general, the nervous system is less complicated than in many other mollusks.

The animals have no brain; the nerve system includes a nerve network and a series of paired ganglia. In all, however the most primitive bivalves, 2 cerebropleural ganglia are on either side of the esophagus. The cerebral ganglia manage the sensory organs, while the pleural ganglia supply nerves to the mantle cavity.

The pedal ganglia, which manage the foot, are at its base, and the visceral ganglia, which can be rather big in swimming bivalves, are under the posterior adductor muscle.

These ganglia are both linked to the cerebropleural ganglia by nerve fibers. Bivalves with long siphons might likewise have siphonal ganglia to manage them.

Diet plan

As known that bivalves are filter feeders, i.e. they can strain little food particles from water. Water goes in through the inhalant siphon, goes through the gill, which takes in oxygen from the water and exits through the exhalent siphonal popularly called the out current siphon.

The gill traps food particles and carries them to the mouth.

Bivalves reside in a range of environments: Some live on top of seafloor sediment, others live in seafloor sediment, using their muscular foot to burrow within the bottom sediments.

The shape of the shell can be connected to the environment in which the animal lives.

Reproduction and life cycles

Bivalve Mollusk

Many bivalve types are separated into either male or female members and some types are able to produce both sperm and eggs, sexual dimorphism is unusual.

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In the types that are separated into either male or female, there is generally an equivalent department of the sexes. Synchronized hermaphroditism takes place when egg-producing roots and sperm-producing tubules intermingle in the gonads, or the gonads might be turned into a different ovary and testis, as in all agents of the subclass Anomalodesmata.

Bivalve sperm have 2 flagella. A lot of eggs are little, and integrated spawning lead to the discharge of both kinds of gametes into the sea for external fertilization.

Hermaphrodites generally get sperm from another individual through the incurrent siphon. The embryos are then brooded, and brooding normally happens within the ctenidia. There the fertilized eggs, well endowed with yolk, develop straight away (i.e without a larval phase), and the young are launched as mini-adults.