What is the function of the foot in mollusks?
In muscle: Mollusks …highly muscular organ called the foot, through which muscle fibres run in all directions. The foot of a gastropod is a flat structure used for crawling.
What is a mollusk?
A mollusk generally refers to a member of the large group of soft-bodied invertebrates within the phylum Mollusca. Examples of mollusks include snails, clams, oysters, squids, and mussels. This group of organisms varies greatly in habitats and appearance, but they have a few universal features that will be elaborated on later in this lesson.
What are Mollusca shells used for?
Mollusca. Molluscs have, for centuries, also been the source of important luxury goods, notably pearls, mother of pearl, Tyrian purple dye, and sea silk. Their shells have also been used as money in some preindustrial societies.
What is the function of the foot of a gastropod?
The foot of a gastropod is a flat structure used for crawling. Waves of muscular contraction travel along its length, moving the animal slowly over the ground. The foot of a bivalve mollusk is a bulbous…
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What is the function of the foot in a mussel?
The soft tissues include a large muscular foot used for locomotion, an enveloping mantle that secretes the shell, anterior and posterior adductor muscles that enable to the animal to close its shells, labial palps that move food particles to the mouth, and two pairs of gills.
What mollusks use their feet to crawl?
GastropodsGastropods include snails and slugs. They use their foot to crawl. They have a well-developed head. There are many thousands of species of sea snails and sea slugs, as well as freshwater snails, freshwater limpets, land snails and land slugs.
What does the foot of Mollusca consist of?
In most gastropods the foot is an elongated, flat creeping sole that contains numerous mucus-producing gland cells. In the members of the subclass pulmonata the foot is undivided with a very large flat lobe containing a large pedal gland. In these cases the foot is used for creeping on a mucous trail.
What is the function of the feet in molluscs How are the feet of molluscs related to the name given to the classes of this phylum?
1 Answer. The mollusc foot has the function of locomotion, support, fixation, digging in the environment and sometimes of holding prey. The terminations of the names given to the main mollusc classes come from the Greek word “podos” that means foot.
What does a snail use its foot for?
It lacks legs but moves thanks to a “muscular ventral foot.” The foot has a wave-shaped movement produced by muscular contractions that make the snail “glide” while the foot secretes a slippery mucus that reduces the friction on the surface in which it moves.
How does a clam use its foot for movement?
With the foot wedged into place, retractor muscles then pull the shell downward. The adductor muscles holding the shell closed then relax, allowing the shell to open and to remain anchored in the sediment. This burrowing cycle is then repeated.
Do all mollusks have a foot?
Most mollusks move with a muscular structure called a foot. The feet of different kinds of mollusks are adapted for different uses, like crawling, digging, or catching prey. Many mollusks have an organ called a radula (RAD you lah), which is a flexible ribbon of tiny teeth.
What is a clam foot?
The clam's foot is used to dig down into the sand, and a pair of long incurrent and excurrent siphons that extrude from the clam's mantle out the side of the shell reach up to the water above (only the exit points for the siphons are shown). Clams are filter feeders.
What do bivalves use their foot for?
As filter feeders, bivalves gather food through their gills. Some bivalves have a pointed, retractable "foot" that protrudes from the shell and digs into the surrounding sediment, effectively enabling the creature to move or burrow.
How the foot is adapted for locomotion in a snail?
A snail uses its single long, muscular foot to crawl on a layer of mucus-like slime that it secretes. This mucus has unusual physical properties, and scientists assumed that these sticky properties were essential for snail movement.
What is muscular foot in snail?
The muscular foot of the snail comes outside and attaches to the ground during locomotion. The foot of a snail has a special gland that produces slimy mucus to make slippery track to help it move smoothly. Snails and slugs are collectively known as gastropods.
How does the foot of a bivalve differ from the foot of a cephalopod or the foot of a snail?
The foot of the bivalve is one singular mass. Its main purpose is for burrowing or digging. The cephalopod foot is made up of tentacle and sucker like structure that are used for locomotion as well as for hunting prey. The snail foot is also one singular mass but is used mainly for crawling like movements.
Why do molluscs have different foot shapes?
16.63). Variation of foot is primarily due to various physiological activities like creeping or crawling, burrowing, leaping, looping, swimming, reproduction, etc. Besides these, in parasitic and sedentary forms, the modification of foot occurs in the form of sucker, byssus apparatus, etc.
How does the foot help the substratum?
The foot helps to creep or glide on the rocky substratum by the waves of muscular activity which is lubricated by mucus glands. It also helps to be attached firmly to the rocks by generating a suction, secreting the mucus along the girdle.
How does the water expulsion of a nautilus work?
The expulsion of water is achieved by muscular contraction of the siphon or funnel. In Nautilus (Subclass Nautiloidea) the funnel consists of two separate lateral muscular lobes that fold together to form a tube-like structure which serves for jet propulsion. The funnel of Nautilus is not a complete tube.
What is the foot in Vema?
In Neopilina and Vema the foot is centrally placed, broad, flattened and almost circular in outline. The foot helps in creeping by muscular movement.
How does the foot extend forward?
Foot is extended forward into the mud or sand by the extension of the protractor muscles, and the retractor muscles help to draw the animal deeper into the substrate. The retractor muscles contract sequentially, so the shells rock forward and backward and the animal progresses through the sediment.
What is the foot of Chiton?
Class Polyplacophora: In Polyplacophora, the foot of Chiton is broad, muscular and flattened that extends the entire ventral surface of the body (Fig. 16.65A). In Chitonellus and Crypsoplax the foot is narrow.
What is the simplest form of foot?
The primitive and simplest form of foot in Mollusca is considered to be a broad ventral flat sole having the above mentioned three regions (e.g., Polyplacophora, Gastropoda, Bivalvia [Protobranchia]).
What is the headfoot of a mollusc?
The head-foot is the more active area, containing the feeding, cephalic sensory, and locomotor organs. It depends primarily on muscular action for its function.
Where does the calcium in a marine mollusk come from?
There is great variation in shell structure. Calcium for the shell comes from environmental water or soil or from food. The first shell appears during the larval period and grows continuously throughout life.
What is the mantle cavity?
The mantle cavity houses gills (ctenidia) or a lung, and in some molluscs the mantle secretes a protective shell over the visceral mass. Modifications of the structures that make up the head-foot and the visceral mass produce the great diversity of patterns observed in Mollusca.
How many teeth does the radula have?
There may be a few or as many as 250,000 teeth, which, when protruded, can scrape, pierce, tear, or cut.
Where do molluscs withdraw their head?
Many molluscs can withdraw their head or foot into the mantle cavity, which is surrounded by the shell, for protection. In primitive form, a mollusc ctenidium (gill) consists of a long, flattened axis extending from the wall of the mantle cavity (Figure 16-4).
What is the role of the mantle cavity in molluscs?
The mantle cavity (Figure 16-2) plays an enormous role in the life of a mollusc. It usually houses respiratory organs (gills or lung), which develop from the mantle , and the mantle’s own exposed surface serves also for gaseous exchange.
What is secreted mucus used for?
Secreted mucus is often used as an aid to adhesion or as a slime tract by small molluscs that glide on cilia.
What are the most important things that molluscs have done for centuries?
Molluscs have, for centuries, also been the source of important luxury goods, notably pearls, mother of pearl, Tyrian purple dye, and sea silk. Their shells have also been used as money in some preindustrial societies. Mollusc species can also represent hazards or pests for human activities.
Where did the word "mollusk" come from?
The words mollusc and mollusk are both derived from the French mollusque, which originated from the Latin molluscus, from mollis, soft. Molluscus was itself an adaptation of Aristotle 's τὰ μαλάκια ta malákia (the soft ones; < μαλακός malakós "soft"), which he applied inter alia to cuttlefish. The scientific study of molluscs is accordingly called malacology.
How do filter feeders work?
Filter feeders are molluscs that feed by straining suspended matter and food particles from water, typically by passing the water over their gills.
How many species of molluscs are there?
Estimates of accepted described living species of molluscs vary from 50,000 to a maximum of 120,000 species. The total number of described species is difficult to estimate because of unresolved synonymy.
What is the shell of a mollusc made of?
This has a single, " limpet -like" shell on top, which is made of proteins and chitin reinforced with calcium carbonate, and is secreted by a mantle covering the whole upper surface. The underside of the animal consists of a single muscular "foot". Although molluscs are coelomates, the coelom tends to be small.
How many classes of mollusks are there in the phylum?
The phylum is typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates —and either the giant squid or the colossal squid is the largest known invertebrate species.
What is the largest phylum of marine organisms?
Many taxa remain poorly studied. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat.
Which layer of the shell prevents other organisms from growing on or boring into the shell?
proteinaceous layer called the periostracum. Prevents other organisms such as barnacles and hydroids from growing on or boring into the shell
What is the function of cepbalopods?
cepbalopods- pumped by a simple heart past the gills and then supplies body organs with oxygen and removes waste.
Overview
Hypothetical ancestral mollusc
Because of the great range of anatomical diversity among molluscs, many textbooks start the subject of molluscan anatomy by describing what is called an archi-mollusc, hypothetical generalized mollusc, or hypothetical ancestral mollusc (HAM) to illustrate the most common features found within the phylum. The depiction is visually rather similar to modern monoplacophorans.
Etymology
The words mollusc and mollusk are both derived from the French mollusque, which originated from the Latin molluscus, from mollis, soft. Molluscus was itself an adaptation of Aristotle's τὰ μαλάκια ta malákia (the soft ones; < μαλακός malakós "soft"), which he applied inter alia to cuttlefish. The scientific study of molluscs is accordingly called malacology.
The name Molluscoida was formerly used to denote a division of the animal kingdom containin…
Definition
The most universal features of the body structure of molluscs are a mantle with a significant cavity used for breathing and excretion, and the organization of the nervous system. Many have a calcareous shell.
Molluscs have developed such a varied range of body structures, finding synapomorphies (defining characteristics) to apply to all modern groups is difficult. The most general characteristic of mol…
Diversity
Estimates of accepted described living species of molluscs vary from 50,000 to a maximum of 120,000 species. The total number of described species is difficult to estimate because of unresolved synonymy. In 1969 David Nicol estimated the probable total number of living mollusc species at 107,000 of which were about 12,000 fresh-water gastropods and 35,000 terrestrial. The Biv…
Ecology
Most molluscs are herbivorous, grazing on algae or filter feeders. For those grazing, two feeding strategies are predominant. Some feed on microscopic, filamentous algae, often using their radula as a 'rake' to comb up filaments from the sea floor. Others feed on macroscopic 'plants' such as kelp, rasping the plant surface with its radula. To employ this strategy, the plant has to be large enough for the mollusc to 'sit' on, so smaller macroscopic plants are not as often eaten as …
Classification
Opinions vary about the number of classes of molluscs; for example, the table below shows seven living classes, and two extinct ones. Although they are unlikely to form a clade, some older works combine the Caudofoveata and Solenogasters into one class, the Aplacophora. Two of the commonly recognized "classes" are known only from fossils.
Classification into higher taxa for these groups has been and remains problematic. A phylogenet…
Evolution
Good evidence exists for the appearance of gastropods (e.g., Aldanella), cephalopods (e.g., Plectronoceras, ?Nectocaris) and bivalves (Pojetaia, Fordilla) towards the middle of the Cambrian period, c. 500 million years ago, though arguably each of these may belong only to the stem lineage of their respective classes. However, the evolutionary history both of the emergence of molluscs …