What is a mollusk with one shell or none?
Gastropods have one shell, or two, or none: beyond the canonical one-shelled snails, there are sacoglossans (Juliidae) that were originally described as bivalves [6], and while slugs and pelagic gastropods have reduced or lost the shell, several groups also possess secondary armour of subdermal calcareous spicules [7].
Which of the following is without shell?
Slug is a terrestrial gastropod mollusc without shell. Octopus is another example, which is an aquatic cephalopodan mollusc.
What is a shelled mollusk?
The mollusc (or mollusk) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.
Do molluscs have brains?
Molluscs, with the exception of the most highly developed cephalopods, have no brain in the strict sense of the word. Instead, the cell bodies (pericarya) of nerve cells are concentrated in nerve knots (ganglia) in important parts of the body. In gastropods, the ganglia originally have been dispersed over the body.
What are 4 examples of mollusks that do not have shells?
Mollusks without shells include squid, banana slugs, and octopi. Some mollusks are terrestrial, occurring in most environments on earth, while others live in the water for some or all of their life.
Why do molluscs have shell?
Mollusks often have a hard outer shell to protect their bodies. All mollusks have a thin layer of tissue called a mantle which covers their internal organs. The mantle produces the mollusk’s shell. Clams, oysters, snails, and octopuses are all mollusks.
Which class of mollusc has two shells?
Bivalvia
Bivalves—Clams and relatives (Class: Bivalvia) Bivalves have two shells (valves) held closed by powerful muscles. The shell is produced by the underlying mantle; it grows along the outer margins. They use their foot for burrowing.
What are some mollusks without a shell?
Epimenia babai is a species of solenogaster, mollusks without shells at any point in their development. Instead of a shell, this worm-like species is covered with hard sclerites that help protect it.
What kind of mollusc has a one part shell?
All other mollusc classes possess a real one-part shell and therefore are combined as Conchifera, shell-bearing molluscs. Among those there are the snails and slugs (Gastropoda), mussels and clams (Bivalvia), scaphopods (Scaphopoda) and squids, octopuses and cuttlefish (Cephalopoda).
Where does the word mollusk come from and what does it mean?
The word “mollusk” comes from the Latin “molluscus,” meaning soft. Though most people think of shelled animals when they picture mollusks, there are thousands of fascinating mollusks without shells that are just as eye-catching as any abalone or whelk.
What are the physical characteristics of a Mollusca?
The sexes are separate and the fertilization is external or internal. Development may be direct or indirect. Following are the classification of Mollusca: The body is cylindrical or bilaterally symmetrical. These are devoid of head, shell, mantel, nephridia, and foot. The digestive system is straight. Spicule-bearing cuticle covers the body.
What are some mollusks that have no shell?
Types of Mollusks – Characteristics And Examples Chaetoderma elegans. This species of glisten worm, is shaped a mollusk without a shell. Neomenia carinata. The Neomenia carinata is another vermiform mollusks without a shell, but belongs rather to the Solenogastres family. Sea cockroach (Chiton articulatus) The sea cockroach is a kind of endemic Polyplacophora marine mollusk from Mexico.
What are mollusk called if it has one shells?
Snails and conchs have single shells in the shape of a twisted cone. These mollusks are called univalves. Clams, oysters, scallops, and mussels have shells with two halves joined on one side. These mollusks are called bivalves.
What are the 3 classes of mollusks?
The three most commonly known classes of mollusca are: gastropoda, cephalopoda, and bivalvia. There are also lesser known classes: caudofoveata, solenogastres, polyplacophora, monoplacophora, and scaphopoda.
Do all molluscs have a shell?
Mollusks usually, but not always, have a shell , which is secreted by a body wall called the mantle. Many mollusks have a tongue of sorts, called a radula. The radula is rough like sandpaper. Mollusks have well developed body organs that are used in the respiratory, circulatory and nervous systems.
