Molluscs are either dioecious, with separate sexes, or hermaphroditic, one individual bearing both male and female sex organs. The eggs of aquatic species of bivalves and some species of gastropods develop into trochophores, which in turn usually develop into veliger larvae.

Are molluscs dioecious?

The animals in the phylum Mollusca (e.g., clams, snails, and squid) display a diversity of reproductive behaviour. The majority of the amphineurans (chitons) and pelecypods (e.g., clams, oysters) are dioecious—i.e., individuals are either male or female.

Are molluscs hermaphrodites?

The study reveals that about 40% of the 5600 mollusc genera are either simultaneous or sequential hermaphrodites. ... Sequential hermaphroditism, whatever its theoretical advantages over gonochorism, is not common among molluscs. Simultaneous hermaphroditism is common among the Euthyneura.

What type of reproduction do molluscs have?

Mollusks reproduce sexually, and most species have separate sexes. Sexual reproduction is achieved by the formation and fusion of gametes: sperm and eggs. Some species are hermaphrodites meaning that individuals are capable of forming both sperm and eggs.

Is Mollusca Oviparous or viviparous?

Birds, reptiles, amphibians, most fish, insects, mollusks, arachnids, and monotremes are oviparous animals. Most mammals are viviparous animals.

18 related questions found

Do all molluscs have shells?

You are probably familiar with a number of mollusks: they include the snails, octopuses, squids, clams, mussels, scallops, oysters, and chitons, among others. ... Though there are qualities that all mollusks share, you may be surprised to learn that not all of them have shells.

Are Mollusca normally oviparous?

Complete answer: Members of phylum Mollusca are normally oviparous (egg-laying) and their development may be either direct or indirect. In the case of indirect development, there is a trochophore or veliger larva stage before changing into an adult.

Do Mollusca reproduce asexually?

Mollusks reproduce sexually, and most species have separate sexes. Sexual reproduction is achieved by the formation and fusion of gametes: sperm and eggs.

Is Mollusca a bilateral symmetry?

The generalized mollusc is bilaterally symmetrical and has a single, "limpet-like" shell on top. The shell is secreted by a mantle covering the upper surface. The underside consists of a single muscular "foot".

How do Mollusca reproduce?

Mollusks are primarily of separate sexes, and the reproductive organs (gonads) are simple. ... Most reproduction, however, is by sexual means. Eggs and sperm are released into the water by members of some (primitive) species, and fertilization occurs there.

What secretes the shell in molluscs?

In shelled molluscs, the mantle is the organ that forms the shell, and adds to the shell to increase its size and strength as the animal grows. Shell material is secreted by the ectodermic (epithelial) cells of the mantle tissue.

Which of the following molluscs are hermaphroditic?

Hermaphroditism occurs in 100% of the Solenogastres, 99% of the Opisthobranchia, 100% of the Pulmonata, 3% of the Prosobranchia and 9% of the Bivalvia. Sequential hermaphroditism, whatever its theoretical advantages over gonochorism, is not common among molluscs.

What are the characteristics of Mollusca that distinguish it from other phyla?

Characteristic Features of Phylum Mollusca

• They are bilaterally symmetrical.
• They are triploblastic, which three layers.
• They show organ system grade of organisation.
• The body is soft and unsegmented.
• Body is divisible into three regions – head, a visceral mass, and ventral foot.
• Body is covered by a mantle and shell.

Are molluscs dioecious and Oviparous?

Molluscs are dioecious, oviparous with indirect development.

Which of the following does a mollusk use for movement?

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.

Which of the following does not belong to phylum Mollusca?

Trematoda do not belong to phylum Mollusca It is a class of phylum Platyhelminthes.

Is Mollusca a radial symmetry?

These creatures are radially symmetrical, meaning all their appendages emanate outward from a central point. Most mollusks, on the other hand, exhibit bilateral symmetry.

Does Mollusca have exoskeleton?

Molluscs are mostly aquatic, and are named from the Latin molluscus, meaning "soft". Their soft bodies are enclosed in a hard shell made of calcium carbonate (CaCO3), which functions as an exoskeleton. This shell is secreted by a thin sheet of tissue called the mantle, which encloses the internal organs like a glove.

What type of symmetry is Mollusca?

Mollusks have bilateral symmetry. – The two halves of the body mirror each other. Gastropods (snails) ~ eat with a radula (tiny tongue covered with teeth.

Which of the following is true about reproduction in Mollusca?

The simplest species of molluscan reproductive system relies on external fertilization. ... Some species of mollusc are hermaphrodites that reproduce by internal fertilization. Therefore, option C both sexual and asexual reproduction is the correct answer. So, option C is the correct option.

How do Mollusca reproduce asexually?

Mollusk reproduce asexually by being hermaphroditic where they are both male and female they also asexually reproduce by budding.

Do all molluscs have a larval stage?

Like many invertebrates, the mollusk life cycle includes one or more juvenile or larval stages that are very different from the adult form of the animal. Both mollusks and annelids develop through a larval stage called a trochophore larva.

Which one of the following phylum is correctly matched with its two general characteristics?

Arthropoda - body divided into head, thorax and abdomen and respiration by mouth.

Which of the following structure in molluscs test the chemical nature of water?

Many molluscs have a water-testing organ present in the mantle cavity. This is called a) Statocyst ...

Which of the following phyla is omnipresent?

Arthropoda is the largest phylum in animal kingdom. There are more arthropods on this earth than humans. They are present everywhere.