What are examples of Polyplacophora?

What are examples of Polyplacophora?

The majority of chitons have separate sexes. The pair of sexual organs (gonads) usually are grown together forming one organ with two channels leading into the mantle groove….Chitons (Placophora)

Class Species No.
Mussels (Bivalvia) 10.000
Squids (Cephalopoda) 650
Elephant Tusks (Scaphopoda) 600
Neopilina (Tryblidia) 20

How do chitons sense their environment?

The primary sense organs of chitons are the subradular organ and a large number of unique organs called aesthetes. The aesthetes consist of light-sensitive cells just below the surface of the shell, although they are not capable of true vision.

What type of circulatory system do mollusks have?

Mollusks possess an open circulatory system in which body fluid (hemolymph) is transported largely within sinuses devoid of distinct epithelial walls.

How big do chitons get?

About 5 cm (2 inches) is the maximum length of most chitons, but Cryptochiton stelleri, of the Pacific coast of North America, may grow to about 43 cm. Chitons are very flexible and can fit snugly into rock crevices or curl into a ball when detached.

How do you identify a chiton?

Chitons are untorted, bilaterally symmetrical molluscs with a distinct head and a shell composed of a longitudinal series of eight shingle-like, overlapping plates.

Are chitons edible?

Human use. Chiton magnificus is edible. Although relatively uncommon, it is one of the few commercially important chitons in its range, others being the even larger, up to 23 cm (9.1 in), spiny Acanthopleura echinata and the smaller, up to 4.5 cm (1.8 in), brownish Chiton granosus.

Do chitons have a complete gut?

Adults develop radular mouth parts (recurved chitinous teeth stretched over a supportive base). The radula serves as a scraping apparatus. Have a complete gut. Gas Exchange: Mantle cavity forms a groove extending along the body margin, encircling the foot.

How many eyes do chitons have?

1,000 eyes
And chitons have up to 1,000 eyes and can grow more throughout their lifetimes, replacing any that are damaged.

Do molluscs feel pain?

After discussing this framework in detail, we conclude that molluscs are incapable of feeling pain since the nervous system of molluscs (unlike humans) lacks the neural architecture required to implement the requisite computations defined within this framework.

What is the excretory organ of Mollusca?

Complete answer: The excretory organs of Mollusca are metanephridia. A molluscan body is found to be unsegmented. However, they do have a distinct head, a muscular foot, and a visceral hump.

Do chitons have eyes?

Chitons are protected by a shell consisting of eight plates. The plates are dotted with hundreds of small eyes called ocelli. Each one contains a layer of pigment, a retina and a lens.

Do chitons have teeth?

Chitons have several dozen rows of teeth attached to a ribbon-like structure. Each tooth is composed of a mineralized cusp, or pointed area, and base supporting the mineralized cusp. Magnetite is deposited only in the cusp region.

Which is the most advanced mollusc in the world?

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. The gastropods (snails and slugs) are by far the most numerous molluscs and account for 80% of the total classified species.

Which is the only cephalopod that has an external shell?

Nautiluses are the only extant cephalopods with a true external shell. However, all molluscan shells are formed from the ectoderm (outer layer of the embryo); in cuttlefish ( Sepia spp.), for example, an invagination of the ectoderm forms during the embryonic period, resulting in a shell ( cuttlebone) that is internal in the adult.

How did the study of Mollusca get its name?

The study of Mollusca is called Malacology. They are sluggish invertebrates, with a thin fleshy envelope or mantle covering the visceral organs. The term Mollusca was derived from the term given by Aristotle to cuttlefish.

Are there any cephalopods left in the world?

Cephalopods (Phylum Mollusca, Class Cephalopoda) Cephalopods are an exclusively marine group of mollusks that today include squids, cuttlefish, octopi, and the chambered nautilus. Two other important cephalopod groups, the ammonoids and the belemnoids, went extinct at the end of the Cretaceous Period (~65 mya).

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