Class Polyplacophora (chitons
Chiton
A chiton was a form of clothing. There are two forms of chiton, the Doric chiton and the later Ionic chiton.
What is the meaning of polyplacophora?
(poly-plac-o-phor-a (lor-i-cat-a)) Latin meaning: poly = many plac = plate phor = carry, i.e.: bearer of many plates. The polyplacophorans, commonly known as chitons, are often considered by scientists to be the most primitive of all existing molluscs.
What is the economic importance of class Polyplacophora to humans?
Class Polyplacophora is not of significant economic importance to humans in contemporary society, although indigenous people of the Pacific coast of North America are reported to have eaten Cryptochiton stelleri. Kozloff, E. N. 1990. "Class Polyplacophora," pp. 376-382 in Invertebrates.
What is the difference between polyplacophora and Neoloricata?
The class Polyplacophora extends back to the Late Cambrian Period with the early genus Matthevia. Some fossil species had only seven plates. Examples of the order Paleoloricata are found from the Late Cambrian through the Late Cretaceous. The order Neoloricata extends from the present back to the Mississippian Period.
How many pairs of ctenidia do polyplacophorans have?
Polyplacophorans have six to 88 pairs of bipectinate ctenidia, the number of which is typically not species specific, increasing as the individual grows. The ctenidia are arranged in the mantle folds that extend from front to rear along each side of the animal's foot. The sexes are separate.
What is unique about the class Polyplacophora?
Polyplacophorans are a class of the phylum Mollusca and are commonly known as Chitons. They are easily distinguishable from the superficially similar Limpets (which are part of the Gastropoda) by the fact that their shell is composed of eight separate plates, rather than being just one piece.
What is the characteristics of chiton?
Chitons (KI-tons) are flattened mollusks that are egg-shaped in outline. They have eight distinct and overlapping shell plates, or valves, across their backs. The valves are layered, with each layer made up of mostly calcium carbonate. Each valve is usually shaped like a butterfly.
What type of animal is in class Polyplacophora?
marine molluscsChitons (/ˈkaɪtənz/) are marine molluscs of varying size in the class Polyplacophora (/ˌpɒlipləˈkɒfərə/), formerly known as Amphineura. About 940 extant and 430 fossil species are recognized.
Do Polyplacophora have gills?
Contrary to snails, for example, chitons, have no mantle cavity containing gills. Instead, there is a groove running almost all around the animal between mantle and foot containing numerous mollusc-type gills or ctenidia....Chitons (Placophora)ClassSpecies No.Molluscs (Mollusca)55.4009 more rows
What are some examples of Polyplacophora?
ChitonidaNeoloricataAcanthoch...ChitoninaMopaliidaeTonicellidaeChitons/Lower classifications
What is the meaning of Polyplacophora?
Definition of Polyplacophora : an order of Amphineura comprising the chitons all of which have the foot occupying the whole ventral surface of the body and the shell composed of eight calcified dorsal plates.
What features of members of the class Polyplacophora if any would be considered atypical of molluscs in general?
Members of class Polyplacophora are better known as “chitons;” these molluscs have a large foot on the ventral side and a shell composed of eight hard plates on the dorsal side. Class Bivalvia consists of mollusks with two shells held together by a muscle; these include oysters, clams, and mussels.
How many shells do Polyplacophora have?
The polyplacophora. Chitons are the familiar group of organisms that have eight valves on their shells. A visit to any rocky intertidal habitat around the world will introduce one to these beautiful molluscs.
Do Polyplacophora have tentacles?
They have no foot or shell, and the epidermis secretes chitinous scales or spicules. They have no eyes or tentacles, and the radula is either reduced or absent.
Does Polyplacophora have locomotion?
Chitons move by creeping slowly using the muscular foot for locomotion and adhesion, and their separate, articulating valves allow them to move over and cling tightly to sharply curved or irregular surfaces.
How do Polyplacophora respire?
Inside the groove are gills that help the chiton to breathe underwater. Oxygen-carrying water enters the grooves near the head, flows through the gills, and exits at the rear of the body. As the water exits this system, it carries away waste products released from the anus.
Does Polyplacophora have mantle cavity?
The mantle skirt extends around the whole periphery of the animal as a girdle (Polyplacophora-transverse sec.). The ventral surface is mainly occupied by the muscular foot, which is surrounded by the mantle cavity.
How many species of polyplacophorans are there?
Polyplacophorans include about 600 extant species. Entirely marine, they inhabit hard bottoms and rocky coasts in all of the world's oceans. Although commonly intertidal, living chitons have been dredged from waters as deep as 7000 m.
How many plates are there in fossils?
Some fossil species had only seven plates. Examples of the order Paleoloricata are found from the Late Cambrian through the Late Cretaceous. The order Neoloricata extends from the present back to the Mississippian Period. The fossil record of chitons is difficult to assess given the rarity of articulated specimens.
Where do polyplacophora live?
They can also live on rocks. Polyplacophora are found in cold waters and in tropical waters. Some live in tidal zones and can hold up to air exposure for periods of time. Others can live as deep as 20,000 feet under the surface of the water. They are only found in salt water.
How do polyplacophora reproduce?
How Polyplacophora Reproduce. There are male and female chitons, and they reproduce by releasing sperm and eggs into the water. The eggs may be fertilized in the water or the female may retain the eggs, which are then fertilized by sperm that enters along with water as the female respires.
What does polyplacophora mean?
POLYPLACOPHORA. (Alternate name: Loricata) (poly-plac-o-phor-a (lor-i-cat-a)) Latin meaning: poly = many plac = plate phor = carry, i.e.: bearer of many plates. The polyplacophorans, commonly known as chitons, are often considered by scientists to be the most primitive of all existing molluscs. Strictly marine, the majority ...
What tissue covers the margins of each plate?
Except for the posterior edge, a reflexed fold of mantle tissue covers the margins of each plate. In some chitons (such as the genus Amicula), the mantle totally covers the plates. The girdle is very heavy and extends beyond the lateral margins of the plates.
What is the name of the specialized eye cells that penetrate the articulamentum of the shell?
A large pair of pallial visceral nerve chords completes the nerve ring. Some families do have specialized eyes called the aesthetes. These are mantle sensory cells that penetrate the articulamentum of the shell and are lodged within vertical canals leading to the outside of the shell.
