Chiton
Tonicella lineata
- Altkäferschnecken ( Palaeoloricata )
- Neukäferschnecken ( Neoloricata )
- Much Platter ( Multiplacophora )
The chitons ( Polyplacophora ) are a group of molluscs or the subgroup of spiked molluscs represents the approximately 900 species of chitons live exclusively in the sea, especially in the area around Australia. You can reach heights between 0,5 and 45 cm and are crepuscular. The age of the mollusc group is estimated at 500 million years.
Features
The main characteristic of the Polyplacophora is its shell, which is at the present forms of eight individual plates and covers the top of the animal. For fossil forms are up to 17 individual plates known ( Much Platter = Multiplacophora ). The characteristic shell plates are mutually movably connected and framed in its entirety by a belt ( Perinotum ). In girdle spicules, Kalkschüppchen or Kalkkörperchen are incorporated. The plates cover the head and only by a groove remote from the head crawling foot of the animals. A sheath channel with up to 88 pairs of gills surrounding the head and the foot. The dorsally located, upper, pigmented, composed of organic material layer of the skin is called the tegmentum The plate is covered with hundreds of tiny eye lenses made of crystal ( aragonite ), under which put light-sensitive cells. Thus, the animals can probably locate the outline of her enemies. Aragonite has two focal lengths, so the animals can see clearly equally under water as on the sea surface.
Way of life
Chitons eat mostly plant and animal nursery substrate - algae, bryozoans, hydroids and barnacles ( Balanidae ). The mouth opening with the very large radula ( rasping tongue ) is located directly in front of the crawling foot of the animals. The rasp can reach a length of up to one third of the body length and is equipped with sometimes more than 40 transverse rows by magnetite hardened teeth. However, some species also feed on prey on small crabs and come in depths up to 5000 m before. The animals lurking for prey by lifting the front part of the body or of the belt from the ground. Small tentacle- like extensions at the leading edge of the mantle act as Tastsinnesorgane. If a prey animal with tentacles in contact, then folds the belt to the ground, burying the prey among themselves. The prey can be eaten in peace.
Most chitons are dioecious and gametes (sperm and eggs) are easily discharged into the water. Only a few species takes place internal fertilization. Some species even practice a primitive form of parental care in its sheath gutter.
Nomenclature of chitons
The following classification follows Parker:
- Class Polyplacophora Subclass Neoloricata order Lepidopleurida Family Hanleyidae
- Family Choriplacidae
- Family Lepidopleuridae
- Family Subterenochitonidae
- Family Ischnochitonidae genus Lepidochitona Knurled Chiton ( Lepidochitona cinerea)
- Genus chiton chiton olivaceus
- Family Acanthochitonidae
- † family Mattheviidae
- † family Chelodidae
- † family Septemchitonidae
- † family Preacanthochitonidae
- † family Gotlandochitonidae
- † family Scanochitonidae