Class-Polyplacophora

= = __Class Polyplacophora The Plate Bearers__

The Polyplacophorans, commonly known as the chitons, are primitive mollusks with a fascinating body structure. They have a shelled back consisting of eight small plates, called valves, overlapping each other; a structure called the girdle surrounds the plates. The word "polyplacophora" comes from the Greek terms "poly-", meaning "many"; "plako-" meaning "tablet"; and "-phoros" meaning "bearing".  __The Chitons:__ Tonicella lineata (the linen chiton)

__Tonicella lineata__: the linen chiton is a very colorful mollusk, having blue, purple, and black lines across its back. What's interesting about this chiton is that its mature size is only about five centimeters. The linen chiton usually hangs around the western U.S. coast, from Alaska down to California; some are also found near Japan and Russia.

__LIFE STYLE:__ __Locomotion__ Chitons have a single foot to move about in the water, and/or to cling to rocks to capture prey. __Feeding__ A chiton has a tongue-like structure called the radula, which is used to scrape food such as algae off their substrate (which is the rock where they cling on). Chitons also feed on bacteria, bryozoans (tiny aquatic invertebrates), and some diatoms. __Reproduction__ Chitons are separated into males and females, and the sperm and eggs fertilize as gametes do. Eggs have a spiny outer coat for protection, and the chiton larva is released in time. When the larva is ready for maturity, the body lengthens and the shell plates are formed via glands. Interestingly, teen chitons have a pair of eyes, which they lose upon reaching adulthood. An adult chiton has sense organs called aesthetes, which detect light.

__Fun Facts__ -The fossil record states that chitons have a history going back to 400 million years- around 170 years before the first dinosaurs! -Chitons can curl up into a ball to protect its underside, much like armadillos do, if they are attacked or knocked off their substrates. -A Chiton's shell is made of aragonite (a carbonate mineral), and the plates fall off the chiton upon death.