Class Polyplacophora:
Class polyplacophora have following characteristics:
Shell:
Chitons have a unique shell structure consisting of eight overlapping plates, also known as valves. These valves provide protection to the soft body parts of the chiton.
Radula:
They possess a radula, which they use to scrape algae and other microscopic organisms from rocks and other surfaces.
Mantle and Girdle:
The mantle of chitons covers the entire dorsal surface of the body and also secretes the shell plates. This mantle is attached to a muscular girdle that encircles the animal and helps to maintain its shape and flexibility.
Foot:
Chitons have a broad, muscular foot that is used for locomotion, enabling chitons to cling tightly to rocks and move slowly along surfaces.
Habitat:
Chitons are primarily marine animals and are found in intertidal zones and shallow coastal waters.
Grazing Feeding:
They are basically herbivores and feed primarily on algae and other plant material found on rocky surfaces.
Protective Adaptations:
When disturbed or threatened, chitons can curl up into a ball, hiding their vulnerable soft body under the hard shell plates. Some chitons can also release bioluminescent chemicals which they use as defense mechanisms.
Limited Mobility:
Chitons can move slowly using their muscular foot. Their mobility is generally limited to crawling along surfaces or navigating within the intertidal zone.
Reproduction:
Chitons are dioecious, meaning they have separate sexes. They reproduce by external fertilization, releasing eggs and sperm into the open water.
Ancient Lineage:
Chitons are considered to be one of the oldest living groups of mollusks because they have retained many primitive features.
Examples of class Polyplacophora:
| Scientific Name | Common Name(s) |
| Acanthochitona spp. | Spiny Chitons |
| Tonicella lineata | Lined Chiton |
| Katharina tunicata | Tortoiseshell Chiton |
| Lepidochitona spp. | Segmented Chitons |
| Nuttallochiton mirandus | Furry Chiton |
| Cryptochiton stelleri | Gumboot Chiton |
| Trachydermon cinereus | Ashy Chiton |
| Tonicella spp. | Smooth Chitons |
| Chiton granosus | Granular Chiton |
| Chiton olivaceus | Olive Chiton |
| Chiton tuberculatus | Tuberculated Chiton |
List of Mollusca classes with examples
Phylum Mollusca is classified into seven major classes namely:
- Class Gastropoda
- Class Bivalvia
- Class Cephalopoda (intelligent marine animals)
- Class Polyplacophora (chitons)
- Class Scaphopoda (tusk shells)
- Class Monoplacophora
- Class Aplacophora (worm-like mollusks)