Chitons are also sometimes commonly called sea cradles and they may also be referred to as loricates, polyplacophorans, and rarely polyplacophores. Chitons have a shell composed of eight separate but clearing shelly plates, which are held together with a structure known as a girdle. Chitons live on hard surfaces such as on or under rocks, or in rock crevices. Some species live quite high in the intertidal zone and are exposed to the air and light for long periods.
Others live subtidally. A few species live in deep water, as deep as 6, m about 20, ft. It is worth pointing out that chitons as a molluscan class are exclusively and fully marine. This is in contrast to the bivalves which were able to adapt to brackish water as well as freshwater, and the gastropods which were able to make successful transitions to freshwater and terrestrial environments.
Chitons have shells made up of eight overlapping calcareous valves held together and surrounded by a girdle. In many species the surface of the girdle is covered in, or decorated with, scales, hair-like protrusions, or glassy bristles.
After a chiton dies, the individual valves which make up the 8-part shell come apart, and may sometimes wash up in beach drift. The individual shelly plates from a chiton are sometimes called "butterfly shells" because of their shape.
Chitons are molluscs and are related to slugs and snails gastropods , mussels and oysters bivalves , and squids and octopuses cephalopods. Within the phylum Mollusca, chitons belong to a distinct group known as the Polyplacophora.
This name refers to the eight separate shell plates, which are embedded in a thick girdle surrounding the body and cover the dorsal surface. Many chiton species are found in the intertidal zone, in shaded depressions or crevices or under rocks on open coast, where they are active at night or at high tide, but they also occur to depths of m or more. Chitons do not have cephalic eyes or tentacles, and the head is located on the underside of the body, anterior to the broad muscular foot.
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. When disturbed, chitons clamp down tightly against the substrate, and then lift the inner margin of the girdle to create a vacuum and hold the animal firmly in place. Dietary Studies at Ahousat and Anaham Reserves. Canadian Journal of Public Health , 62 Emmons GT: Food and Its preparation.
In: The Tlingit Indians. Edited by de Laguna F. Washington, DC: Smithsonian Institute; Special Publication No. Victoria, B. Paper No. Ottawa: National Museums of Canada; Jewitt, Washington, DC: Smithsinian Institution; Nanaimo, B. Jacobs M, Jr. In: Raveu's Bones. Edited by Hope A; Journal of the Washington Academy of Sciences , 38 8 Nutrition Research , 4 Smithsonian Institution Bureau of American Ethnology.
Thirty-Fifth Annual Report. In North America, chitons include two species distributed along the Pacific coast: the black katy chiton Katharina tunicata and the giant Pacific chiton Cryptochiton stelleri.
Chitons have a flat oval shape and a distinctive shell consisting of eight articulated plates or valves bounded by the mantle girdle. On the ventral side, they have a central sucker-like foot they can attach to the substrate surrounded by a row of gills. Most chitons are a few centimeters long, but some, like the giant Pacific chiton can grow up to 30 cm long [1].
Chitons mostly occupy rocky shores, but there are a few deepwater species. They are mostly browsers, scrapping off algae and other encrusting organisms off the substrate with their radula, but some species, like the black katy chiton, are carnivorous and feed on crustaceans and worms.
They have separate sexes and fertilization is external [1]. The black katy chiton Katharina tunicata is a primitive marine mollusk occurring along the North American Pacific coast from Alaska to California.
In black katy chitons, the thick shinny black griddle covers almost all the whitish dorsal plates, except for diamond shapes along a mid-dorsal ridge.
Their underside has a peach colour and their foot is darker orange. They live for around 3 years and generally grow not much bigger than 10 cm long. Black katy chitons safely secure themselves on rocky shores, from the intertidal zones up to 40 m deep, using their sucker-like foot and are able to resist intense wave action.
They first spawn in their second year and southern populations generally spawn in spring, while more northern populations spawn in the summer. Predators of black katy chitons include sea urchins and seabirds [2]. The giant Pacific chiton Cryptochiton stelleri is a primitive marine mollusk occurring along the North American Pacific coast from Alaska to California. In the giant Pacific chiton, individual dorsal plates are undistinguishable being entirely covered by a thick leathery reddish brown mantle and the underside is yellowish orange.
They are the considered the largest chiton and can grow to over 35 cm long and weigh close to 2 kg. Giant Pacific chitons are most often hidden in kelp beds, secured on rocky bottom, from shallow interdidal waters up to around 20 m deep.
They spawn in spring in southern parts of their range and later in the north. Giant Pacific chitons do not have many predators, except for mostly sea snails [3].
In: The Encyclopedia of Underwater Life. Wood, Home Animals Cultures Nutrients Feedback. Black Katy Chiton Tlingit shellfish middens suggest that black katy chitons were frequently eaten; however they were not collected during summer when the risk of shellfish poisoning was high [3]. The Coast Salish collected black katy chitons, which were usually found grouped in the intertidal zone [9, 17].
Women used a prying stick to remove them from the rocks and usually gathered them with other beach food. The black katy chiton was considered a delight, especially by the women who went out to collect them in canoes May and June. When removing black katy chitons from rocks, the Manhousat were very cautious not to damage the tongue, also known as the foot.
If the tongue was impaired during gathering the flesh would become tough. Black chitons that had what looked to be red tongues were the tastiest. The red tongues meant that the gonads were mature and the flesh was ideal to eat [16]. Black katy chitons were consumed raw or cooked with water, steam or fire [3, 16]. Moss [6] reports that the Tlingit may have pickled chitons in vinegar. Regardless of the method of preparation the back plates and internal organs were always removed and discarded [6, 16].
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