But, CaCO3 is white in color. The colors we see in seashells are often caused by impurities and waste from the organism captured in the shell when it is formed. Coloration is dictated mostly by diet and the water environment the creature lives in. For example, cowries that live and feed on coral, have shells that take on the same hues as the coral.
This natural chemical reaction also helps to protect them from predators by allowing them to blend in with their environment. What about all those iridescent shells that are multicolored and shiny? There's a different process that creates that effect. This iridescence is called mother-of-pearl and is caused by a coating of nacre on the shells. The nacre is secreted by oysters and some other mollusks to protect their bodies from parasites and disease.
The nacre coating is very thin, in the range of several hundred nanometers thick, but is very strong and resilient. These are the foraminifera affectionately known as forams and are present in ocean sediments, the ocean water column and other aquatic environments.
All in all, there are over 50, foram species—10, living and another 40, documented within the fossil record. Of the living species, only around 40 species live within the water column and the rest live within the sediments of the sea or lake, or river bed.
Another important shell-maker in the ocean that is extremely important to the global carbon cycle are coccolithophores. These guys are actually single-celled plants. Individual plates are around three one-thousandths of a millimetre in diameter. And to complete the trifecta of tiny, we have ostracods. These are tiny crustaceans that also form a calcite shell. There are around 70, known species of ostracods, 13, of which are still living, the others found only in the fossil record.
Ostracods are found in both marine and freshwater environments. Just as bigger shells can record environmental conditions in the structure and chemistry of their shells, so do foraminfera, coccolithophores and ostracods. Other shells that are important in the fossil record are brachiopods. There are still some species of brachiopods that exist today, but not many—they have largely been out-competed through geological history by the mollusc species that are common today.
They are extensive in the fossil record though, and their shells can also provide important climate information. Shellfish have been an important part of the Hominin diet for more than a million years. Homo erectus in Trinil, Java, H. So we can thank shellfish for not only providing a record of climatic history within their shells, but also for enabling us to be smart enough to figure it out!
All in all, the diversity in size, shape and colouring of the shells is nothing short of amazing, and quite a few mysteries remain regarding the mechanics of exactly how these animals create their strong, lightweight and durable homes.
She sells sea shells… Expert reviewers. The weird and wonderful world of shells. Image source: Jessica Reeves Most treasured keepsake ever. What is a shell made of? From left: Comparison of form, molecular structure and crystal shape of calcite and aragonite. How are shells built?
A photomicrograph of shell structures. The mechanism that controls the creation of shells is still a mystery. All different shapes… There are lots of different species of snails and shellfish, so it stands to reason that there are lots of different shapes and sizes of shells!
An array of different shell types washed up on the shore. COLOURS As for the stripes that were on my little googly-eyed shell friend, most shell colourings are caused by pigments incorporated into the calcium carbonate shell, or within the periostracum. Natural colour pigment of shells. Microscopic image of forams. When a mollusk dies, it leaves its shell behind. But even after the life of the mollusk inside has ended, its shell is important.
Seashells provide shelter for fish and hermit crabs, nest material for birds, and even nutrients for other animals to build their own shells. The way the shell forms helps explain where the color comes from. For example, seashells from warm waters tend to be more colorful than those from cold areas. This might have to do with their diet. Warm Caribbean waters have more colorful foods than the cold ocean near Maine. Search for:. Videos Activities Podcasts. And why are they different colors?
Can seashells live or die?
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