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As a child I watched tiny fiddler crabs living in conical shells, and many years later I find that people study fossil turritellids. So now I wonder: how old are shells, typically, that you see on beaches? Do they wear out after a year of sand abrasion? 100 years, a million? Is it known?
Mollusk shells found on typical east coast (US) beaches can range from days old (the animal that made the shell died recently) to thousands of years old. Some shells in our state, North Carolina, have been dated as 40,000 years old. A high number of "seashells" found on east coast beaches are from mollusks that lived in the marsh on the back side of the island. The presence of these shells on ocean beaches provides evidence of island migration - the island has moved landward over the marsh until what was once the marsh is now the ocean shore. Once buried in the sand, the shell is well preserved until erosion uncovers it. Occasionally, fossilized shells are washed up on beaches after having been dislodged from offshore limestone deposits - these shells can be millions of years old.
-Richard - Carolina Ocean Studies
Ages of shell as a piece can be checked or counted.
1) Examine the shell's ridges with a magnifying glass.
2) Tabulate the number of ridges. You can approximate by number of cell per unit length.
3) Divide the total number of ridges by 365. Each day the little mollusk earns a new ridge, thus total will give you its age.
But, that is age of one shell. If you are asking the age of all of them in a beach, my guess would be as old as the beach.
Read more : http://www.ehow.com/how_6331956_tell-age-seashell.html
Should You Take a Conch Shell From the Beach?
If you've ever held a beautiful conch shell up to your ear to "hear" the ocean, you might have thought that's where the conch experience begins and ends. In reality, that's only a tiny glimpse into the story of this beloved marine animal. Because although some people know that an animal once inhabited such shells, few are aware of just how complex the conch's development is, not to mention that it's teetering on the brink of existence.
What Is Conch?
Although there are a number of species, the most well-known is undoubtedly the Strombus gigas or queen conch (pronounced "konk.") It's commonly recognized by the trademark large, spiral-shaped shell, which is typically either pale pink or orange in the interior. Inside a living conch shell is a mollusk, or soft-bodied sea snail. Conchs get around by using a foot or horn to drag themselves along the seafloor.
The entire animal is extremely valuable. "The top of the shell is often cut off and used as a horn for signaling," emails Martha Davis, director of Community Conch, a nonprofit conservation organization working to preserve conch in the Bahamas. "Conch are prized not only for their shell but also for their meat. For centuries they have been used as a subsistence food throughout the Caribbean."
Shell collectors prize them as well for their beauty, adds Dr. Ana Carolina Peralta Brichtova, a professor at Universidad Simon Bolivar in Caracas, Venezuela. "Historically, Strombus gigas has been a highly prized species because indigenous pre-Columbian civilization used their meat for food, and the shells for ornaments, horns and trading."
Conch are native to such picturesque habitats as the Bahamas, Bermuda, the Florida Keys and the U.S. Virgin Islands, Jamaica and other Caribbean islands. Some species also live off the coast of South America and the Mediterranean. Conchs mate when a male and female are in proximity to each other, resulting in an egg mass of roughly 400,000 eggs, according to Davis. "The eggs hatch after about five days and then float on the currents for about three weeks until settling in a favorable habitat," Davis says. The queen conch, when allowed to really hit its stride, can live up to 40 years! Its development is slow, but steady, taking several years:
- Year 1: Conch bury themselves in the sand.
- Year 2: They emerge from the sand, but are extra vulnerable to predators, like turtles and sharks.
- Year 3: They have grown in length and developed a thick shell, which helps keep them safe from predators.
- Years 4 to 5: They achieve sexual maturity and can reproduce.
"This slow rate of maturing makes them vulnerable to fishers who think they are mature because they are big in length," Davis says. "Paper thin lips are a signal that the conch is not sexually mature." A fully mature adult conch sports a large shell festooned with spines. Its shell forms a thick flaring lip. That's the main way to distinguish between juvenile and grown conchs.
Why Conchs Are in Trouble
The conch's status as a tasty delicacy (not to mention its collectible shell) makes it at risk for overfishing, a fact compounded by the fine distinction between the thin-lipped juvenile (which should not be fished) and the thicker-lipped adult.
The main problem, Davis notes, is that harvest criteria are woefully out of date and do not reflect more recent science determining that the lip thickness needs to be 15 millimeters (about a half-inch) before maturity is reached (again, around age 4 or 5). "Most conch are harvested long before that age and so the populations have been declining because they have not had a chance to reproduce," she explains. "If too many conchs are harvested in an area, and the numbers decline, they will not be able to find each other to mate."
Conchs are already depleted in areas where they were once populous, especially in the Florida Keys where harvesting was banned decades ago and yet populations still haven't recovered. In parts of the Caribbean, rules have been put into place to curb overfishing. But it's still a major problem, due to lack of rule enforcement, cross-border poaching and a great demand for conch as an export, according to Davis.
Other problems have to do with the world at large. "The ocean is experiencing loss of habitat due to climate change or chemical contamination, those being additional threats for these organisms," explains Peralta Brichtova. "Strombus gigas is on the CITES list and also the [International Union for Conservation of Nature] is paying special attention to its status." CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora considers conch as "currently not threatened with extinction, may become so without trade controls."
Reversing the Conch Catastrophe
Conchs are vital to the ocean both as herbivorous consumers and prey. "When naturally large populations of conch occur in nursery grounds, they serve to keep seagrass meadows healthy by removing excess algae and organic detritus that can inhibit seagrass growth," Davis says. "Also, small conch provide an important food source for a very long list of invertebrates such as shrimp, crabs and lobsters, as well as dozens of fish species and sea turtles."
As previously mentioned, the Florida Keys suspended its conch harvesting industry in the 1980s and implemented marine preserves in an effort to help the population rebound. So far, it's failed to do the trick. So, experts are turning to strict recommendations to keep the Caribbean from winding up in Florida's shoes. In fact, Davis says that the Bahamas reduced export of conch in 2019, with plans to phase it out completely by 2024.
Throughout much of the Caribbean, however, the advice is inconsistently heeded. "Some countries have not changed out of date harvest rules. Some countries have all the needed rules but there is no enforcement," Davis notes. "The more progressive countries set quotas or limits and stop fishing when that limit is reached however this is not always successful in stopping the decline of mature conch."
Should You Take Home a Conch Shell?
If you've read this far, we think you know the answer: Leave it alone, unless you are sure there is no animal inside it. People have been jailed in Florida for taking a live conch from the beach or the ocean. "It is illegal to fish for conch in Florida and to bring shells into the U.S. from the Bahamas," says Davis. "[It's] best to eat conch from a live stand where you can see that the conch you are eating has a thick lip and therefore time to reproduce."
You're not really hearing the ocean when you hold a conch shell up to your ear. The sound is actually the ambient noise around you. Conch shells are good at amplifying noise.
Seashell fossils are formed when a sea animal with a shell dies and their body and shell begin to decompose. Seashell fossils are more common than other fossils because the shell is hard and therefore more likely to be preserved, compared to organisms with only soft tissue. Animals without a shell or bones hardly ever become fossilized.
Sea fossils, along with all fossils found, are actually quite rare as it takes so long for an organism to decompose and leave an impression on a rock. By the time this process is complete, the remains could have easily been moved by natural forces or by other animals. That's one of the reasons why fossils are so special. The oldest fossil, according to Astronomy.com, is captured on a 3.5-billion-year-old rock from Western Australia.
How to Tell the Age of a Seashell
Seashells can continue to grow throughout the life of the creature inhabiting them, which can be a long time--Bangor University found evidence of a 400-year-old clam. Scientists have established methods to determine the life span of certain mollusks residing in shells, which can help anyone in determining the approximate age of a shell.
Examine the shell's ridges with a magnifying glass. According to Banque des Savoirs, a science and research site, these ridges can be an accurate indicator of age, especially in scallops, which produce about one ridge per day.
Tabulate the number of ridges. If the number is too high to count, you can estimate by counting a group of 100 ridges and then measuring the approximate width of the area that the ridges occupy. Measure the total width of the shell, and then divide it by the ridges width. Multiply this number by 100 to estimate the total number of ridges.
Divide the total number of ridges by 365. Because scallops produce about a ridge per day, dividing by 365 will give you the approximate age of the scallop, before it died or abandoned the shell, in years.
It won't give you the exact age of the shell, since the shell theoretically could have floated around for years afterward, but it is unlikely that the shell lasted more than a few months after the death of the animal before it was either destroyed or covered with layers of sand, on its way to becoming a fossil, according to Terra Daily, a nature publication.
Things You'll Need
This method works best with scallops, which have visible, easily defined ridges, but the technique can work for estimating other shellfish as well. Oysters are the most difficult to identify with because the shells are smooth, with difficult to discern ridges. In this case, scientists must use chemical analysis of the minerals in the shells to try to estimate age.
Ocean Science Activities
Children use a funnel to pour a cup full of baby oil (or cooking oil) into a clear plastic bottle. They fill the bottle the rest of the way with water. We give the liquid a chance to settle, then add a few drops of blue food coloring. It’s fun to watch the blue as it drops through the oil and “explodes” into the water. Last, we add plastic “fish” (sequins), and make waves by turning the bottle sideways and rocking it gently.
FORAM FACTS ANINTRODUCTION TO FORAMINIFERA
Fully grown individuals range in size from about 100 micrometers to almost 20 centimeters long. Some have a symbiotic relationship with algae, which they "farm" inside their shells. Other species eat foods ranging from dissolved organic molecules, bacteria, diatoms and other single-celled algae, to small animals such as copepods. They catch their food with a network of thin pseudopodia (called reticulopodia) that extend from one or more apertures in the shell. Benthic (bottom-dwelling) foraminifera also use their pseudopodia for locomotion.
WHERE DO THEY LIVE?
There are an estimated 4,000 species living in the world's oceans today. Of these, 40 species are planktonic, that is they float in the water. The remainder live on or in the sand, mud, rocks and plants at the bottom of the ocean. Foraminifera are found in all marine environments, from the intertidal to the deepest ocean trenches, and from the tropics to the poles, but species of foraminifera can be very particular about the environmentin which they live. Some are abundant only in the deep ocean, others are found only on coral reefs, and still other species live only in brackish estuaries or intertidal salt marshes.
Foraminifera are among the most abundant shelled organisms in many marine environments. A cubic centimeter of sediment may hold hundreds of living individuals, and many more dead shells. In some environments their shells are an important component of the sediment. For example, the pink sands of some Bermuda beaches get much of their color from the pink to red-colored shells of a foraminiferan. In regions of the deep ocean far from land the bottom is often made up almost entirely of the shells of planktonic species.
WHY ARE THEY IMPORTANT?
The study of fossil foraminifera has many applications beyond expanding our knowledge of the diversity of life. Fossil foraminifera are useful in biostratigraphy, paleoecology, paleobiogeography, and oil exploration.
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PALEOECOLOGY AND PALEOBIOGEOGRAPHY
The chemistry of the shell is useful because it reflects the chemistry of the water in which it grew. For example, the ratio of stable oxygen isotopes depends on the water temperature, because warmer water tends to evaporate off more of the lighter isotopes. Measurement of stable oxygen isotopes in planktonic and benthic foram shells from hundreds of deep-sea cores worldwide have been used to map past surface and bottom water temperatures. This data helps us understand how climate and ocean currents have changed in the past and may change in the future.
BIOLOGY OF FORAMINIFERA
CLASSIFICATION OF FORAMINIFERA
Chamber arrangements commonly found in living species are shown in figures 1-6. The following terms are used: Unilocular refers to a shell made of a single chamber Uniserial refers to chambers added in a single linear series Biserial refers to chambers added in a double linear series Triserial refers to chambers added in a triple linear series Planispiral refers to chambers added in a coil within a single plane like the chambered nautilus Trochospiral refers to chambers added in a coil that forms a spire like a snail shell Milioline refers to an arrangement where each chamber stretches the full length of the shell and each successive chamber is placed at an angle of up to 180 degrees from the previous, relative to the central axis of the shell Arborescent refers to an erect, branching series of tubes. Terms such as planispiral-to-biserial and biserial-to-uniserial are used when the mode of chamber addition changes during growth.
Of the various kinds of wall composition and microstructure found in foraminifera, three basic types are common among living species. Agglutinated shells may be composed of very small particles cemented together and have a very smooth surface, or may be made of larger particles and have a rough surface. Hyaline shells are made of interlocking microcrystals of CaCO3, and typically have a glassy appearance and pores that penetrate the wall. Porcelaneous shell walls are composed of microscopic rod-shaped crystals of CaCO3. These have a milky, translucent to opaque look and generally lack pores beyond the initial chambers. In some porcelaneous species, small depressions in the surface ornamentation give the appearance of pores. Another type of wall structure, called microgranular, is made of tightly packed equidimensional rounded grains of calcite. This wall type is found in many Paleozoic foraminifera including the fusulinids.
We love visiting the ocean and have the good fortune to be able to go each year! Even if you don’t have the chance to get to the beach you can still have fun with beach and ocean theme activities at home or in the classroom.
We love to share simple science activities that young kids can really get their hands on and enjoy. Our favorite ocean science activities also include many hands-on playful projects as well! Our science activities are usually simple to set up, inexpensive, and easy for anyone to share with kids!
The skeletons of turtles, horses, humans, birds, and bats are strikingly similar, in spite of the different ways of life of these animals and the diversity of their environments. The correspondence, bone by bone, can easily be seen not only in the limbs but also in every other part of the body. From a purely practical point of view, it is incomprehensible that a turtle should swim, a horse run, a person write, and a bird or a bat fly with forelimb structures built of the same bones. An engineer could design better limbs in each case. But if it is accepted that all of these skeletons inherited their structures from a common ancestor and became modified only as they adapted to different ways of life, the similarity of their structures makes sense.
Comparative anatomy investigates the homologies, or inherited similarities, among organisms in bone structure and in other parts of the body. The correspondence of structures is typically very close among some organisms—the different varieties of songbirds, for instance—but becomes less so as the organisms being compared are less closely related in their evolutionary history. The similarities are less between mammals and birds than they are among mammals, and they are still less between mammals and fishes. Similarities in structure, therefore, not only manifest evolution but also help to reconstruct the phylogeny, or evolutionary history, of organisms.
Comparative anatomy also reveals why most organismic structures are not perfect. Like the forelimbs of turtles, horses, humans, birds, and bats, an organism’s body parts are less than perfectly adapted because they are modified from an inherited structure rather than designed from completely “raw” materials for a specific purpose. The imperfection of structures is evidence for evolution and against antievolutionist arguments that invoke intelligent design (see below Intelligent design and its critics).
Even though their name implies that these little guys are bugs, they're not actually insects, but crustaceans. They're in the isopod (meaning same pod or foot) family and have seven pairs of legs that are all similar in size and shape. Roly-poly bugs also have three main body parts – head, thorax and abdomen – as well as simple eyes, uropods, a pair of prominent antennae, gills and lunglike adaptations. As terrestrial creatures related to marine animals, they need moisture to survive but cannot live submerged in water.
Distribution and abundance
Of the more than 65,000 species, about 30,000 are marine, 5,000 live in fresh water, and 30,000 live on land. In general, oceanic gastropods are most diverse in number of species and in variety of shell structures in tropical waters several hundred species (each represented by a small number of individuals) can be found in a single coral reef habitat. This is in contrast to the Arctic or subarctic coasts, where the few species present are represented by many individuals. A number of deep-sea species are known, and a significant snail fauna is associated with hydrothermal vents. Most marine species have large ranges.
Freshwater snails are common in ponds, streams, marshes, and lakes. Usually only a few species are found at one place, but each species will have a rather wide range. Most species are common and feed on algae or dead plant matter. In a few relatively old river systems and lakes—in particular, Lake Baikal in Siberia, Lake Titicaca in South America, Lake Ohrid on the North Macedonia–Albania border, the Mekong basin in Southeast Asia, and the African Rift lakes—extensive and complex radiations of snails have occurred in recent geologic time, producing a large number of species.
Land snails are marginally, but very successfully, terrestrial. When actively moving, they continuously lose water. During periods when water is unavailable, they retreat into their shells and remain inactive until conditions improve. They hibernate during winter periods, when water is locked into snow or ice, and estivate during periods of summer drought. Land snails have been found above the snow line species of Vitrina crawl on snowbanks in Alpine meadows. Other species inhabit barren deserts where they must remain inactive for years between rains.
Fewer than 10 species live in the same area together across most of North America. On the other hand, in such favourable areas as New Zealand, Jamaica, northeastern India, and the wet forests of Queensland (Australia) 30 to 40 different species can be found together. In some parts of western Europe 20 species can be found together. Only one or two species are found in many desert regions, and they have dramatic feeding specializations.
The local abundance of snails and slugs can be spectacular. Millions of some brackish-water and freshwater species can live on small mud flats. An acre of British farmland may hold 250,000 slugs, and a Panamanian montane forest was estimated to have 7,500,000 land snails per acre. Despite this abundance, snails and slugs often pass unobserved. Land and freshwater species often stay hidden during the day and are active at night. Most marine species as well are nocturnal, and the shells of many of these species are so heavily covered with algae and other encrusting organisms that they may be mistaken for bits of rock.