About Seashells

Walk down any beach (especially right after high tide) and you'll see the discarded exoskeleton of many a mollusk and invertebrate. Not all of them are exoskeletons in reality (crabs and lobsters shed a cartilage material that isn't the same as a mollusk's shell), but all of them are interesting, and most importantly, incredibly unique. Here are some things to think about on your next walk for seashells down by the sea shore.

Significance

The existence of seashells on the beach means that sea life that once inhabited the shell has died or abandoned the shell. For example, predators like seagulls will often catch a shell and smash it on the rocks to eat the sea life within, leaving the sea shell discarded near rocks or on the beach. Sea shells purchased commercially most likely come from sea creatures that have been farmed and harvested for their shells.

Types

There are three types of shells commonly found in nature. They are all exoskeletons, a hard outer surface that has grown and developed on the marine life inside of it. These are referred to as mollusks, and there are several types of mollusks, including: bivalves, for example, clams; scaphopods, for example, tusk shells; or gastropods, for example, snails.
Bivalves are often round or oval and develop length more than width in a radial fashion (not all bivalves are rounded; for example, razor clams develop in length like tusk shells yet are bivalves not scaphopods). Tusk shells are shaped like small elephant tusks and are open at either end to take food in. Gastropods can develop in many different shapes, but often there is some element of a spiral growth, like nautilus shells or conch shells. One of the most beautiful and unbelievable shells in nature comes from the Giant Clam, which can grow up to 4 feet long and weigh as much as 440 pounds. These shells have been used to make bowls, washstands, and where possible, bathtubs.

Function

Shells have two marine uses. The first is as a primary exoskeleton for the marine life within; the creature cannot survive without the shell and grows the shell itself. The second is like a recycled shell--despite the fact that the creature that grew the shell has died, it has been reused by another animal. For example, hermit crabs will actively inhabit the discarded shells of a gastropod until they outgrow it and have to move on. Once discarded from the ocean, many people collect shels and use them as mementos or home decor.

Effects

Seashells are a beautiful reminder of marine life, and when picked up off the beach, collecting them is a harmless and enjoyable pastime. The problem is, however, with shells being a marketable good, there are a lot of species that are farmed and killed to make jewelry and decorations without using the meat within for food or any other purpose (a practice which many ethically disagree with, but does not actually disrupt the natural food chain). Alternatively (and much worse) they are fished from the ocean in large quantities and killed. It's wasteful and, when they aren't grown in farms but fished from the ocean, such mass destruction of sealife is environmentally destabilizing; they are an integral part of the oceanic food chain.

Benefits

Aside from the problem of farming and harvesting shells, seashells become part of a wonderfully symbiotic cycle of life. The shells grow with the creature within them. When the creature within falls prey to predators or scavengers, the shells are discarded either to be reused to grow a hermit crab or equally opportunistic crustacean, or they are washed up and people repurpose them for home decorations, useful items, and jewelry.