Kamis, 18 Agustus 2011

How do clams reproduce?

: oysters bivalves procreate

Why: On reddit, Oyster eggs:

Answer: Bivalves (clams, cockles, mussels, oysters, scallops, etc.) reproduce by external fertilization!

Marine bivalves reproduce by releasing prodigious numbers of eggs and sperm into the water, where external fertilization occurs. The fertilized eggs then float in the surface plankton.

Within 48 hours after fertilization, the embryo develops into a minute, planktonic, trochophore larvae. This stage is followed by another larval form, the veliger, which settles to the seabed and transforms into an adult.

In freshwater bivalves, the eggs are retained in the gill chambers of the female, where they undergo fertilization and develop into a peculiar larval form, the glochidium.

Upon its release, the larva attaches to passing fish, and lives as an ectoparasite for several weeks before settling.
Oyster eggs are commonly sold as food for coral in saltwater aquariums.

: Science

The More You Know: But how do pearls form? First, anatomy:

Then (from HowStuffWorks):

As the oyster grows in size, its shell must also grow. The mantle is an organ that produces the oyster's shell, using minerals from the oyster's food. The material created by the mantle is called nacre. Nacre lines the inside of the shell.

­The formation of a natural pearl begins when a foreign substance slips into the oyster between the mantle and the shell, which irritate­s the mantle. It's kind of like the oyster getting a splinter. The oyster's natural reaction is to cover up that irritant to protect itself. The man­tle covers the irritant with layers of the same nacre substance that is used to create the shell. This eventually forms a pearl.

So a pearl is a foreign substance covered with layers of nacre. Most pearls that we see in jewelry stores are nicely rounded objects, which are the most valuable ones. Not all pearls turn out so well. Some pearls form in an uneven shape -- these are called baroque pearls. Pearls, as you've probably noticed, come in a variety of various colors, including white, black, gray, red, blue and green.

So basically, pearls are cysts that the oysters make to protect themselves from foreign objects. Some farmers even irritate their oysters on purpose to create "cultured pearls"!

Fun fact: Oysters are among the only frutti di mare that I don't eat.

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