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How does an oyster make a pearl?

November 12, 2008 by Leave a Comment
Chargrilled oysters

Image via Wikipedia

Oysters are another bivalve animal. In the case of all bivalves, the part of the animal that lines the shell is known as the nacre and the part of the animal that make up the outer shell is known as the mantle. A pearl is created rather by accident when something foreign gets stuck inside the mantle, thus the nacre builds up to protect the animal. This build up is known as the pearl.

Oysters, mussels, and clams all make pearls. However, they are most often seen in oysters. My theory is that the oyster shells are typically not as uniform in shape as clams and mussels and tend to grow according to their surroundings, making it easier for foreign junk to accumulate.

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Why are there holes through some clam shells?

November 7, 2008 by 8 Comments

moonsnailholezd2The shell to the right with a hole through it was hinged to another shell of equal size with an animal living inside (in this case, a clam). Animals with two shells hinged together are known as bivalves. Often, in restaurants oysters and clams are shucked and served “on-the-half-shell” (Yum! I prefer them plain, but sometimes mix it up with ones with plenty of horseradish!).

Animals in the ocean do not have the luxury of someone shucking their prey, but rather use an adaptation called a radula. A radula is the sharp, drill-like tongue of some mollusks (e.g., whelk or conch). Radulas are found on every class of mollusk except for bivalves. A whelk or a conch would use their radula to drill into the clam and then slurp out its meal … Leaving behind a perfectly symmetrical hole. Moon snails and oyster drills are also well-known for using this technique to drill into clams for a feast.

Image (c) imageshack.us

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What lives in the spooky burrows on the beach?

October 19, 2008 by Leave a Comment

The answer is appropriate for this time of year … those quarter-sized holes are the home the ghost crabs or fiddler crabs. Ghost crabs emerge to scavenger upon anything they can get including crabs or clams, bugs or insects, plants or dead stuff (detritus). The burrows are personal territories (i.e., not colonies like on Meerkat Manor). If one male tries to challenge another for his home what occurs is an interesting ritualistic “dance.” There is rarely actual contact and the better “dancer” wins. If you’re tanning on a beach blanket and hear tapping or bubbling noises under the sand, that’s the ghost crab either using their claws for digging or sounds from their gills as they breath. The burrows can be up to three feet deep.

ghostCrab

F1.mediumTop – Ghost crab burrow image (c) aquaessence.com, bottom – fiddler crab burrow image (c) jeb.biologists.org

Filed Under: Animal Homes, Crustaceans Tagged With: ,

Are spider crabs harmful?

October 19, 2008 by 3 Comments

Great question as Halloween approaches!

Common spider crabs, or sometimes called mud crabs, are harmless. In fact, their shells are covered with fine short hairs. When you (if you) attempt to pick one up they would actually feel as though their body was covered in felt.

The short little hairs are really what helps the spider crab survive. They help attach pieces of seaweed or other algae species, sponges or barnacles which aid in its main defense mechanism: camouflage.

These common spider crabs are found along the Atlantic coast from Nova Scotia to the Gulf of Mexico.

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Filed Under: Crustaceans Tagged With: ,

What are the nubby little things on pilings near the beach?

September 30, 2008 by Leave a Comment

Most likely, acorn barnacles.


Let me guess, they look like tiny volcanoes? And they hurt if you rub up against them?barnacles1
That is the outer shell made of calcium. They put this protective layer up when they are not under water.
When it is hide tide the acorn barnacle opens up the volcanoes structure and extends tiny little legs (cirri) all about to gather food circulating in the ocean water.
If you have digested this correctly, you now know the acorn barnacle finds a suitable spot once it is “an adult” and stays there for THE REST OF THEIR LIFE. gulp.

Image (c) uksafari.com.

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More reasons why I love the Atlantic Horseshoe Crab…

September 11, 2008 by 3 Comments

As I mentioned before, the horseshoe crab is a rather frightening looking creature, however quite the opposite is true, they are the steadfast, strong member of the ocean community. This animal, not only is a vital part of the Atlantic coast food chain, but has remained rather unchanged since before the time of the dinosaurs!

An animal that has been in existence since before the dinosaurs is quite impressive and the main reason I have gotten my 4 year old nephew to learn and love saying the scientific name for the Atlantic Horseshoe Crab, Limulus polyphemus. The “polly-femus” part always cracks him up.

But, seriously, they have remained relatively unchanged and evolved little in 260 million years!

How have they managed this impressive feat?

First of all, it is very difficult for predators to get overturn their tough curved shell and get into the crux of their underbelly!

Secondly, they can go a year without food!

Lastly, they are adaptable and can endure the harshest conditions (temperature and ocean salt levels)!

But we’ve only scratched the surface here. Check back often at beachchairscientist.com for more insight about your favorite beach discoveries.

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What eats sea urchins?

September 10, 2008 by 7 Comments
Sea Urchin (Diadematidae) (20 cm)

Image by CybersamX via Flickr

The spines of the sea urchins are there for protection but that doesn’t stop the sea urchin from having enemies. 

For instance, sea gulls love to grab them at low tide at pick away at them high upon the rocks. Crabs have a feast with the urchins by picking away at their spine to get to the inside flesh. Also, urchins that are found along the ocean floor are preyed upon by rays, sharks, seals, and even otters.

But we’ve only scratched the surface here. Check back often at www.beachchairscientist.com for more insight about your favorite beach discoveries.

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How do you know the difference between a male and female blue crab?

September 10, 2008 by 2 Comments

You must be brave enough to pinch the body of the blue crab from behind and lift it upside down (It hurts a lot if they pinch you!).

Male blue crabs have a distinct shape like a pencil – or the Washington Monument – in the center of their bellies. Female blue crabs, on the other hand, have a shape like the Capitol.

http://treadoutdoors.blogspot.com/2012/10/my-husband-gave-me-crabs.html

http://treadoutdoors.blogspot.com/2012/10/my-husband-gave-me-crabs.html

 

 

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What are those sand flea thingees and why do they follow me home?

August 4, 2008 by Leave a Comment

I have two answers for you here – Mole Crabs or Sand Hoppers.

Mole Crabs:

Unfortunately, not all crabs are as interesting in appearance or function as the great Atlantic Horseshoe Crab, but the mole crab has some merit.

Mole Crabs, or one type of sand fleas thingees, are properly referred to as Emerita analoga. A pretty dignified, but boring sounding Latin name – rather appropriate for the critters too.

Here is why:

  • They look like tiny lobsters, but are more closely linked to hermit crabs.
  • At low tide they are quite the efficient tunnelers and use their back legs to dig down to six inches and wait for the next high tide.

Sand Hoppers:

These little guys truly are harmless. Sand hoppers, or the other type of sand flea thingees, are properly referred to as Orchestia. They are most often found in clumps of rotting seaweed – which they eat. They resemble small shrimp and are about a half an inch long and “hop” by using their tails and last three sets of legs.

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What are the tiny colorful clams you find under the sand when digging?

July 23, 2008 by 8 Comments

These tiny colorful clams are commonly known as coquina clams.

Did you see them wriggle under the sand? They use a muscled foot to dig a burrow and hide from their enemies: crabs, sea stars, and snails. They can feed themselves with the muscle coming out of the other end, called a siphon. The siphon basically just sucks in the “vitamins” of the sea for the clam to grow on.

Clams grow very fast in the summer and fairly slow in the winter. You can tell the age of a clam by counting the darker rings. The softer rings are the slow growth of winter. Think how your hair grows longer and faster in the summer.

Did you know that colorful coquina clams are the sign of a healthy beach? Check the video posted here!

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