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What is the biggest fish in the sea?

November 18, 2008 by 6 Comments
Picture taken at Georgia Aquarium, pictured is...

Image via Wikipedia

The whale shark is the biggest fish on the planet. The largest whale shark measures about 66 feet long and 74,957 pounds.

Not to be confused with the blue whale, a mammal, which is the largest animal on the planet. The largest blue whale measured about 110 feet and up to 400,000 pounds!

The whale shark got its name because the shark’s mouth is shaped just like baleen whales. Baleen whales and whale sharks both munch on krill. For being the largest fish in the sea the whale shark is surprisingly affable to divers and known as a relaxed fish.

How are ‘whale sharks’ and ‘whales’ different?

Whales are mammals, just like people, and must breathe air. Dolphins, seals, porpoises, otters (and some people say, polar bears) are mammals that live in the ocean (ie., marine mammals). Consult the aquarium guide for more details.

Another difference is that mammals raise their young. Whale sharks give live birth like mammals, but, move on right after and don’t raise them. Most other fish do lay eggs.

Fish also have gills to breathe underwater, unlike mammals that must come up to the surface of the ocean and breathe air.

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Filed Under: Fish, Marine Mammals Tagged With: , , , , ,

How do sea stars eat?

November 18, 2008 by 4 Comments

StarfishFirst, sea stars grip their prey (e.g., bivalves, such as clams and oysters) with their suction feet and pry them apart to eat the muscle inside the shells. Then, once the bivalve’s shell is open, the stomach of the sea star emerges from the middle of the underside of its star-shaped body to absorb the delicious entrée inside itself. After this happens, the animal is full and not going anywhere soon (e.g., me after Thanksgiving dinner).

A sea star is another common name for starfish. Scientists, and the likes of me, are on a campaign to get people to refer to this echinoderm as the ‘sea star’ instead of a starfish. Since, well, they simply are not fish. Similarly, jellies are not called jellyfish anymore.

Check out this video from the Monterey Bay Aquarium of a sea star chowing down!

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Filed Under: Echinoderms Tagged With: , , , ,

What are those yellow looking things that look like a floppy spinal cord?

November 14, 2008 by 2 Comments

The strand of half dollar sized pods is an egg case. Actually each pod has about twenty tiny animals in each pod.knobbed_whelk_with_egg_-case_100_2886

The tiny animal that will grow from this egg case is the knobbed whelk. This is basically a northeast version of a conch (pronounced conk). If you hold the tiny discs up to the sunlight you can see the tiny versions of the whelk developing.

The whelk is a mollusk (like clams and oysters) but only has one shell. This shell grows with the whelk as it gets older – as opposed to the hermit crab which moves out as it gets bigger.

Also, if you hold the whelk shell up to your ear you can hear the ocean. Lastly, do not hold up a whelk shell to your ear if it has a tough protective “door” covering its opening. That’s the mantle and means that an animal inhabits the shell. Please place it right back where you found it.

Image (c) Jo O’Keefe.

 

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Filed Under: Egg Cases, Mollusks, Univalves

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.

Filed Under: Bivalves, Mollusks Tagged With: , , , , , ,

Are flounder born flat?

November 11, 2008 by Leave a Comment

They hatch from the egg looking exactly like typical fish, swimming in the upper waters. After two weeks the bridge of the fish’s nose fades away and then one of the eyes, depending on the species, shifts to one side. The process of becoming a complete “flat” fish takes a bit of time, but, once complete the flounder is content to live the rest of its life on its side on the bottom of the ocean floor.

Winter flounder move their left eye to the right side. Summer flounder move their right eye to the left side. There are many more flounder species, but, this is just an example of where their eyes shift.

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Filed Under: Bony Fishes

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

Filed Under: Bivalves Tagged With: , , , ,

What are those tiny black pods with tendrils near the ends?

October 24, 2008 by 5 Comments

They are egg cases from a juvenile thorny skate. skateThe skate is related to sharks and rays. Sharks, skates, and rays all have a skeleton made up of cartilage, the flexible material that is found in our noses and ears. One tiny skate will hatch from each egg after nine months – hatching under the surface of the water. Usually, what we see wrapped up in the seaweed “wrack line” is the discarded egg cases. Another nickname for these egg cases is the “mermaid’s purse.” Check out this BCS post to learn the difference between skates and rays.

Image (c) NOAA – Alaska Fisheries Science Center.

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Filed Under: Egg Cases, Skates and Rays Tagged With: , , , , , ,

Can you tell how old a fish is by looking at it?

October 20, 2008 by Leave a Comment

fishscaleagerings1There is one possible way to tell how old a fish is while it’s still alive. And, at that, – it’s pretty invasive. You need to take some of its scales (see image).

The scales are similar to the rings of a tree. Depending on how many dark rings you may see (if you were to hold the scale up to a light source) it will determine the age of the fish. However, since scales can regenerate often, the rings could be cloudy and difficult to decipher.  You can get a more accurate age of a fish by other methods which require the fish to be dead. These include reading the rings on the cross-section of a fish ear bone (otolith) or fin ray.

Knowing the age of a fish is very important for understanding how to maintain populations and stocks for fisheries management.

Image (c) eralabs.com.

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Filed Under: Bony Fishes Tagged With: , ,

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: ,