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Do sharks have bones?

January 2, 2009 by 6 Comments

No sharks do not have bones.

Sharks do have skeletons, but they’re made of cartilage rather than bone. Cartilage is the flexible stuff in the tip of your nose. A cartilage skeleton has its advantages. It’s light, flexible, and it heals faster than bone. In some spots though, sharks need a little extra strength. Their skulls, jaws, and spine are fortified with calcium salts, making them much thicker and stronger. Can you think of why a shark would need strong jaws, skulls, and spines?

by Jim Wharton
Vice President, Education Division, Director, Center for School and Public Programs, Mote Marine Laboratory

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Are stingrays related to sharks?

January 2, 2009 by 7 Comments
English: Various types shown. Taken at Mote Ma...

Image via Wikipedia

Stingrays and sharks are very closely related. They belong to a group of fishes called the elasmobranchs. All elasmobranchs have 1) skeletons made of cartilage (the flexible material that makes up the tip of our nose and ears) and 2) 5-7 gill slits. Elasmobrachs includes sharks, rays, and skates.

It’s not entirely incorrect to think of stingrays as flattened sharks. On the inside, they’re just about the same. There are some animals that blur the lines between the two. Angel sharks and wobbegongs are flat, but they’re not rays. Then there are sawfish (which are rays) and sawsharks (which are sharks). Sharkrays are just plain confused. As a general rule, if the gill slits are on the bottom, it’s a ray. If they’re on the side, it’s a shark.

Jim Wharton
Vice President, Education Division, Director, Center for School and Public Programs, Mote Marine Laboratory

Do you have another great question? Email info@beachchairscientist.com!

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How do fish float?

November 21, 2008 by 1 Comment

wikifishblutangThere are a few different answers – depending on what type of fish we are asking about.

The most sophisticated types of fishes – bony fishes – have a swim bladder. These fish can inflate their swim bladder with gas from a special gas gland. The gas is basically oxygen from the fish’s blood. Bony fishes that spend most of their lives on the bottom of the ocean floor (e.g., flounder) don’t have a strong swim bladder – therefore, don’t float.

Sharks, skates, and rays are all types of fish. However, these fishes are more primitive – lacking bones. They stay afloat with a liver filled with oil. They use long pectoral fins for balance in mid-waters while maintaining a light framework. The ‘light framework’ is made up of cartilage (the same material found in our nose and ears).

Image (c) wiki-fish.com. (Yellow Tang – a true bony fish)

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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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