What is this?

Question

I was walking along the beach and came upon this. I'm guessing it's an egg sac for something. It is roughly 8"X4"X1"" in size. What "something" did it come from?

Here's the link to the picture of it.

http://img142.imageshack.us/img142/5007/sthisau3.jpg

I don't think it's man made. It was empty. It had a slit on one side.

Answer 1

What a wonderful picture! What you have found is the egg capsule (without the former inhabitant, an embryo) of a skate.

About 75% of all elasmobranchs (sharks, skates and rays) are viviparous, meaning they retain the eggs in the uterus and give birth to living pups. But 25% of all elasmobranch species are oviparous, meaning they lay eggs. While they differ somewhat in shape, they all more or less look like the one you found on the beach.

As one can tell from your picture, the capsule is somewhat interestingly shaped. This has a good number of reasons. For one, there are the horns to either side of the capsule, which help in anchoring the capsule to the substrate on the ocean floor. Mother skates will deposite the eggs in a slight current, which will guarantee good oxidization (oxygen rich water is constantly moved through the chamber of the egg). The leathery consitency of the egg (which on your picture due to dehydration had been lost) offers sufficient protection for the embryo, as well as permits for water to constantly flow. The capsule is actually not closed tight between the horns on the short edges.

The egg case that you found was formed in the female reproductive tract by a structure called the oviducal gland. Basically, the gland secrets the material that forms the shell into the uterus. when you open an oviduct at a time when the egg capsule is formed you will find that the lower half of the capsule is already fully there, with a very large egg sitting in it, while the upper half is still missing and will be formed subsequently. The egg simply "drops" into the capsule, so to speak.

During the embryonic development the animal is entirely dependent on the nutrients stored in a yolk sac, which is why the eggs are so big. The embryo needs to be provided with enough food for a long incubation period, which lasts almost as long as in humans (depending on the species). The yolk sac is connected to the embryo via an umbilical chord-like structure. At the time of hatching however, all that is left is a little "belly button," which over time disappears altogether.

Even in viviparous species, egg capsules are formed, but they are not as hard and thick as in oviparous species. Nonetheless, the embryo is encapsulated for a good part of its intruterine development and eventually hatches from its capsule inside the mother's uterus. What now differentiates the differnt types of reproductive modes in viviparous elasmobranchs is the way nutrients are provided for the embryo. (I recently answered a question on that issue, so if you are interested check it out.) After ten to 24 months (depending on the species), the baby shark is born and ready to go.

Great picture and a fun question. Hope my answer helped.

PS: It is not an egg of a shark. Shark eggs have long, stringy appendages with which the mother attaches the egg to the substrate. It is also neither a plant structure nor a crustacean. As for the "ray" egg, the shape of the egg suggests a Rajiform skate ratyher than a ray. Depending on where you found the egg one could possibly narrow down to genus and possibly species. If you are in the northeast Atlantic seabord I would wager Raja as genus, but wouldn't bet all my money on it...

Answer 2

Mermaid's purse is a nickname for the egg case of a skate, a type of fish similar to the ray. The name comes from the case's appearance, as if it were a bag with handles on each side. Because they float, the cases can often be found washed up on beaches.

Answer 3

it looks man-made to me.

What was inside when you found it?
Was it heavy? Did it float on water?
What does the material feel like? Like some shell? like plastic? like metal?

If I had to guess without anymore information, I'd say it's some sort of buoy with a plastic bag to hold it and attach it to something.

As you can see, some parts look like they have been torn off, and the torn off part look like plastic to me.
Also, if you've found it on the beach and if it's man made, a logical assuption would be that it's used in the sea and pushed on the beach by the tide. That's why i'm thinkin of a buoy: maybe to hold a net next to the surface (fishing)

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yep, looks like i was wrong : it's a RAY EGG
(2 links for other pictures of ray eggs and 1 link for an article on rays)

Answer 4

It is part of a underwater plant, a type of seaweed. I do not know the name of it, but that part is the seed pod of the plant. On the beaches where I go, you rarely see it as a whole plant, it must get torn up into pieces in the water.

Answer 5

it looks some what like an empty egg case for a shark, ive only seen drawings of them, but they look similar, also given the nick name "mermaid's purse"

Answer 6

That's totally a sting ray egg case.

Answer 7

Kelly C is right, it is a shark's egg, good one Kelly! I think to be more precise, it belongs to a ray, which are technically sharks! haha, nice find, you dont see that everyday!

Answer 8

That is a shark egg case. I don't know what type of shark though.

Answer 9

That is a sharks egg!!http://www.bazooka.ne.jp/~kasuga/01doubutu/04fish/Shark-Egg/Shark-Egg.jpg

http://www.cryptio.net/~viv/aquarium/sharkegg.JPG

http://marinelifephoto.com/fish_pg2/pages/CAF-17.htm

http://www.mtkembla-e.schools.nsw.edu.au/gallery/galleryimages/SharkEgg.JPG

Answer 10

Got no idea wow.I would like to know you should have taken it