- Some species of sponges are presumed to be alive for more than 15,000 years, meaning they are the oldest marine animals in the world.
- Marine biologists are able to determine the age of a sponge by looking at its size and average growth rate.
- Sponges are heterotrophic, multicellular, produce sperm cells, and they lack cell walls, which is enough for them to be considered animals.
The ocean hides many secrets, and we keep discovering new ones. The creatures living in the deep sea are wondrous, while some could be described as outright scary. Answering the question of which marine animal is the oldest is not the simplest task. There are multiple ways to approach this, and the answer we give you today might change in the future once biologists make a new discovery.
If you are wondering what marine creature species has been living on the planet the longest, the answer is most likely the crusty nautilus. According to experts, this species has existed on our planet for over 500 million years. However, we will talk about a different thing here, and that is the marine animal that can live the longest. The answer may surprise you, but the oldest living marine animal is the Antarctic sponge.
Sponges Are Animals?
Yes, people often forget this, but it is a fact. Sponges living in the sea are indeed animals. They are heterotrophic, multicellular, produce sperm cells, and they lack cell walls. However, they are different from most animals in that they do not possess organs and true tissues. Still, this was enough for science to declare them animals, and who are we to argue?
Not only are sponges animals, but they can also live extremely long. The estimates of how long exactly they can live, but most agree that it is in the range of 10 thousand years. For example, according to a study, one sponge from the species Monorhaphis chuni lived for 11,000 years. But that is not all, we are talking about the oldest marine animal here, and that is the Antarctic sponge. The exact name of the species is Anoxycalyx joubini, and they can supposedly live up to 15,000 years. We say supposedly because it is extremely hard to test this, but all signs point to it being a fact.
The Physical Properties Of Sponges
These sponges are shaped like a barrel and the color of snow. Their age was calculated taking into account their size and their average growth rate. It is interesting to think about all of the things a member of this species has lived through. While it was just a young sponge, wooly mammoths were still stomping all over our planet. These creatures are convincingly one of the oldest organisms on Earth. Even if we halved their approximated age, they would still be the oldest living marine animals.
The body of a sponge is hollow, and what helps it keep its shape is a special substance called mesohyl. This substance has physical properties similar to jelly and is made up primarily of collagen. An extremely dense chain of fibers keeps the mesohyl in place and reinforces it. All sponge species have special channels that lead to the interior of their bodies, and those channels are called ostia.
Ostia is used to digest food. The mesohyl is covered by pinacocytes from the outside, special cells that are used to digest food that is too large to go through the ostia. There are multiple other cells inside the mesohyl, and just by reading this simple description of their physical properties, you can easily see why sponges are considered animals.