Marine Invertebrates 101: Sea Sponges

Invertebrates are animals without a backbone yet they account for 95% of all known animal species. Amazing isn’t it?

To introduce you to the wonderful world of marine invertebrates, our Education Team is starting this series of blog posts called Marine Invertebrates 101 to highlight the amazing collection of marine invertebrates in S.E.A. Aquarium. So that on your next visit here, apart from admiring our wide range of fish, you’ll also be able to recognise and better appreciate these marine invertebrates.

Barrel Sponge (Xestospongia testudinariaI) at our Reef Wall Habitat

To start off this series, we have the fascinating sea sponges.

8 things you probably don’t know about sea sponges

1. They’re animals, not plants

Sea sponges are members of the phylum Porifera [paw-rif-er-uh], which means “bearing pores” in Latin.

Contrary to their appearance, sea sponges are not plants but animals. These multi-cellular animals (made up of different cell types) function just as well as any other animal – even without tissues and organs such as brain or heart. What’s more, they are estimated to have existed on this Earth for at least 500 million years!

2. Not just squares

SpongeBob, whose character was inspired by sea sponge, may be square in shape but in reality most sea sponges are irregularly shaped.

Image: nickelodeon/Wild Horizons/UIG via Getty Images/mashable composite. Source: Mashable

3. Needle-like skeleton

There are approximately 5000 known species of sponges, and they can be classified into 3 distinct groups based on the material of their ‘skeleton’: Hexactinellida, Demospongia and Calcerea.

The skeleton of sea sponges comprises of small, needle-like structures called spicules. Sea sponges classed under Hexactinellida have glass spicules, while those classed under Demospongia have either silica spicules or spongin fibres.  Sea sponges classed under Calcerea have spicules made of calcium carbonate.

Different types of spicules. Image source: Pinterest

4. They obtain food and oxygen through filtration

Every day, sea sponges filter large amounts of water, about 20,000 times their own volume, to obtain food (e.g. bacteria, plankton) and oxygen.

Although the majority of sea sponges are filter feeders, a few species (such as the Harp Sponge) are carnivorous and have developed active means to grab food like small shrimps from the water.

Harp Sponge (Chondrocladia lyra). Image Source: Mission Blue

5. Toxic, with few predators

Sea sponges have few predators because they are toxic to many animals except sea turtles.

Orange Phakellia Sponge (Phakellia sp.) at our Reef Wall Habitat.

6. Important in the development of anti-cancer drugs

Sea sponges have huge roles to play in the medical field. They contain chemicals that are useful models for the development of a number of anti-viral and anti-cancer drugs.

7. Used for cosmetic purposes

Before synthetic sponges were invented, sea sponges were (and still are) harvested to be used as bath and cosmetic sponges.

Image Source: Farm to Girl

Before synthetic sponges were invented, sea sponges were (and still are) harvested to be used as bath and cosmetic sponges.

8. They can regrow broken parts

Just like Wolverine, sea sponges have tremendous self-regenerating powers. Even when broken in two, their cells are capable of reconstructing themselves to regrow the broken parts.

Here’s an interesting video to help you learn more about sea sponges:

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