What is a sea sponge?
Is it a plan or is it an animal?
Sea sponges are not plants. They are relatively basic multi-celled animals without a brain or a central nervous system. They also do not have tissues or organs like other animals do, rather, they have specialized cells to perform necessary functions. Some of these cells are in charge of digestion, some of reproduction and others for bringing in and filtering water so that the sponge can feed.
Sponges are classified as invertebrates, which means they do not have backbones, and they make up an entire phylum of animals (Phylum porifera). They come in many different colors, sizes, and shapes and, since very few animals eat them, they can live for a very long time. Some types have been found to live over 200 years.
Their skeleton is formed from spicules made of silica (a glass-like material), calcium or calcium carbonate materials, and spongin, a protein that supports the spicules. Their body texture looks very much like the texture of your kitchen sponge. It is full of pores whose job is to filter lots and lots of water.
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Facts and things to keep:
Where do sea sponges live?
Do they move around or stay still?
Well, they are called sea sponges because in oceans and the seas. They can be found in all of the oceans and can live in both warm and cold water as well as both in deep and shallow water.
Although there are few exceptions to this rule, they are mainly saltwater creatures. That means that the overwhelming majority of the species would quickly die if you put them in fresh water. They are also very sensitive to air and they can’t survive for long out of the water.
They like to inhabit areas where the water is clear and clean. This is because they filter water through their pores and if that water was muddy and dirty their pores would be filled with that dirt and they would die.
Sea sponges are sessile creatures, they don’t move. Instead, they stay put in one place attached to the sea bed (or to lake or river bed for those few exceptions). Their immobility is what mainly drives the misconception in many people of sponges being plants.
The habitat of sea sponges:
Wanna see sponges in their natural habitat? Then watch this short and beautiful 3-minute trailer about them.
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Where do sea sponges live?
Do they move around or stay still?
Well, they are called sea sponges because in oceans and the seas. They can be found in all of the oceans and can live in both warm and cold water as well as both in deep and shallow water.
Although there are few exceptions to this rule, they are mainly saltwater creatures. That means that the overwhelming majority of the species would quickly die if you put them in fresh water. They are also very sensitive to air and they can’t survive for long out of the water.
They like to inhabit areas where the water is clear and clean. This is because they filter water through their pores and if that water was muddy and dirty their pores would be filled with that dirt and they would die.
Sea sponges are sessile creatures, they don’t move. Instead, they stay put in one place attached to the sea bed (or to lake or river bed for those few exceptions). Their immobility is what mainly drives the misconception in many people of sponges being plants.
What do sea sponges eat?
How do you even feed yourself without a mouth?
Sea sponges don’t have a mouth and they lack distinct digestive, circulatory, excretory and respiratory systems. The water that flows through their pores helps them support all these functions. Therefore, they feed by filtering small organisms and organic debris particles that come in with the water.
As water filters through a sponge’s porous exterior, the sponge receives the necessary food and oxygen, and dispels waste. Inside the sponge, the channels are lined with tiny hair like structures called flagella. The flagella create currents to filter bacteria out of the sponge’s cells and trap food within them.
Sponges are not particularly picky with their food. They feed on whatever the ocean currents may carry inside them and they have the ability to digest tiny organisms and large particles. The sponges that grow on the coral reefs, or near them, have access to plenty of particles rich in nutrients. On the other hand, those living in waters with an inadequate supply of food may become carnivorous, using sticky threads or hooked spicules to capture prey like crustaceans and other small animals.
Also, they rarely become the food. This is because they often use chemicals (toxins) to deter predators like fish and turtle from eating them.
About food, poop and being the food:
Wanna know more about the feeding of sea sponges? Then watch these short and informative videos about it.
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How do sea sponges reproduce?
How can you have babies when you’re not able to move?
Sea sponges reproduce by both sexual and asexual means.
Sexual reproduction:
Most sponges that reproduce by sexual means are hermaphroditic and produce eggs and sperm at different times, alternating between sexual roles (each adult sponge can act as either the female or the male in reproduction).
Sperm is released into the water by the sponge that plays the male role and is dispersed by water currents. At some point it finds its way inside sponges that play the female role, and fertilization of eggs occurs internally. Eventually, larvae are released from the female sponge and float around as plankton for a while, until they find a suitable place for attachment.
Asexual reproduction:
Asexual reproduction means that there is no fusion of male and female cells. It is a method of genetic cloning. Sponges that reproduce asexually do so by producing buds, which in essence are packets of several cells of various types inside a protective covering. Some of these buds break off from the main body, drift away and begin to grow again as new sponges on suitable substrate.
Sea sponges and their strange sex:
Wanna know more about sea sponge reproduction? Then watch this very informative 4-minute video lecture about it.
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Wanna see sponges having their strange sex? Then watch this beautiful 4-minute marine footage with sponges going at it.
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How do sea sponges reproduce?
How can you have babies when you’re not able to move?
Sea sponges reproduce by both sexual and asexual means.
Sexual reproduction:
Most sponges that reproduce by sexual means are hermaphroditic and produce eggs and sperm at different times, alternating between sexual roles (each adult sponge can act as either the female or the male in reproduction).
Sperm is released into the water by the sponge that plays the male role and is dispersed by water currents. At some point it finds its way inside sponges that play the female role, and fertilization of eggs occurs internally. Eventually, larvae are released from the female sponge and float around as plankton for a while, until they find a suitable place for attachment.
Asexual reproduction:
Asexual reproduction means that there is no fusion of male and female cells. It is a method of genetic cloning. Sponges that reproduce asexually do so by producing buds, which in essence are packets of several cells of various types inside a protective covering. Some of these buds break off from the main body, drift away and begin to grow again as new sponges on suitable substrate.
Sea sponges and their role in the ecosystem:
What is their place in the marine environment?
One remarkable feature is the filtration capacity of sponges. Sponges are master filters and, depending on the particular species, may filter from 1.000 to 20.000 liters per kilogram of tissue each day. That’s a lot of water. And this is why scientists believe they can be important factors to changes in water quality, whether good or bad.
Sea sponges are important in nutrient cycles in coral reef systems. They can remove up to 95% of bacteria and particles from the water and 90% of dissolved organic carbon, thereby converting suspended particles and dissolved matter into food for other animals. Also, through the structural complexity that they add to their environment, they provide refuge, spawning areas for fish and specialized habitats for other animals.
Furthermore, sponges seem to play a role in the recirculation of carbon, phosphorous and nitrogen, thus preventing harmful ecosystem changes and helping other organisms in the area survive.
Sponges are also important in science and medicine, but this is a discussion for another topic (see below).
Did you know that the sea sponge could be the first animal on Earth? Watch this very informative 2-minute video which is all about it.
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Facts and things to keep:
The role of sea sponges in science:
What is their importance in pharmaceuticals & biotech?
Many sponge species contain toxic substances, probably in order to deter predators. Some of these chemicals have been found to have beneficial pharmaceutical effects for humans, including compounds with respiratory, cardiovascular, gastrointestinal, anti-inflammatory, antitumor, and antibiotic activities.
Sea sponges and their associated microorganisms have also been identified as having significant biotechnological potential. They are the single richest and most bountiful source of marine natural products for human health applications (i.e. pharmaceuticals). Thousands of ‘sponge ground’ compounds have been discovered to date, with many showing potent bioactivity and some possessing useful anti-fouling and anti-cancer properties. Perhaps, the most interesting potential application is the use of their intricate silica-based skeletons in novel approaches to tissue engineering and regenerative medicine.
More than 5,300 different natural products are identified from sponges, and more than 200 additional new metabolites from sponges are reported each year. Sponges have the potential to provide future drugs against important diseases, such as cancer, a range of viral diseases, malaria, and inflammations.
Did you know that sea sponges could be key in the fight against Tuberculosis? Watch this very informative 3-minute video and see Dr Diana Quan – a researcher at the Centenary Institute – talk about her fight against the world’s top infectious disease killer, TB.
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Wanna see scientists absorbed by deep-sea sponges? Then watch this interesting 4-minute video all about it.
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The role of sea sponges in science:
What is their importance in pharmaceuticals & biotech?
Many sponge species contain toxic substances, probably in order to deter predators. Some of these chemicals have been found to have beneficial pharmaceutical effects for humans, including compounds with respiratory, cardiovascular, gastrointestinal, anti-inflammatory, antitumor, and antibiotic activities.
Sea sponges and their associated microorganisms have also been identified as having significant biotechnological potential. They are the single richest and most bountiful source of marine natural products for human health applications (i.e. pharmaceuticals). Thousands of ‘sponge ground’ compounds have been discovered to date, with many showing potent bioactivity and some possessing useful anti-fouling and anti-cancer properties. Perhaps, the most interesting potential application is the use of their intricate silica-based skeletons in novel approaches to tissue engineering and regenerative medicine.
More than 5,300 different natural products are identified from sponges, and more than 200 additional new metabolites from sponges are reported each year. Sponges have the potential to provide future drugs against important diseases, such as cancer, a range of viral diseases, malaria, and inflammations.
Sponge diving & harvesting:
How far back in time does it go?
A little bit of history:
Sponge diving is the oldest known form of the art of underwater diving. Its goal is the retrieval natural sea sponges for general human use.
Most sponge that we use today are synthetic, but in the old days sponge was collected from the sea floor. Some of the finest-quality sea sponge, this ancient marine creature with a body full of pores, has always been found in the Aegean and the warm waters of southeastern Mediterranean.
It is unknown when exactly the sponge became an article of use. In ancient Greek texts, Homer and Plato mention the sponge as an object used for bathing. The ancient Greeks knew about sea sponges and their usefulness for scrubbing and cleaning purposes, and for maintaining personal hygiene. Sea sponge was also used for padding helmets and for filtering water.
Later through trading, other Europeans – like the Romans – started to use soft sea sponges for many purposes including making padding for helmets, portable drinking utensils and to filter and purify municipal water reserves. Until the invention of synthetic sponges, they were used as cleaning tools, applicators for paints and ceramic glazes, and discreet contraceptives. However, by the mid-20th century, over-fishing and climate changes had brought both the populations of sponge and the industry built around it close to extinction.
Are all species of sponge harvested?
Nope. Most sponges are too rough for general use due to their structural spicules composed of calcium carbonate or silica. But two genera, Hippospongia and Spongia, have soft, entirely fibrous skeletons. These two genera are most commonly used by humans.
Are sea sponges endangered today?
No, sponges are not on the endangered species list. However, there are threats to their habitat in some areas due to factors such as pollution, disease, exploitation, or hurricanes.
Wanna know more about diving and harvesting sponges? Then watch this very informative 5-minute video about the sponge divers of Greece.
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Stuff about the sea sponge industry:
Sponge farming & aquaculture:
Can we farm sea sponges?
Yes we can.
Sea sponge aquaculture is the process of sponge farming under controlled conditions. Aquaculture is nothing new. It’s conducted for centuries in the world’s oceans with various techniques and methods (such as such the rope and mesh bag method – see video).
The growth rate of sponges is influenced by factors such as light, salinity, pH, dissolved oxygen and the accumulation of waste products. In sponge farms, sea sponges can be produced on a commercial scale to be used as bath & shower sponges, or to extract bioactive compounds which are found in certain sponge species.
The advantages of sea sponge aquaculture are the minimum infrastructure required to establish a sponge farm, the fact that there no negative effects on the natural sponge or coral populations and the potential to be used as a source of income for populations living in developing countries.
Interested in a video about sponge farming? Then watch this super cool 9-minute video with some amazing footage.
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Sponge farming & aquaculture:
Can we farm sea sponges?
Yes we can.
Sea sponge aquaculture is the process of sponge farming under controlled conditions. Aquaculture is nothing new. It’s conducted for centuries in the world’s oceans with various techniques and methods (such as such the rope and mesh bag method – see video).
The growth rate of sponges is influenced by factors such as light, salinity, pH, dissolved oxygen and the accumulation of waste products. In sponge farms, sea sponges can be produced on a commercial scale to be used as bath & shower sponges, or to extract bioactive compounds which are found in certain sponge species.
The advantages of sea sponge aquaculture are the minimum infrastructure required to establish a sponge farm, the fact that there no negative effects on the natural sponge or coral populations and the potential to be used as a source of income for populations living in developing countries.
The processing of sea sponges:
Can a sea sponge be used right off the boat?
No. A sea sponge cannot directly be sold or used as commercial product. It has to be made into one before it’s used. That means that there has to be some processing between its harvest and use.
Actually, the process starts on the boat right after the harvest. The sponges are deposited on the deck and even covered with wet cloth. The outer tissue starts to break down and fall apart. Every now and then the sponges are thrown into the sea to be washed and then squeezed to remove their outer tissue and other foreign bodies (sand, rock, debris, crustaceans etc). Then, they are laid in the sun again. This in and out water will be repeated many times over several days until all – or most – unwanted stuff is removed and the skeleton of the sponge is all that remains.
When the sponges are deemed to be as thoroughly cleaned as possible, they will be hung from ropes to dry and, then, sent to a sponge processing warehouse. There, they will be soaked again and dried to the point that they that they are still wet but without any excess water inside them. After that they will be cut and clipped by hand and arranged into various types, sizes and qualities. But we’ re not done yet.
The sponges will be soaked again into a dilute solution of chlorine that helps dissolve any remaining bits of root, sand or any other debris that may have have escaped the previous cleaning process. The sponges are then washed in a sodium solution in order to remove the chlorine and any remaining particles form the sponge. It’s exactly at this stage of the process that the sponges acquire their lighter brown or yellow color.
Wanna see a short demonstration of the final stages of the cleaning and bleaching process? If yes, watch this very interesting 2-minute video.
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What does a sea sponge look like? Most sea sponges are of dark color when harvested. It is only after the processing that they acquire their familiar lighter brown or yellowish color.
Sea sponges of commercial value:
Are all the species of sponge useful to humans?
Out of the more than 8.000 species of sea sponge that are known today, and excluding the species that are of interest to marine biologists for biotechnology purposes, you’ll hardly find more than 15 species in the market today to be used as bath sponges or for any other cleaning or scrubbing application.
The main one of these are the following:
Sea sponges of commercial value:
Are all the species of sponge useful to humans?
Out of the more than 8.000 species of sea sponge that are known today, and excluding the species that are of interest to marine biologists for biotechnology purposes, you’ll hardly find more than 15 species in the market today to be used as bath sponges or for any other cleaning or scrubbing application.
The main one of these are the following:
Commercial uses of sea sponges:
What are sea sponges used for?
The sea sponge have been used for millennia by many cultures all over the world for all kinds of different purposes, ranging from general cleaning to filtering, padding or artistic applications. Today, people use sea sponges mostly for the following purposes:
Personal Hygiene
Sea sponges are routinely used as natural bath sponges, which is by far their most common commercial use today. Sea sponges are very soft to the skin and ideal for cleaning the body and the face. They are an excellent tool for a thorough skin exfoliation and deep pore cleansing.
Moreover, sea sponges possess antibacterial and hypoallergenic properties and are toxin-free, which makes them safe even for people with very sensitive skin and perfect for baby and infant care.
Some people prefer to use them because of their ability to absorb a lot of water and soap and not drip which, along with their velvety sense, can turn an everyday bath into a luxurious experience.
Cosmetics application and removal:
Sea sponges are used for applying and removing cosmetics, such as makeup, lotions etc. They are especially useful for cleansing the pores of the skin and for removing residues and other impurities. Also, they are excellent for moisturizing the skin before shaving.
General cleaning purposes:
Sea sponges are some of the most versatile cleaning tools you’ll find out there for general cleaning purposes. When wet they are softer than artificial sponges, which makes them much less likely to damage surfaces and finishes. People use them to wash walls and other surfaces, vehicles such as cars, boats and aircrafts, or for hand washing dish, crystal, china or silver.
Ceramic art:
Sponges are used in pottery by ceramic artists for various purposes such as controlling the amount of water in the clay, smoothing out rough edges and finishing lathe machine. However, the advantage of using sea sponges over synthetic ones is that you get more textural variety. If, you are an artist yourself you should have a few in your studio.

Credit: Shutterstock / Wavebreakmedia
Pet cleaning & care:
Naturally, sea sponges are used for pet care. If something feels good and enjoyable to you, why would it be any different for your pet, right? So people use them to wash their dogs, cats and horses.
Wall painting & home decorating:
Sea sponges are used for coloring walls, ceilings, surfaces and furniture. They do not substitute brushes or other traditional tools, but they can you obtain interesting shades, spotted effects or various other imprints. If you like decorating you should really try them.
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Painting & drawing:
For painting and faux finishing, sea sponges can help you create an unlimited effects, marks, and gestures. With simple and easy to learn techniques you can give your painting texture, nuance and complexity.
If drawing is your thing, sea sponges are excellent for these smudging effects and for blending chalk pastels and charcoal.
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Sea sponge tampons:
Also known as menstrual sea sponges or period sponges. Women use them as a more natural alternative to conventional tampons to help absorb menstrual flow. Sea sponge tampons are very absorbent, comfortable, non-irritating, environmentally friendly. Last but not least, they are a more economic solution since they are reusable.
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