Sea Sponges: Characteristics, reproduction, uses and more…..

The Sea sponges are invertebrate marine animals that can live in fresh and salty waters. These striking creatures bear characteristics that really worth to learn about.

They belong to the phylum Porifera which means «pore bearers»and bear  features that until 1825 were not recognized as characteristics of the animal kingdom. They are very primitive living beings that inhabit mostly in shallow waters, although there are also species of deep habitats (up to 5000 meters) and some, very few, are freshwater. Let’s learn now about…

Main Characteristics Of The Sea Sponges

The sea Sponges are relatively simple multicellular animals which lack tissues or organs but have specialized cells to perform their vital functions. Each of these cells has a job: some are in charge of digestion, others reproduce, others carry water and the sponge can filter the food, and others are used to get rid of the waste. Their bodies consist mainly of a gelatinous mass interspersed between two main layers of cells.

One of their most outstanding traits lies in the porous structure of their bodies, from which they have received the name Porifera. When examined closely, small and numerous pores can be seen as well as  otherslarger but  scarcer. The water flow from which they feed  penetrates through the first ones, (inhaling pores or ostioles), with organic matter in suspension .

Through the seconds ones, ( osculum), the water comes out. Due to such characteristics sea sponges must inhabit the water, either sweet or salty and must be fixed to a solid substrate. However, it has been discovered that some species are able to attach themselves to softer substrates such as sand or mud.

Sea Sponges: Common Anatomy

The Anatomy of the Sea Sponges.

The sea sponges´ body can adopt different shapes according to the climatic conditions where they live.  There are tubular, globular, lobular or cup-shaped sponges, even flattened and with long shapes, that resemble more a carpet than an animal. On the other hand, they also have very varied and intense colors that are largely along with the coral reefs  responsible for the great beauty of the sea.

Let´s learn about their body parts


This is the outermost layer of the sea sponges and has broad and long pseudo epithelial cells called pinacocytes. The Pinachoderm is crossed by dermal pores which in turn are covered by a coiled cell (porocyte), which is responsible for attracting water.

Some species of sea sponges also have a cuticle (layer of collagen) which covers and sometimes replace the pinachoderm.


The inner of the sea sponge body is covered by a series of flagellated cells that collectively are called coanoderms. These flagellated cells are individually called choanocytes and are responsible for producing the flow of water, According to the species of the sea sponge, the coanoderm can be as thick as a cell phone or it can be retracted or subdivided into clusters of chambers where independent choanocytes are located.


This area is located between the pinachoderm and the coanoderm. The mesohile contains support fibers, spicules of the skeleton and amoeboid cells that have a huge importance in processes such as digestion, the secretion of the skeleton and the transport of nutrients and waste.


The sea sponges don´t have a skeleton as most animals have.  Theirs is made up of many elastic fibers of collagen, which comprise their protean structure and may be combined with siliceous spicules which are based on hydrated silicon dioxide, or calcareous spicules formed on the basis of calcium carbonate.

Let´s meet them 

The Sea Sponges´Cells

One of the most outstanding features of the sea sponges is that most of their cells are totipotent, that is, they can transform into any of the other cell types according to their needs. Therefore, it is considered that the sponges have a tissue cellular organization and lack true embryonic layers. This unique property makes them able to regenerate even in cases of having lost large pieces.

Types of cells

Pinacocytes: The pinacocytes make up the external coating of most sponges. The have protective and  phagocytosic functions. (They surround solid particles with their cytoplasmic membrane and introduce them into the cell.)

Porocytes: They are cylindrical cells of the pinacoderm with an adjustable central channel that allows more or less volume of water to pass inwards. They are exclusive of calcareous sponges.

Coanocytes: These are the most curious cells that the sea sponges have. They are made up by a long central flagellum that in turn is surrounded by a crown or collar of microvilli that are connected to each other thanks to mucous filaments. These flagella are responsible for creating water currents loaded with bacteria, phytoplankton and organic matter that will be trapped in the microvilli to be subsequently ingested.

Spongeocytes: They are found in the mesohile and are responsible of segregating thick collagen fibers that are called sponginous fibers. They are the main support of the sea sponge.

Sclerocytes: These cells produce spicules (calcareous or siliceous), but tend to disintegrate once the spicule secretion process is completed.

Amyctoids: They are also found in the mesohile and are capable of transforming into another type of cells. They are really important in the digestive processes because they accept particles that have been ingested by the choanocytes, being also responsible for transporting the excretions. Moreover, they play a fundamental role in asexual reproduction.

Spherulous cells: They are responsible of excreting wastesince  They accumulate granules that are later released to the exhaling current.

Let´s learn about totipotent cells

How Do Sea Sponges Feed On

Their feeding behavior responds to their anatomical structure, which is quite simple. It consists of a sac-shaped cell mass through which the water circulates, carrying the oxygen that allows them to breathe and the nutrients with which they subsist. Since sponges don´t have real tissues or organs (therefore, they don´t   have a digestive system, like that of more complex living beings), their only means of survival relies in their cells. Thus, sponges don´t have an active feeding, since they are sessile animals, that is, they are attached to the substrate where they live, like the seabed.

Carnivorous Sponges

A few species that live in waters where the supply of food particles is very poor, feed on crustaceans and other small animals. So far only 137 species have been discovered and most belong to the Cladorhizidae family.   Little is known about how these sponges capture their preys although it is believed that some species use a kind of sticky threads. Most carnivorous sponges live in deep water up to 8,840 m deep which the main reason of such feeding habits and the lackness of information about them.

Simbiotic Relationships

Some sponges have organisms inside their bodies called photosynthetic symbionts (Organisms that usually live in the body space of another, without harming it), which are very useful for their survival. They can also host bacteria. This relationship is very common in the case of freshwater sponges that often develop symbiotic relationships with green algae to benefit from the nutrients produced by them. In the case of marine species they usually host other organisms capable of carrying out the photosynthesis, such as cyanobacteria, and in some cases dinoflagellates, from which they obtain between 48% to 80% of their energy requirements.


The reproduction of the sea sponges can be asexual or sexual.

Asexual reproduction

This type of reproduction is the result of the body´s fragmentation, which occurs due to exposure to unfavorable environmental conditions or as a part of the normal life cycle. The most frequent type of asexual reproduction is by budding.  In the body of an adult sponge appear lateral buds that grow and differentiate into young sponges, which separate for any or other reason, to live independently or make up a new individual of the colony. Like all animals that reproduce asexually, sponges have a huge power of regeneration and reconstitution.

Sexual Reproduction

Sponges are hermaphrodites, since every specimen has ovules and sperm which go out from the sponge dragged by the water´s current. Then they reach the inhaling conduits systems of other nearby sponges and penetrate into their body being caught by the choanocytes, where the fertilization takes place. In some species, the sperm don´t go outside but fertilize the inside of the same individual.

Let´s learn

Sea Sponges Classification

The Phylum Porifera is divided into three kinds of sponges: Calcarea class, Hexactinellida class and Demospongiae class. We will describe each class in detail below:

Class Calcarea

These sponges have needle-shaped spicules or with three or four rays, made up calcium carbonate. The species belonging to this class are small and rarely exceed 10 centimeters. They usually inhabit shallow waters, although there is evidence that they can inhabit abyssal areas at depths of even 6000 meters. The species from this class are marine and present the three types of channel systems: asconoid, sycoid and leucnoid.

Hexactinellida class

The sponges belonging to this group are called vitreous sponges, since their spicules are usually grouped to form a network.  Moreover, they are made up of silicon and have six radii (triaxonic). All species of this class are marine and inhabit deep water (mainly in  Antarctica). Their flagellated chambers are of syconoid and leuconoid type. Arounf 500 species are known, among them Hexactinella, Farrea, Euplectella and Aphrocallistes,


These sponges  have siliceous spicules (no triaxonic), sponging or both. The famous «bath» sponges belong to this family. Most live in marine environments, although a family that lives in freshwater environments, such as Spongilia lacustris and Ephidatia fluviatilis, has been reported. They are of the leuconoid type.

In addition to bath sponges, other relevant genera belonging to this class can be mentioned, such as: Thenea, Cliona, Myenia, Poterion and Callyspongia. The Poecilosclerida, characterized by its peculiar habit of carnivorous feeding belong to this class.

Homoscleromorpha class

This is the smallest class of all, since it´s made up by only 87 species belonging to the following genera: Oscarella, Pseudocorticium, Corticium, Placinolopha, Plakina, Plakinastrella and Plakortis. They are characterized by flagellated pinacocytes, Their skeleton is variable, they may or may not have silica spicules, and they have a basement membrane.

When the skeleton is present, it consists of tetraxonic silicon spicules with four rays. Most species have cushion shapes and vary widely in their coloration, exhibiting blue, purple, green, yellow, red tones, among others. They inhabit dark or semi-dark ecosystems and can be located both in shallow water and at depths greater than 100 meters.


Habitat and Distribution.

Since sea sponges can adapt to different climatic conditions, facing situations that for other animals would be impossible to tolerate, coping with water pollution better than anyone and having very few predators, they are found in practically all the seas and oceans of the world.

In addition, due to their high filtration skills (a sponge 10 centimeters high and 1 centimeter in diameter can filter up to 22.5 liters of water per day) sea ​​sponges are the dominant animals in many of the marine benthic habitats, tolerating remarkably the waters polluted by hydrocarbons, heavy metals and detergents. They are able to accumulate these pollutants in large quantities without this representing a significant damage to them.


The sea sponges lack of sensory organs that help them to notice the presence of enemies, but that´s not a big problem for them. They have very few predators, thanks to their spicule skeleton and its high toxicity. Moreover, many of them have sharp barbs capable of perforating soft tissues, in addition to producing stinging substances. Their main enemies are the polychaete worms, some crabs , starfish , opisthobranch mollusks, echinoderms and fish, but generally they are very specific species and mostly predate on a specific species of sea sponge.

These interesting and weird creatures have many toxins and antibiotics such as the polytheonamides that they use to avoid predators, which are being investigated by scientists for their usefulness in the pharmacological area, since they have anti-inflammatory, cardiovascular, gastrointestinal, antiviral and antitumor properties.

Common Uses of the Sea Sponges

The Sea sponges´ fishing has been a highly exploited market. It is known that they have been used since very remote times, with the Greeks being the first to discover their benefits.  They were fished in the Hellenic archipelago and used for personal hygiene and even to cushion the warrior’s helmets as well as their heavy armor. Nowadays they are also used for cosmetic purposes, such as makeup application, to paint and for ornamental purposes. Let´s learn

Personal hygiene

Their best known use is in personal hygiene since they are very soft which make them ideal for grooming babies during the first months of their life. Even adults and people with sensitive skin appreciate the quality and pleasure they experience when using sea sponges.   Dermatologists recommend natural sea sponges for very sensitive skin and skin with allergies.


Bathroom accessories.

Natural sea sponges have also become an elegant accessory for bathrooms: in hotels, yachts and restaurants it is very common to see exhibits of natural sponges as part of the furniture. They are usually displayed in glass containers with sand and small stones or near sinks and bathtubs, thus simulating marine life and natural well-being.

Ceramic Industry.

They are used for the finishing of the lathe machine, since they don´t stain nor  leave a trace on the piece that must be modeled

Footwear Manufacturers

Marine sponges are used in the footwear manufacturing industry to gently spread the color on top of the footwear and also to polish them.

Painting and Fine Arts.

The sea sponges are also widely used in the restoration of works of art, for the dry cleaning of paintings. Their most common use is for the creation of decorative effects and rollers to extend the color in walls, canvas

Let´s watch and learn


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