eponge 011. Diversity of shapes and colours
© Thierry Perez
eponge 02 2. Organisation of the sponge
© Pour La Science
eponge 03 3. Sea slug
© Thierry Perez
eponge 04 eponge 05 eponge 06 4,5 et 6. Reproduction in sponges
© Marseille Oceanography Center (4 et 5)
and Thierry Perez (6)
eponge 07 eponge 08 eponge 09 7, 8, 9 and 10. Main species of sponge
© Thierry Perez
eponge 11 eponge 09 eponge 10 11, 12 and 13. Some other species
© Thierry Perez

"All about sponges" by Dr Thierry Perez, researcher at the national centre for scientific research, Marseille

Sponges have been known and used since antiquity.

Toilet sponges only represent a very small proportion of the diverse species currently known in the seas of the world. Sponges may also be found in lakes and rivers.

Today, we know of more than 8000 species of sponges throughout the world (Axinella polypoides, Axinella vaceleti, Aplysina aerophoba, Baikalospongia...), with the Mediterranean accounting for approximately 10%.
Sponges may be bulky, spherical or tree-like, or appear as incrustations. They can vary in thickness and are found in all colours, with a single species being able to vary in shape and colour depending on its habitat. Sponges are described as 'PLASTIC' – this means that their appearance may vary greatly, depending in particular on their environment (light levels, hydrodynamics, etc.)
For more information, visit the World Porifera Database

Sponges are animals, fixed in the adult state (the larvae actually swim), and their whole body is adapted to filter large volumes of water. They are therefore active filter feeders, creating currents in the water, and gain their nourishment by retaining microscopic particles (detritus, bacteria, micro-algae) suspended in the water. Sponges are therefore suspensivores.
Sponges have no tissue or organs, and the filtration of water is carried out by their aquifer system: channels and small chambers lined with specialised cells (choanocytes) that create currents of water and retain nutritive particles (Organisation of the sponge).

Sponges have few predators. We know of many sea slugs that derive nourishment from grazing on the surface of sponges (Sea slug).

Sponges reproduce by both sexual and asexual means. They produce spermatozoa and ovocytes, but do not have reproductive organs. Fertilisation is difficult to observe. It may take place in seawater or in the mother sponge. In the latter case, the spermatozoa are carried to the mother sponge by currents of water. Embryonic development generally takes several weeks and results in swimming larvae (larvae). Sponges may be hermaphrodite (with a single individual producing both spermatozoa and ovocytes) or gonochoric (separate sexes).
Under certain conditions (on occasion, stress) sponges are capable of producing buds, which lead to a new sponge (buds). This is asexual reproduction.
When cut or partially torn away (or nibbled), sponges are capable of forming scars and regenerating their lost parts. This property makes possible the practise of spongiculture (spongiculture).

The trade distinguishes 400 varieties of sponge, but in fact there only exist some twenty species (in the scientific sense) that are marketed worldwide. The main commercial species belong to the family spongiidae and the genera Spongia, Hippospongia, and Coscinoderma.
The special characteristic of these sponges lies in their skeleton, which consists of fibres of spongine, a sort of collagen, which gives these sponges "suppleness, elasticity, and softness".

Hippospongia communis (Lamarck, 1814), the common or "honey comb" sponge, is the species most often caught in the Mediterranean. It may grow very large (several dozen centimetres in diameter). Its network of channels is the most "cavernous", giving it a remarkable power of absorption (Hippospongia communis).

Spongia officinalis Linnaeus (1759), the "fine" sponge, is a frequently caught Mediterranean species, varying greatly in shape and size and with a very fine skeleton, worthy of note (Link to uses). Specialists recognise several Mediterranean varieties – adriatica and mollissima, respectively the 'fine' of the Adriatic (and the Western Mediterranean) and the Syrian 'fine' (from the Eastern Mediterranean). Actually, this is a priori a case of a single species (Spongia officinalis).

Spongia lamella (Schulze, 1879), the Mediterranean elephant ear sponge, for a long time known as Spongia agaricina, which is in fact a species from the Indian Ocean. This sponge has a highly characteristic shape, preventing confusion when it reaches adult size. Its skeleton is extremely fine (Spongia lamella).

Spongia zimocca (Schmidt, 1862), the "trismouche", is a species that is only found in the Eastern Mediterranean, growing in highly unusual shapes, with an extremely fine skeleton

Recognising and catching sponges is a specialised business. There are numerous species with very similar shapes and colours to those of commercial sponges (Scalarispongia scalaris,Ircinia oros, Sarcotragus sp.). What distinguishes them is the nature of the spongine skeleton, which makes these other species unsuitable for any use whatsoever. What is more, as is the case with commercial varieties, these sponges are threatened by environmental disturbances.
Amateurs – hands off, please!

Exploration of the marine environment as a potential source of natural bioactive products with highly original structures is booming. The ocean, which covers 70% of the Earth's surface, is home to almost half the total biodiversity of our planet. To date, more than 6500 natural molecules have been isolated from marine organisms, with sponges accounting for one-third of this resource. For the moment, only 1% of these molecules display any potential in pharmacological terms. So far, four medicines of marine origin have been marketed, and some fifteen other possible candidates are in the various stages of clinical trials prior to the development of medications.