For most divers, a sponge is a very un - extraordinary creature which sits on a rock and sucks!
This may be so, but when you think that they have been doing this for some 650,000,000 years, perhaps there might be a little more to sponges than meets the eye?
What other creature is there that you can cut up into a thousands pieces, pulverise with a hammer, squeeze the mash through a stocking, place the residue into a container of salt water and have it reform into back into itself?
Giant Barrel Sponges Xestospongia testudinaria are part of the normal underwater landscape across a wide area of the Indo Pacific. This species is a Siliceous sponge which may grow to 2 metres in size.
(Photo Neville Coleman)
Sponges are some of the most colourful creatures in the World of Water. These encrusting forms are covering the underside of a large Turbinaria sp. coral in Milne Bay, Papua New Guinea.
(Photo Neville Coleman)
Within the Animal Kingdom, sponges are placed into the PHYLUM Porifera, which contains two CLASSES.
SILICEOUS SPONGES
All the Siliceous sponges are in the CLASS Demospongiae .
Siliceous sponges have fibrous skeletons made up of tough keratin- like material called spongin, which is very resistant to decomposition. The spicules of Siliceous sponges are made of silica.
Another well known and published siliceous sponge is the Violet Ball Sponge Cinachyra tenuivolacea. This species is often seen at Heron Island, Great Barrier Reef in depths of 10 to 30 metres.
(Photo Neville Coleman)
The Orange Crumble Sponge Acarnus sp. can grow to 250 in height and is a resident of reefs in the Maldives and the Indian Ocean. This is a siliceous sponge and has silica spicules.
(Photo Neville Coleman)
CALCAREOUS SPONGES:
All the Calcareous sponges are placed into the CLASS Calcarea. There are less species of Calcareous sponges, and in general they yellow, white, or light brown in colour.
Calcareous sponges have spicules comprised of lime (calcium carbonate) and these sponges have no spongin fibres in their skeletons.
Known visually for many years, the Volcano Sponge Pericharax heteroraphis is found throughout the Great Barrier Reef. This species is a calcareous sponge and is fed upon by various nudibranchs.
(Photo Neville Coleman)
A classic Calcareous sponge is the bright yellow Chago Sponge Leucetta chagosensis from the Maldives and the Indian Ocean.
(Photo Neville Coleman)
The little white Tangled Sponge Sycetta sp. only grows to around 70 mm and is a fragile member of the calcareous sponge class.
(Photo Neville Coleman)
SPONGE FEATURES
Close up of the Veined Sponge Clathria ( Microciona) mima shows an excellent picture of how the insides of some sponges work, as it has some of its channels on its surface.
(Photo Neville Coleman)
Sponges are considered by some to be the first multicellular animals; their fossil remains have been traced back to the Precambrian era, some 650,000,000 years ago. These simple, primitive life forms are widespread throughout temperate and tropical seas, with over 15,000 species known worldwide.
Very strange in form is the Labarinth Sponge Luffariella sp. from Sorrento Reef off Sorrento, Perth, Western Australia.
(Photo Neville Coleman)
Sponges are individual animals ( not colonies) covered by a thin skin which houses multitudes of roving cells. They have no specific body plan and may form into any shape determined by their habitat and may be soft, or firm in texture.
The body is perforated by pores and canals; with or without fibrous skeleton, and the body mass is supported internally by characteristically shaped, non attached spicules.
The huge flabby forms of the giant yellow sponge Ianthella basta grow almost to 2 metres and are found along the reef edges and slopes in Milne Bay, Papua New Guinea.
(Photo Neville Coleman)
They are without intestines, and have no nervous systems.
Most sponges have a fibrous skeleton that is made up of a keratin like material called spongin, which is only found in sponges.
Spongin is very resistant to decomposition and that is the reason why so many sponge skeletons washed up on beaches, remain there for many years before breaking down.
LIFESTYLE
Sponges can be found on coral reefs, rocky reefs, on rubble, sand, mud and every micro habitat in between. Depending on the environment a single species may develop into an encrusting form in areas open to rough seas, or may grow upright and branched in sheltered areas, or deeper water.
Colour is also variable; a sponge that grows in the shade, may be a different colour to the same species growing in the sunlight. All sponges are attached, or anchored to the substrate.
New Zealands sponge fauna is well documented and published. Golden Ball Sponges Tethya aurantium are very common in the North Island and these were taken at Leigh.
(Photo Neville Coleman)
Most appear to prefer hard substrate, though some live on soft bottom, imbedded into sand, or mud.
There are commensal sponges that live on the valves of bivalves and univalves, others bore holes in shells, rocks and coral, and those which specialise in dissolving living tissue and living corals.
Sponges range in size from minute encrusting species only seen beneath rocks, to massive structures up to two metres high living in very deep water. The largest I have ever seen has been a little over 1.5 metres in height.
Papua New Guinea has an amazing sponge fauna which has taken many years to discover. A great deal of work has been done at the Motupore Research Station , near Loloata Dive Resort in Bootless Bay. The Paradox Sponge Liosina paradoxa is one of those which lend themselves to visual identification.
(Photo Neville Coleman)
The anatomy of a sponge is complex, but in general the body is perforated by many small inhalant pores, called ostia. Also present is one or more larger exhalent pores, called oscula. Inside the complex body, these pores are connected by converging channels which pass through the sponge tissue. These channels are lined to some extent by special cells called collar cells and these collar cells bears a single filament ( tail like process) , or flagellum which beats, driving a steady stream of water through the sponges ostia, supplying it with food and oxygen, and then driving the stream of waste water out through the oscula opening, or openings.
One small sponge no bigger than a clenched fist can filter its own body volume of water every 4 to 20 seconds, which amounts to around 5000 litres in one day.
Described for its resemblance to a candelabra, the Candlebra Sponge Pipestela candelabra is known from Papua New Guinea and to my experience , yellow is its only colour form.
(Photo Neville Coleman)
REPRODUCTION
Sponges can reproduce sexually, or asexually, and most are hermaphrodites, having male and female sex cells. Sperm are shed into the water through the exhalant oscula. When sperm are taken in by sponges of the same species through their inhalant ostia, fertilisation occurs. The resultant larvae leave by way of the exhalant oscula and settle to the bottom to develop into a new sponge.
Small pieces budded off, ( gemules) can also grow into an adult animal.
ASSOCIATION
Due to their needle sharp spicules, tough bodies and highly toxic chemical deterrents, sponges have few predators. However, they are food of choice for hundreds of species of nudibranchs, umbrella shells, sea stars, and sea urchins. Some nudibranchs retain the toxic chemicals in the tissues of their own bodies and in this way avoid predation by fish. Quite a number of small invertebrate live, or hide in sponges. Spider crabs and sponge crabs utilise pieces of sponges to protect themselves from enemies.
This Orange Sponge Haliclona sp. from Rottnest Island off Perth, Western Australia has been infested by an enctrusting zoanthid. Some of the small polyps of the zoanthid can be seen expanded during the day, but most would come out at night.
(Photo Neville Coleman)
The Coral eating Sponge Haliclona nematifera appears to absorb the living coral tissue, sometimes it grows over the dead space, and sometimes it just moves as a growing edge. The green colour shows how quickly algae moves onto the new space on the dead coral.
(Photo Neville Coleman)
IDENTIFICATION
Unfortunately much of the original sponge identifications were made on dead specimens last century and was very difficult for me to set up a visual identification guide to Australian sponges as it was not seen to be beneficial.
However, due to the chemistry of sponges coming into the forefront of marine pharmacology, scientists have been able to obtain grants to enable the sponge fauna to be readdressed and sorted out taxonomically, with newer, live collected specimens.
Diving scientists have also utilised underwater photography, integrating it into the Museum system, establishing the images with preserved and identified specimens. Many new species have been discovered in the process.
As a result, many species of sponges are now able to be identified visually and at long last I can include more than a couple of sponges in each book.
I am grateful to the Queensland Museum sponge department for allowing me to house specimens in their archives and to supply me with identifications.
Museum taxonomists have huge numbers of specimens to identify from all over the world, as well as hundreds from their own regular field trips, so it is no small thing to make time for extra work.
I have been photographing sponges and trying to build a visual index to living sponges for 40 years and it is gratifying to see that the once maligned, very smelly sponge, (as specimens) can finally be presented in all their glory as a very important part of the oceans biodiversity.
Copyright Neville Coleman