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 | |  | | | A new species of Echinochalina sponge discovered by the Queensland Museum during biodiversity studies. | | |
Sessile Marine Invertebrates
Dr John Hooper
Dr Merrick Ekins
Ms Monika Schlacher-Hoenlinger
Dr Patricia Mather
Section
Many organisms on the seabed, particularly in soft sediments, are sponges, but they are still relatively unknown. There are about 15,000 species worldwide with about one-third of these living in Australian waters. Since 1994, we have discovered more than 1000 species new to science. In addition to their ecological importance in reef systems and on the soft seabed, these animals are exciting sources of new therapeutic compounds with potential values to the pharmaceutical industry.
Our current work
- Biodiversity of sessile marine invertebrates and bioprospecting for natural therapeutic compounds as sources of potential pharmaceuticals (funded by AstraZenica R & D Griffith University (AzGu)).
- Biodiversity, molecular phylogeny and ultrastructural studies of Calcarean sponges from the GBR (funded by the Australian Biological Resources Study and AzGu).
- Seabed biodiversity on the continental shelf of the GBR World Heritage Area (funded by CRC Coral Reef Centre, in collaboration with CSIRO Marine Research and the Australian Institute of Marine Science) (commencing 1 July 2001).
- Discovering Queensland’s Relict Marine Fauna. Submersible project to explore the deep shelf and upper bathyal of the GBR and Queensland Plateau (Project QLSUB) (funded by AzGu in partnership with the University of Goettingen, Germany) (planning commencing February 2001).
- Taxonomy, systematics, phylogeny and biogeography of tropical Australasian demosponges, ascidians, soft corals and gorgonians (funded by the Queensland Museum and Australian Biological Resources Study grants)(ongoing)
Significance
Sponges in particular, and sessile marine invertebrates in general, are proving to be extremely valuable and potentially economically important sources of compounds useful to the pharmaceutical industry, and it is this industry funding our research. Sponges are also ecologically significant, being the second most common (and diverse) group of animals in coral reefs, and sometimes the most common group of animals living in between reefs.
Guide to the collections
With the Great Barrier Reef our most important marine biodiversity resource, the museum has a strong focus on marine invertebrates, particularly those sessile species living attached to the seabed. The Museum has large collections of the various sessile marine invertebrate phyla, with over 32,000 specimens held in the Southbank and 28,000 in the Townsville (Museum of Tropical Queensland) facilities. Together these collections are recognised internationally for their comprehensive coverage of Indo-west Pacific species of sponges, hard corals and ascidians (tunicates), with more recent additions of world-class collections of ‘jellyfish’ (marine stingers [hydro- and cubomedusae]). The Southbank SMI collections consist of approximately 700 types and collections are 98% databased, with over 2000 undescribed species in collections.
FAQ
Download the Guide to Sponge Collection and Identification (580kB Acrobat® pdf file). (Requires the free adobe acrobat® reader.)
Q:
How many species of sponges are there ?
A:
Frankly, we don't really know the magnitude of sponge biodiversity, but we have some theories ...
In some habitats sponges are the dominant macrobenthic life form; in others they are very scarse.
Some places in the world have a relatively well-known sponge faunas (e.g. Mediterranean, Caribbean, British Isles), basically reflecting the relatively long period of time scientists have worked on these faunas. Each of these regions contains about 500-800 species, with no more than about 100 species shared between the regions (i.e. so-called 'cosmopolitan species').
Some areas have moderately well known faunas (e.g. Madagascar, New Caledonia, New Zealand, Sri Lanka, Micronesia, Japan) mainly as a consequence of recent scientific exploration during the past 20 years or so. Each of these regions probably has between 400-600 species, with about 100 shared species at most.
Other places have poorly known sponge faunas, and (worse still) most of our knowledge is from old expeditions (pre-1900s; which makes 'data' even more dubious). These areas include Australia, Indonesia, Papua New Guinea and other parts of the Indo-Malay archipelago. However, it is well known from studies on other groups of animals that this region has the highest proportion of the world's marine biodiversity, and there is no reason to show us that this is different for sponges.
Worldwide: In the literature there are about 7,000 'valid' species published worldwide, BUT we estimate that there are at least 15,000 living species in all the world's seas and lakes.
Australia: In Australia there are about 1,400 species described in the scientific literature, but we estimate that there are probably at least 5,000 species living in continental and territorial waters. We know this because currently our collections contain about 4,000 species of sponges, mostly Australian, with most (about 2,000) new to science and requiring descriptions and naming in the scientific literature. We haven’t yet begun to look comprehensively at the cryptic and encrusting fauna which is probably as equally diverse as the macrobenthic fauna. Documenting and describing biodiversity is a long, time consuming process that requires accuracy and patience, but it is an essential prerequiste to conservation and management of our marine resources.
Indo-Malay Archipelago and South China Sea: There are approximately 1,200 described species of sponges known from the South China Sea region (extending from Cocos, Nicobar and Andaman Islands, the Andaman Sea, islands and coast of Burma, west coasts of Thailand and the Malay Peninsula, Singapore, islands and waters of the Straits of Malacca, all the islands of the Indonesian Archipelago, the Gulf of Siam, east coast of the Malay Peninsula, Thailand, Cambodia, Vietnam; Borneo, Sarawak, Sabah, Brunei; southern China, Hong Kong; Philippines, Palawan. (This excludes Papua New Guinea and northern Australia) which have largely different sponge faunas. However, it is thought (with some justification) that this region may contain a very high diversity, perhaps in the order of 4,000-6,000 species, but it is probably also the least comprehensively documented fauna by modern standards given that most of our knowledge of the fauna derives from pre- and early 1900 literature (plus generally unreliable identifications made by collectors for chemical studies).
Q:
What are sponges and what makes them unique ?
A:
Sponges are the most primitive of multicellular animals (metazoa), belonging
to the Phylum Porifera.
The Phylum Porifera has four classes: Archaeocyatha (all extinct),
Demospongiae (having siliceous spicules (opaline or anhydrous silicate) and/ or
proteinaceous fibres, and includes the commercial ‘bath’ sponges), Calcarea
(sponges with spicules composed of calcium carbonate) and Hexactinellida (the
glass sponges, also with siliceous spicules).
They have a cellular grade of construction without true tissues. Body plans
range from simple (asconoid, syconoid) through to complex (leuconoid) produced
by varying degrees of infolding of the body wall and complexity of water canals
throughout the sponge.
Adults are asymmetrical or radially symmetrical.
Sponges are exclusively aquatic (water dwelling), most marine, found from
deepest oceans to the edge of the sea.
Sponges play such important roles in so many marine habitats but we still
know very little about their diversity, biology and ecology as compared with
most other animal groups. In many benthic (sea bottom) habitats sponges are
often the dominant animals.
Sponges have evolved an amazing range of growth forms, best described as
highly irregular and sometimes completely plastic, frequently altered by
prevailing external conditions (currents, turbidity, salinity etc.). Sponges
also have evolved an amazing array of colours (possibly linked to
photoprotection ?)
Adult sponges are sedentary (sessile), attached to the seabed or other
substrate for most of their lives, although many have larvae that motile,
swimming or crawling away from their parent.
Sponges have sexes that are separate, or sequencially hermaphroditic,
although most population dispersal and recruitment is asexual (through budding,
fragmentation from storm events, etc).
Larvae are motile, incubated within the parent or broadcast into the
seawater: parenchymella (solid, ciliated), amphiblastula (central cavity).
Sponges filter sea water to eat, breath and excrete waste products. Sponges
often have complex water canal systems running throughout the body, with smaller
inhalant (ostia) and larger exhalant pores (oscules). Sponges are able to
actively pump up to 10 times their body volume each hour, making them the most
efficient vacuum cleaners of the sea.
Sponges appear to be very stable, long-lived animals, although growth rates
vary enormously between different groups. Some sponges, like haplosclerids can
grow centimetres in weeks, and may have shorter life spans. Others sponges, like
the living fossil 'sclerosponges' are VERY slow growing, with the largest known
individuals (up to 30cm diameter) thought to be around 5,000 years old (which
makes them the oldest living individuals on the planet, if this is true !).
Sponges are a unique group of animals because ....
Sponges have unique collar-cells (choanocytes) which are surrounded by cilia
with a central flagellum that moves to actively create a current pulling water
in and out of the sponge. These collar cells line the walls of small chambers
throughout the water vascular system. There may be 7,000-18,000 of these
chambers per cubic millimeter of sponge, and each chamber may pump approximately
1,200 times its own volume of water per day !
Sponges have no tissues or sensory organs but they do have MANY different
types of cells with MANY different functions that carry out normal bodily
routines, including a primitive cell type (called an archaeocyte, an
amoeboid-like cell) that is totipotent (able to change functions as required by
the sponge [e.g. secrete the skeleton, form the epidermis, become feeding and
reproductive cells etc.]).
Outer and inner layers of cells (exopinacocytes, basipinacocytes) (="the
skin") lack a basement membrane; middle layer.(mesohyl) is variable but always
includes motile cells and usually some skeletal material.
Mineral skeleton is present in most (but not all) groups of sponges composed
of calcium carbonate, silicon dioxide, and/or collagen fibres.
Skeletal elements (spicules) are diverse in their geometry and size.
Sponges are individuals, having a continuous "skin" (epithelium) that
contains roving cells inside; they are not colonies (like corals and sea-squirts
in which individuals animals group together).
Sponges catch, eat, digest their food and excrete their waste products
within cells, not within any common body cavity, unlike most multicellular
animals.
Some sponges (particularly those growing on coral reefs) have a unique
symbiosis with cyanobacteria not found in any multicellular animal. These
cyanobacteria (or blue-green algae) provide the sponge with nutrients from
photosynthesis to supplement those obtained by the sponge from normal filter
feeding activities. These extra nutrients greatly augments sponge growth rate
and competitive ability in coral reef systems.
Sponges are morphological conservative, with a VERY ancient geological
history they were already well established during the Lower Cambrian (>550
million years ago), and were major reef builders during the Devonian (>370
million years ago) before the reef-building corals "took over" reef formation;
most modern genera and species similar to those around today appeared at the
beginning of the Cretaceous (>150 million years ago).
Q:
What do sponges do ?
A:
Sponges don't appear to do much at all, but in fact they are very active ! Sponges sit on the bottom of the sea actively pumping seawater through their bodies. This water, containing nutrients, is filtered through a series of sieve-like pores (diminishing in size), finally ending up at the collar cells. Nutrients are actively carried across the cell wall, engulfed by archaeocytes, and subsequently transferred throughout the mesohyl.
In addition to “regular food”, this seawater also contains the toxic chemicals excreted by other plants and animals, such as corals growing on the coral reefs above. Sponges feed on these chemicals, modify and reuse them for their own purposes.
Many of these sponge-modified and sponge-produced chemicals have potent toxicity against human pathogens, cancer cells etc., or are useful against certain human ailments (e.g. anti-inflammatory, cardiovascular, respiratory, analgesic etc. properties).
Q:
Why do sponges produce many highly toxic chemicals ?
A:
Sponges are not mobile, and as such they cannot escape from predators (such as fishes, turtles, gastropods, echinoderms, flatworms). They are generally unable to physically defend themselves. Perhaps they use these chemicals to defend themselves ?
Sponges do not have arms or legs and so they cannot physically remove other animals and plants settling on their exterior surfaces and from within water canals. Perhaps they use these chemicals to repel parasites ?
Sponges are generally slow-growing, easily out-competed for space and living resources by other faster growing animals and plants (such as corals and ascidians). Perhaps they use this arsenal of chemicals in a chemical warfare against these faster-growing species ?
Sponges are often full of small animals and microbes, particularly embedded within body cavities and throughout the water canals. Perhaps many of these chemicals are antibiotic to these microbes ?
Some sponges burrow into corals and use chemicals to eat away the calcium, eventually occupying the entire interior surface of the coral (with breathing tubes or fistules poking through the surface). Other sponges grow on top of corals, smothering and eventually eroding the dead coral, and some that bore into oysters and pearl oyster shells killing the animal inside. There are also many sponges that live in between coral branches, at the base of corals and in the substrata surrounding corals that bind the corals together. Perhaps some of these chemicals are important in the continual process of bioerosion of coral reefs and releasing calcium back into the system, and consolidation of dead coral producing stable reef structures ?
Some sponges have intimate, symbiotic relationships with other animals (such as gastropods, hermit crabs, shrimps), or plants (blue-green algae or cyanobacteria), which is frequently species specific. Perhaps these chemicals produce recognition signals between the symbiotic partners ?
Or maybe all of these factors are important ?
Q:
Why is it important to maintain museum collections of sponges, especially those used for medical research, and why is taxonomy (science of identification and evolutionary relationships) important to this process ?
A:
We MUST know the species of sponge from which the 'magic molecule' was discovered, exactly where it was collected, what season it was collected in, and whether there are morphologically similar species living nearby that may be confused with the target species. Museum collections, specimen database, and species 'profile' databases are essential for this process.
A fragment or duplicate 'voucher specimen' of a target species MUST be kept (preserved) in a museum (i.e. separate from the samples analysed chemically or genetically). In sponge taxonomy it is usually always essential to re-check this 'voucher specimen' against new samples to be sure whether it is the same or different. Because there are so many morphologically similar species that are often taxonomically unrelated, and certainly chemically very different, using a published species description is often not adequate by itself to identify a sponge, particularly when the description is pre-1900 (which is largely the situation for the Indo-west Pacific sponge fauna).
Collections and collection databases (containing accurate locality data, accurate descriptions of species' characteristics) are mainly the provinces of museums, providing a unique resource that many other scientists often do not have (e.g. no time to both build the collections and databases, and carry out the target research on these collections) .
The taxonomist's role is to publish these species descriptions and distributions, with the (maybe impossible) aim of FULLY document regional biological resources in a systematic, scientific way.
Good taxonomy underpins every other branch of biological and biochemical science ! Comprehensive, accurate descriptions, with recognisable illustrations and accurate locality data are essential for determining the relationships between species and regions (biogeography), how many species are shared between closer or more distant regions (species' dispersal potential, reproductive mechanisms etc.), habitat preferences (ecology), population variability (genetics) and chemical relationships (chemotaxonomy, marine natural products chemistry).
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