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17. Sponges
J. N. A. Hooper
N OVERVIEW
The Phylum Porifera is the most primitive of the multicellular animals, with a most ancient geological history.
Porifera appeared early in the history of life on Earth,
established in the Proterozoic, with the major Class
Demospongiae first appearing in the Precambrian
Ediacaran age (about 750 million years (My) ago). By
the Middle Cambrian (about 500 My) demosponges
were thriving, and today represent about 85% of all living species. During the massive radiation of life forms
in the Ordovician (490–460 My), and for the next 100 million years or so, sponges formed extensive barrier and
fringing reefs around the ancient continents and were
the primary reef builders in these ancient oceans.
Sponges declined as the primary reef-builders at the
end of the Devonian (350 My), and today they are not
significant reef-builders in shallow waters, unable to
compete with the faster growing zooxanthella-bearing
corals, although several hard-bodied (lithistid and hypercalcified) reef-building groups of sponges persist in
modern day reefs. Although sponges are still a major
component of modern-day coral reef ecosystems they
are often overlooked by the curious naturalist because
they are frequently hidden among the more prominent
corals on the reef, or live in the less frequently visited
deeper waters surrounding reefs. Nevertheless, in terms
of their species diversity, they outnumber both the hard
and soft corals combined. In some habitats they provide
pivotal ecological services, such as significant contributions to coral reef primary productivity, filtration of the
waste products and toxins from other reef organisms,
and major recycling of calcium carbonate back into the
reef system through bioerosion.
N DIVERSITY
Sponges are predominantly marine, living from the intertidal to the abyssal zone, with a small number also
found in freshwater habitats. Worldwide there are approximately 8500 species described in the literature
that are considered to be ‘valid’, with about twice this
number estimated for all oceans. Approximately 1500
species have been described among the Australian
fauna so far, although an escalated collection effort over
the past couple of decades, mainly from tropical and
subtropical waters and spurred on by drug discovery
from marine organisms, has discovered a fauna three
times this size. This work leads to an estimated Australian fauna of at least 5000 species. So far only about
400 species are described in the literature for all Queensland waters, including the coast, the GBR and Coral
Sea island territories. Extensive surveys over the past
two decades, however, reveal that more than 2500
sponge species actually live here, with the majority
remaining undescribed (new species).
Amongst the better known sponge faunas on the
GBR are, not surprisingly, those from the most
17. Sponges
J. N. A. Hooper
N OVERVIEW
The Phylum Porifera is the most primitive of the multicellular animals, with a most ancient geological history.
Porifera appeared early in the history of life on Earth,
established in the Proterozoic, with the major Class
Demospongiae first appearing in the Precambrian
Ediacaran age (about 750 million years (My) ago). By
the Middle Cambrian (about 500 My) demosponges
were thriving, and today represent about 85% of all living species. During the massive radiation of life forms
in the Ordovician (490–460 My), and for the next 100 million years or so, sponges formed extensive barrier and
fringing reefs around the ancient continents and were
the primary reef builders in these ancient oceans.
Sponges declined as the primary reef-builders at the
end of the Devonian (350 My), and today they are not
significant reef-builders in shallow waters, unable to
compete with the faster growing zooxanthella-bearing
corals, although several hard-bodied (lithistid and hypercalcified) reef-building groups of sponges persist in
modern day reefs. Although sponges are still a major
component of modern-day coral reef ecosystems they
are often overlooked by the curious naturalist because
they are frequently hidden among the more prominent
corals on the reef, or live in the less frequently visited
deeper waters surrounding reefs. Nevertheless, in terms
of their species diversity, they outnumber both the hard
and soft corals combined. In some habitats they provide
pivotal ecological services, such as significant contributions to coral reef primary productivity, filtration of the
waste products and toxins from other reef organisms,
and major recycling of calcium carbonate back into the
reef system through bioerosion.
N DIVERSITY
Sponges are predominantly marine, living from the intertidal to the abyssal zone, with a small number also
found in freshwater habitats. Worldwide there are approximately 8500 species described in the literature
that are considered to be ‘valid’, with about twice this
number estimated for all oceans. Approximately 1500
species have been described among the Australian
fauna so far, although an escalated collection effort over
the past couple of decades, mainly from tropical and
subtropical waters and spurred on by drug discovery
from marine organisms, has discovered a fauna three
times this size. This work leads to an estimated Australian fauna of at least 5000 species. So far only about
400 species are described in the literature for all Queensland waters, including the coast, the GBR and Coral
Sea island territories. Extensive surveys over the past
two decades, however, reveal that more than 2500
sponge species actually live here, with the majority
remaining undescribed (new species).
Amongst the better known sponge faunas on the
GBR are, not surprisingly, those from the most