Sponges of the New Caledonian lagoon - IRD

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Sponge.
of the New
Caledonian
Lagoon
are still centred around the Mediterranean and Caribbean although there are several
commercial or potentially commercial "bath" sponge species in the Pacific.
In the past there have been attempts to harvest commercial sponges throughout
the Indo-Pacific. with active fisheries at the turn of the century in northern Australia.
Indonesia and parts of Southeast Asia. but in all cases. so far. the Pacific commercial
sponges only occur in small populations and only provide a mediocre quality
commercial producT. Nevertheless. there are still some active sponge fisheries in
this region. particularly harvesting of wild popuJations in the Philippines and an
attempt at a commercial farm. culturing sponges. in Pohnpei in Micronesia. but no
such attempt has yet been made in New Caledonia. There are two potentially com­
mercial species in the New Caledonian lagoon. Spongio oustro}is and
Coscinodermo mothewsi. but these are neither abundant nor of sufficient quality to
support a wild-harvest commercial industry.
There are three major classes of Porifera: Calcarea or calcareous sponges.
Hexactinellida or glass sponges and Demospongiae or siliceous sponges.
Hexactinellida. or glass sponges. have substantially different structure and function
than the other two classes. now recognised as distinct from the other two at the
subphylum level. But most of these glass sponges live in deep waters, inaccessible
to divers. and consequently they are not dealt with in this book. Calcarea are primarily
found in shallow waters, particularly abundant and diverse in coral reefs.
Demospongiae, which represent most of the liVing species today, can be found at
all levels in the sea and also in fresh water, with large populations known from
some rivers and lakes.
Porifera have had a long geological history. Most of today'S liVing species can be
traced back directly to ancestors living in the mesozoic terrains from the Jurassic
(208- 144 million years ago) and Cretaceous eras (144-66 mya), but some can be traced
back to the Cambrian era (570-505 mya). conversely. other sponge groups that
existed during the ancient palaeozoic eras (older than 250 mya) totally disappeared
during the Permian-Triassic crisis (260-225 mya). Many fossil sponges, particularly
those with rigid-bodied composed of interlocking spicules Clithistid" sponges). show
well preserved skeletons in the fossil record. But for the most part these fossils
belong to minor groups. and most soft-bodied sponges had poor fossilisation
potential. Their Skeletons disintegrated before fossilisation occurred, and for many
of these groups we lack definitive information to track their history.