MARSEILLE, FRANCE- The discovery of crustacean-crunching sponge in the shallows of the Mediterranean Sea has surprised marine biologists and confused taxonomists.

Researchers from the Marseille Center of Oceanography discovered the new species in a cave at a depth of about 20 meters. Upon initial observation the sponge more closely resembled deep-sea cladorhizid sponges than the type found closer to the surface which is still used today for scrubbing off dirt in the bathtub. Indeed, the new species appears to belong to the genus Asbestopluma which holds the depth record for all genera of sponges, 8,840 meters.

The typical sponge is a filter feeder, pumping water through an aquiferous system via specialized cells called choanocytes. The new species is devoid of both the choanocytes and the aquiferous system. Since it lacked the tubes and tunnels that most sponges use to filter-feed, the researchers wondered how it fed itself.

Anatomic and biological analysis of both living and preserved specimens revealed the presence of spiky filaments with raised hook-shaped spicules. At first the researchers thought the newly discovered sponge fed on dissolved organic matter by passive phagocytosis, as do some of it deep-sea cousins. However, subsequent analysis showed the presence of minute crustaceans caught within the filaments.

"Once captive, the crustaceans were unable to free themselves. They remained struggling for several hours, which indicates that there was no paralyzing or toxic secretion. New, thin filaments grew over the prey, which was completely enveloped after one day and digested within a few days,'' notes Jean Vacelet, University of Aix, Marseille.

The discovery of the new sponge raises fundamental questions about current classifications used to distinguish the phyla of lower invertebrates, since is lacks many of the basic attributes of known sponges. Were it not for its resemblance to several species of Porifera it might qualify for recognition as a distinct phylum. Rather, it appears the novel creature is a sponge that has developed several adaptations to accommodate to its environment, he noted

Sponges- phylum Porifera, are sometimes considered an evolutionary dead end since no other animal groups are derived from them. Biologists are still divided on whether the sponge is a true multicellular organism or a colony of cells. Interestingly, if the individual cells of a living sponge are separated and then mixed together again, the cells will reassemble into the original organized shape.

For more details please see Nature, v.373, 1/26/95, Vacelet et al.

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