Deep-sea sponge reaches out, devours.Most people think sponges spend their days quietly sucking in and spitting out water, hoping to trap a few bacteria or some organic matter in their filters for dinner. A newly identified sponge may send this picture of passivity down the drain. Jean Vacelet and Nicole Boury-Esnault of the Universite d' Aix-Marseille II in Marseille Marseille or Marseilles City (pop., 1999: city, 797,486; metro. area, 1,349,772), southeastern France. One of the Mediterranean's major seaports and the second largest city in France, it is located on the Gulf of Lion, west of the French Riviera. , France, discovered a sponge that has evolved some, shall we say, unique characteristics in response to the scarcity Scarcity The basic economic problem which arises from people having unlimited wants while there are and always will be limited resources. Because of scarcity, various economic decisions must be made to allocate resources efficiently. of food in the relatively still waters of the deep sea, they report in the Jan. 26 NATURE. "This remarkable sponge is effectively a carnivore carnivore (kär`nəvôr'), term commonly applied to any animal whose diet consists wholly or largely of animal matter. In animal systematics it refers to members of the mammalian order Carnivora (see Chordata). ," Michelle Kelly-Borges of the Natural History Museum in London notes in an accompanying editorial. The sponge has developed filaments to capture small crustaceans. Minute, hook-shaped, pointy point·y adj. point·i·er, point·i·est Having an end tapering to a point. structures called spicules cover the moveable filaments and provide "a Velcro-like adhesiveness," the authors say. Crustaceans, usually less than 1 millimeter wide, get trapped on the spicules. They struggle for hours to free themselves. Then new filaments grow over the prey, covering it completely in a day. Within a few days, the sponge digests its catch. Most of this food is broken down within the sponge's body, but the filaments can digest little nibbles, Vacelet explains. The as-yet-unnamed sponge belongs to the genus genus, in taxonomy: see classification. genus Biological classification. It ranks below family and above species, consisting of structurally or phylogenetically (see Asbestopluma, which normally resides in the North Pacific and North Atlantic at least 100 meters below sea level. Indeed, members of this genus live as far down as 8,840 meters. However, Vacelet and Boury-Esnault found their specimen a mere 17 meters below sea level, in a Mediterranean cave. No one knows for certain how the sponge got there. Perhaps strong currents carried it from a deep-sea canyon. In any case, the cave had all the attributes of the deep sea: cold water, limited nutrients, and darkness, Kelly-Borges notes. Researchers had suspected that deep-sea and shallow-water sponges had different systems for capturing their dinner. Scientists had even seen sponges with spicules. However, they knew little about the deep-sea dwellers or what the spicules did. The cave discovery "made it possible to observe for the first time how sponges feed in such extreme environments," the French scientists report. Normal sponges "are filter feeders filter feeder n. An aquatic animal, such as a clam, barnacle, or sponge, that feeds by filtering particulate organic material from water. filter feeder par excellence. Their entire body is organized for filtering water, which is moved inside an aquiferous aq·ui·fer n. An underground bed or layer of earth, gravel, or porous stone that yields water. a·quif  er·ous adj.Adj. system by choanocytes," or pumping cells. The new sponge has neither choanocytes nor a system for filtering water. "The definition of the phylum phylum, in taxonomy: see classification. , based on the aquiferous system and . . . choanocytes, is now inadequate," Vacelet says. |
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