Figure 17. — Cross section of a wool sponge with hole occupied by a sponge crab, Pilumnus 

 sayi. The surface of the interior of the cavity is smooth and shows no sign that the 

 crab eats any of the sponge material. Around the edge of the sponge, bare fibers of 

 spongin material have been exposed by the withdrawal of living material of the sponge, 

 probably as a result of sudden lowering of the water temperature. See section on tem- 

 perature relationship for details. 



is sometimes found imbedded in the surface of 

 commercial sponges but is more commonly 

 found on the noncommercial species. 



Large numbers of developing larval forms of 

 a tunicate were found attached to the walls of 

 the canals in almost all of some 200 wool 

 sponges examined microscopically. These 

 were microscopic in size and were not identi- 

 fied. Larger colonial tunicates often attach and 

 grow on the top or sides of the sponge, usually 

 affecting the shape. 



Many small snails, key hole limpets, and 

 small bivalves are found in the mass of the 

 sponge apparently surrounded by the sponge as 

 it grows. These animals are also found in the 

 canals of the sponge into which they have 

 crawled in their search for food. The spongers 

 believe that some species of the key hole 

 limpet eat and damage the sponge. Nudi- 

 branchs have also been found on the surface 



of the sponge, especially in the surface depres- 

 sions. These may also occasionally feed on the 

 sponge tissue. The basal portion of the sponge 

 often contains the open-coiled shells of the 

 snail Vermetus. Fish fry may occupy the canals 

 of the sponges. 



I have noted that many of the finger sponges 

 bore the teeth marks of fish. The stomach con- 

 tents of the spadefish, Chaetodipterus faber, shoW 

 that this fish may be responsible for damage to 

 finger sponges. Several other unknown species 

 of fish must also eat this sponge. There is no 

 evidence that any of the other commercial 

 species of sponges are damaged by any fish. 



The association of many plant or animal 

 forms with the commercial sponges is ap- 

 parently fortuitous. Almost any small plant will 

 attach to the surface, and almost any small 

 animal that either normally attaches to an 

 object on the bottom or else seeks shelter in a 

 protected cavity will live on or in the sponge. 



50 



