CONTROL or CORAL REEFS BY BORING SPONGES 27 



fore-reef slope habitat at depths between 30 and 70 meters drew 

 our attention to tlie existence of major imdescribed erosional fea- 

 tures which are determined by the activity of boring sponges under 

 conditions where CaCOa deposition in corals is not so fast as at the 

 surface and the effect of wave turbulence is normally negligible. 

 In such localities the consequences of sponge boring go far beyond 

 the mere hollowing out of a few cavities: our observations show 

 that the ecologv of the reef coral population, the movement of reef 

 sediments, and the modeling of the reef edge are all strongly in- 

 fluenced. 



Nassonow's important work (1883) showing that clionid sponges 

 produce fine calcareous debris in the course of their boring ac- 

 tivities has been generallv overlooked, and more recent authors 

 (Revelle and Fairbridge, 1957; Ginsburg, 1957; Cloud, 1959) assert 

 that sponges bore by chemical action and imply that all the ex- 

 cavated carbonate is removed by solution. The observations of Nas- 

 sonow and others suggest, however, that the burrowing sponges 

 may be of major significance in the reduction of reef limestone to 

 verv fine detritus. 



Fig. 1. Incurrent and excurrent papillae of boring stage of Cliona cclata 

 Grant. Oscule in vipper right. (X 3.6.) (From Hartman, 1958.) 



Fig. 2. Massive, free-living stage of Cliona celata Grant. (X 0.36.) (From 

 Hartman, 1958.) 



Fig. 3. Broken edge of a colonv of the coral Agaricia showing extensive 

 excavation bv Cliona tampa de Lau'benfels. (X 0.9.) 38 meters, Maria Buena 

 Bay, Jamaica. (Photo by T. F. Goreau.) 



Fig. 4. Surface of colonv of Agaricia showing incurrent and excurrent 

 papillae of Cliona lampa de Laubenfels. An expanded incurrent papilla may 

 be seen in the upper right; papillae with central holes are excurrent. (X 1.2.) 

 38 meters, Maria Buena Bay, Jamaica. (Photo by T. F. Goreau.) 



Fig. 5. Broken edge of a colony of Montastrea annularis (E. and S.) ex- 

 cavated by a clionid. Beneath the coral polyp layer at the top is a layer of 

 boring algae, seen as a dark line. The boring sponge has died and has left 

 extensive galleries in the coral. (X 0.9.) 38 meters, Maria Buena Bay, Jamaica." 

 (Photo by T. F. Goreau.) 



Fig. 6.' Larva of Cliona spreading out over a fragment of oyster shell. Lines 

 etched into the calcareous matter are clearly seen. (From Nassonow, 1883.) 



Fig. 7. Pattern of depressions left in an oyster shell after the removal of 

 calcareous chips by a clionid. (From Nassonow, 1883.) 



