264 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



It seems fairly certain that any solid food used 

 by the sponge must be very small in size and that 

 it is carried into the flagellated chambers by the 

 internal water circulation. The large quantities 

 of bacteria found in the calcareous muds of the 

 Bahamas in the vicinity of commercial sponges 

 suggests that these organisms may be an impor- 

 tant constituent of the food of these sponges. 

 It has been suggested, however, that sponges may 

 also be able to absorb dissolved organic nutrients. 



Very little is known about the physiology of 

 commercial sponges. Bidder (1923), Parker 

 (1914), and others have studied the water cur- 

 rents. These are set up by movements of the 

 flagella of the choanocytes. These appear to 

 operate independently of each other. The enor- 

 mous number of flagellated chambers provides the 

 energy whereby a considerable volume of water 

 is pumped through the sponge. In noncommer- 

 cial species, such as Spinosella, it has been shown 

 that although the volume of water is great, the 

 pressure does not amount to more than 5 mm. 

 in height of water. The jet stream leaving the 

 osculum may be detected at several inches dis- 

 tance and is sufficient so that on a calm day a 

 distinct disturbance of the water surface may be 

 seen above commercial sponges which are near 

 to the surface. The oscula may be closed by 

 muscular action when stimulated locally. 



Bergmann (1949) and his associates have de- 

 scribed in a series of papers the extraction of 

 sterols from sponges. There is a considerable 

 degree of specificity in the type of sterol found in 

 various sponges, and this bears a close relation 

 to taxonomic classification. Although the com- 

 mercial sponges-'so far investigated have a high 

 fat content, the sterol content of the unsaponifi- 

 able matter is lower than the average. The sterols 

 of commercial sponges have not yet been ana- 

 lyzed in detail. 



Commercial sponges are typically found asso- 

 ciated with muddy bottom sediments, particu- 

 larly where rocky outcrops or reefs provide a 

 suitable substrate upon which the larva can settle 

 without being destroyed by silt. They are some- 

 times found growing attached to dead corals or 

 gorgonians and may occasionallj' grow upon living 

 green algae, such as Penicillus. Under these con- 

 ditions the alga may eventually become com- 

 pletely imbedded in the sponge except for the 

 lower portion of its stalk. 



Commercial sponges appear to flourish where 

 there is a good flow of water but not under very 

 exposed conditions. They are rarely found upon 

 bottoms consisting entirely of rock or, of course, 

 sediments. In the Gulf of Mexico they are found 

 down to a depth of at least 150 feet and in water 

 close to low tide mark. They are not tolerant 

 to reduced salinity except for short periods. They 

 appear to be more resistant to temperature 

 changes, however. 



A considerable number of other organisms are 

 associated with sponges. The surface is frequently 

 covered with encrusting Bryozoa and colonial 

 tunicates. All species of the piling fauna normally 

 found in the vicinity may be epizoic upon com- 

 merical sponges. The green alga, Batophora 

 oerstedi, and species of Acetabularia also become 

 attached to the sponge surface. The starfish, 

 Echinaster, is sometimes observed upon sponges 

 which have lesions of the outer skin, but it is not 

 certain to what extent the damage is caused by 

 this animal. Nudibranchs are sometimes found in 

 small pits or irregularities of the surface, and it is 

 possible that they may feed upon the sponge 

 tissue. Larger holes may be mhabited by various 

 species of small crabs. Dromia is often a perma- 

 nent inhabitant of such places. The green alga, 

 Dictyosphaeriafavulosa, grows in convenient niches 

 and may become almost enclosed by the subse- 

 quent growth of the sponge. A number of the 

 smaller and commoner gastropods are also found 

 inhabiting cavities of the sponge surface which 

 may have been caused by local necrosis, the 

 activities of carnivores or overgrowth of the 

 sponge around sedentary organisms. The barna- 

 cle, Balanus dedivis, which is more commonly 

 found in noncommercial species of sponges, is 

 occasionally seen imbedded in the surface of 

 commercial tj'pes. 



A considerable fauna inhabits the larger passages 

 of the canal S3'stem. Pearse (1934) lists a large 

 ninnber of organisms inhabiting a reef sponge at 

 Dry Tortugas. The most commonly found in all 

 commercial sponges are the snapping shrimp, 

 Syvalpheus brooksi. and the polychaete worm, 

 Leodice spongicola. Other species of polychaetes 

 are also found, particularly syllids and occasionally 

 Amphitrite. 



Among other Crustacea occurring here are the 

 pontonid shrimp, Coralliocaris pearsei, and num- 

 erous amphipods of the genera, Leucothoe and 



