monthly intervals until the experiment was 

 terminated by the sponges' dying during an 

 accidental stoppage of the water flow. 



The effect of temperature on growth is shown 

 by a series of photographs of a whole yellow 

 sponge (fig, 14). The first of these photographs 

 was taken within 4 days after the sponge had 

 been taken from the sea and placed in the 

 aquarium. At that time the temperature range 

 over a period of a week was between 80° F. 

 and 85° F. The appearance of the sponge at this 

 time was normal. 



The second photograph was taken in Decem- 

 ber, almost 3 months from the time the sponges 

 were placed in the aquaria. During this 3- month 

 period the temperature had gradually de- 

 creased to 70° F. Observations made on the 

 sponge at this time showed that there had been 

 an increase in size of almost one-quarter of an 

 inch in diameter. This increase in size was 

 made despite the necessary healing of the 

 sponge base, the change to a much different 

 environment in the aquarium, and probably a 

 lowered food supply. 



The third photograph of the series shown was 

 taken a month later in January 1956, 6 days 

 after the temperature had dropped from 70° F. 

 to 62° F. within a 6-day period. This sudden 

 drop in temperature was the apparent cause 

 for the very considerable withdrawal of living 

 material from theperiphery of the sponge. This 

 withdrawal amounted to more than one- quarter 

 of an inch in places. Close examination of the 

 sponge at this time showed that the "skin "was 

 as healthy at this lower level as before, and 

 the only apparent change was the exposure of 

 the ends of the spongin fibers. The photograph 

 shows clearly that the bared fibers are light in 

 color while in places the healthy "skin" of the 

 animal shows through as black. Within a few 

 months the exposed fibers rotted away and the 

 sponge again appeared normal but reduced in 

 size. 



Similar, but not as severe, withdrawal of 

 tissue inward has been observed during the 

 field studies (fig. 17, p. 50) and in preserved 

 material collected in the winter. A number of 

 sponges have been taken which had the fibers 

 of the conules exposed for one-eighth of an 

 inch or more. 



When the temperature is 80° F, to 90° F,, 

 sudden increases in temperature have been 

 reported by F. G. Walton Smith to be detri- 

 mental to commercial sponges. 



Effect of Water Currents on Sponges 



Mean tidal flow along most of the coast in 

 water depths of 24 feet is about one-half of a 

 knot. The rate of flow is affected by bottom 

 contour and modified considerably by the rate 

 of flow of the inshore current which travels at 

 a rate of at least one-third of a knot in water 

 of a 40-foot depth. 



Commercial sponges grow well in water cur- 

 rents with this rateof flow. In areas, such as at 

 Indian Rocks, a current of 2 knots or more may 

 be responsible for the rapid growth of some 

 sponges and other bottom inhabitants. Wool 

 sponges in this area were not affected greatly 

 except that the conules were longer and the 

 oscules higher, up to 2 inches in height. These 

 sponges had heavy overgrowths of tunicates and 

 algae which distorted their shape, and at times 

 were deformed by the crowding of other sponges 

 on the bar. 



The grass sponges in this strong tide area 

 were growing in conical rather than vase 

 shape, with the central portion completely 

 filled in. This was true also of the same spe- 

 cies of sponges in the Cape Romano area 

 where strong tides were found. These grass 

 sponges were soft in texture and commanded a 

 higher price than other grass sponges on the 

 market, having a texture and use comparable 

 to the finest Mediterranean sponges. 



There is a noticeable change in the appear- 

 ance of wool spongesfrom water of less than 12 

 feet to those sponges from 40 and more feet in 

 depth. Sponges from shallow water have up to 

 twice as many conule tufts per square inch. The 

 oscules of wool sponges from shallow water are 

 as much as 1-1/4 inches wide while those from 

 the deeper water are rarely more than three- 

 quarters of an inch wide and usually less. Only 

 slight differences were found in the actual 

 weight to volume ratio from the different 

 depths, the shallow-water sponges being 

 lighter. There was a noticeable difference 

 in compressibility and strength of fiber; 



37 



