rapidly until the temperature exceeds 84° F. 

 With a further rise of 2 or 3 degrees in 

 temperature the number of sponges producing 

 larvae falls from 70 percent or more to about 

 25 percent. Even with a drop in temperature 

 the percentage of sponges producing larvae 

 continues unchanged until the temperature is 

 below 73° F. at which time larval production 

 ceases. 



In the British Honduras area the cycle is 

 more complex. Here the monthly mean water 

 temperature never falls much below 79° F. In 

 the late winter and early spring when the tem- 

 perature is rising, larval production also in- 

 creases but again, as the temperature goes 

 above 84° F., the number of sponges producing 

 larvae declines and finally tapers off to about 

 7 percent. As the temperature falls below 

 84° F., larval production increases but never 

 more than 50 percent of the sponges are gravid. 

 When the temperature again begins to rise in 

 the next yearly temperature cycle, it is accom- 

 panied by a rapid increase in larval production. 



The production peaks in the Bahamas follow 

 the same pattern, as in British Honduras. The 

 first peak, in April, May, and June, occurs 

 while the temperature is rising. There is a 

 decline when the temperature is above 84° F., 

 with a second peak in larval production in 

 November and December when the temperature 

 again falls below 84° F. This second peak ap- 

 pears to be very slow in starting, and part of 

 the peak actually occurs while the temperature 

 is below 73° F. The temperature data for the 

 Bahamas were obtained from a study by C.L. 

 Smith (1940) and were early morning tempera- 

 tures. 



It would be expected that there would be 

 optimum temperatures which would stimulate 

 the production and release of the sexual prod- 

 ucts (in this case the sperm) and also increase 

 the receptiveness of the eggs for fertilization. 

 Shortly after the sperm are released, the egg- 

 producing sponges would have enlarging em- 

 bryos which would be readily visible to the 

 naked eye. Minimum temperature for the re- 

 lease of the sperm appears to be about 73° F. 

 Above 80° F. there apparently is a much 

 stronger stimulus for this release and a much 

 larger percentage of sponges are producing 



larvae. Above 84° F. either the sperm are not 

 released from the male sponge (or become im- 

 potent), or the eggs become unreceptlve, for 

 larval production ceases. There seems to be no 

 ready explanation why larval production re- 

 mains at a very low level after the tempera- 

 ture declines below 84° F, The data from 

 British Honduras and the Bahamas indicate 

 that a long period of time is required by the 

 sponges to recover their ability to reproduce 

 in quantity while temperature is declining. In 

 the Cedar Keys area the temperature declines 

 so rapidly that before this recovery can take 

 place the temperature drops below 73° F. and 

 larval production ceases. 



The longer reproductive period of the 

 sponges in British Honduras results in much 

 greater egg production than in the upper Gulf 

 area even though the peak of productivity is 

 higher in the Cedar Keys area than in British 

 Honduras. Total larval production in the Cedar 

 Keys area is only about 63 percent of that in 

 British Honduras (fig. 4). When the size at 

 maturation is taken into account, this dis- 

 crepancy may be somewhat increased. Sponges 

 as small as 2 inches in diameter will produce 

 eggs in the warmer waters of British Honduras 

 (F.G. Walton Smith, personal communication), 

 while in the upper Gulf eggs are not normally 

 produced by sponges until they are between 

 5 and 5-1/2 inches in diameter. Thus, if the 

 percentage of sponges producing eggs and 

 larvae in British Honduras is estimated, al- 

 most all the sponges would be potential egg 

 producers. In the upper Gulf, on the other 

 hand, only sponges above 5 inches in diameter 

 have been used to obtain the data; and if all 

 sizes of sponges were considered, the actual 

 percentages of egg-producing sponges would 

 be reduced to about one-third of that indicated 

 in figure 4. 



Temperature and Size at 

 Maturation 



In the Gulf north of Tampa Bay (area D) 

 the minimum diameter of wool sponges pro- 

 ducing larvae was 5 inches. North of Cedar 

 Keys (areas A and B) the minimum diameter 

 for mature sponges, generally speaking, was 

 5-1/2 inches. Only four or five sponges (out 



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