15.0 

 TEMPERATURE °C. 



25.0 



Figure 1. — Feeding rates of starfish on oysters at constant temperatures. (Points are based on combined data 



of replicates at each temperature level — see table 1.) 



FEEDING RATES AT CONSTANT 

 TEMPERATURES 



METHODS 



For the feeding experiments with starfish held 

 at constant temperatures, wooden frames, con- 

 structed to hold a bank of four enamel trays (C 

 cm. by 43 cm. by 50.5 cm.), were arranged on lab- 

 oratoi-y tables. Each bank was supj^lied witli a 

 separate, continuous flow of sea water. By mixing 

 cold and heated sea water in glass cylinders just 

 above the frames, we maintained the water in the 

 trays within ±1° C. of the temperature desired. 



I belie\e the range of salinity of the water 

 (26.8%„-28.2%o), which corresponds with that of 

 the natural habitat of starfish near Milford, Conn., 

 did not significantly influence the feeding rates 

 during the experiment. 



At each temperature four or eight trays were 

 used, each containing 3 adult starfish and 40 

 oysters. The starfish weighed between 39 and 41 

 g. (starfish were drained individually for 30 sec- 

 onds before weigliing) and averaged &4 mm. 

 (range 53-75 mm.) from tip of two arms nearest 

 the madreporite to the madreporite. The heights 



of the oysters averaged about 50 mm. (range 34-- 

 80 mm.). Some oysters were in clusters, and others 

 were individuals. To ensure an ample food supply 

 for the starfish, shells of consumed oysters were 

 removed nearly every day and replaced by live 

 oysters. 



A fresh group of starfisli was obtained in Jjoug 

 Island Sound off Milford for each repetition of a 

 28-day test at a series of temperatures. These 

 animals were placed in large containers of water 

 at the same temperatures as when they were col- 

 lected. As the water temperature gradually rose 

 indoors to the point desired, starfish were placed 

 in the experimental feeding trays maintained at 

 this temperature. Oysters, acclimated to the ex- 

 perimental temperature in the same way, were 

 placed in trays with the starfish 1 or 2 days latei-. 

 Only one starfish died in pans in whicli water tcin 

 peratures ranged from 5° to 22.5° C. At 25° C, 

 however, 14 of 72 starfish died during tlie ex- 

 periments and one additional starfish lost an arm. 



RESULTS 



Feeding rates are expressed as the number of 

 oysters consumed per starfish during the 28 days 



68 



U.S. FISH AND WILDLIFE SERVICE 



