Feeding behavior 



According to Pope (1910-11) it is not uncommon for two Urosalpinx to ex- 

 tend their proboscides through a drill perforation and thus feed side by side . 

 After the valves of an oyster gape open as a result of drill predation, other drills, 

 attracted by the food, crawl within the opened oyster and literally bury themselves 

 in the meat as they feed. The drill primarily responsible for the killing invariably 

 continues to feed through the perforation . In addition to Urosalpinx, crabs and 

 fish are also attracted to the wounded oyster, and consume it before the drills are 

 able to finish it. 



In the laboratory drills have been observed to feed continuously on 

 oyster meat for periods rangmg from 12 to 20 hours (Carriker, 1943). Pope 

 (1910-11) observed that an isolated drill in a few days drilled and consumed five 

 young oysters not exceeding 1.9 cm. in length. Galtsoff et al , (1937) write that 

 in their laboratory a single drill penetrated and ate an oyster 5 cm . long; and 

 another devoured about . 4 cubic inch of oyster meat in 24 hours . 



Effect of drilling on oysters 



Federigfai (1931c) performed experiments in the laboratory v/hich suggest 



that Urosalpinx while perforating an oyster secretes a toxic substance which 

 kills the bivalve . Oysters penetrated to the eurface of the mantle lying against 

 the shell recovered. But those in which the adductor muscle, the pericardial 

 cavity, or the visceral mass were penetrated deeply opened immediately and did 

 not recover. Oysters perforated in less vulnerable areas along the periphery, 

 although they did not gape for several days, also died. In striking contrast 

 oysters' similarly perforated with a machinists twist drill continued to live in- 

 definately. No confirmation of these provocative observations has ever been 

 reported. In Federighi's experiments it is of some significance whether the mach- 

 inists twist drill injured the oyster tissues to the same degree as the rasping of 

 the Urosalpinx radula This was not reported. 



Rate of destruction of prey 



Numerous records attest the destructiveness of U. cinerea . The avail- 

 able quantitative data on the rate of destruction of oysters has been tabulated 

 in Tables 8 and 9. 



Pope (1910-11) stresses the fact that the drill is destructive as soon as 

 it hatches from the egg case, and owing to the diminutive size of both newly 

 hatched drills and recently set oyster spat the real extent of the mortality of very 

 young oysters is generally unknown and unrecognized. Stauber (1943) in Delaware 



54 



