DEMINERALIZATION MECHANISM OF BORING GASTROPODS 57 



The boring function may be reviewed briefly as follows. Drilling 

 gastropods readily locate prey in their immediate surroundings, ap- 

 pearing to orient to external metabolites emitted by them (Blake, 

 1960); the manner of identification of the metabolite signal, and of 

 the prey after the snail has mounted it, is not known. Once contact 

 has been made with prey and a drilling site on it has been selected, 

 the snail rasps this free of incrustations, periostracum, and loose 

 shell material with the radula; then it brings the ABO immediately 

 over the drilling site, and extends the organ into the shallow con- 

 cavity. The foot during this time adheres strongly to the prey, and 

 completely hides and protects the ABO. While the ABO is everted 

 in the concavity, there is no noticeable external movement of the 

 snail, and its pedal surface, firmly applied over a copious film of 

 mucus to the intact surrounding shell, appears to eftect a water- 

 tight connection. After an interval of a few minutes in Naticidae, 

 and as long as an hour in Muricidae, the ABO is gradually with- 

 drawn, and the snail explores the surface of the excavation and close 

 surroundings with the proboscis tip and propodium. Rasping within 

 the region affected by the ABO is then resumed and continues for 

 a few minutes; the proboscis is held snugly in a groove fomied by 

 infolding of the propodial folds. Radular teeth are rather ineffectual 

 in removing untreated shell, as demonstrated by the fact that flakes 

 of shell are not removed at the close of the rasping period. Alterna- 

 tion of periods of rasping and chemical action continues until a per- 

 foration is completed, and the snail then feeds on the flesh of the 

 prey through the hole it has drilled. By removal of the ABO and 

 the radula in different individual muricids, Carriker (1959) demon- 

 strated that penetration involves obligatory alternate use of the 

 radula and of the demineralization organ. When functioning, the 

 ABO is swelled by hemostatic pressure and is extended to the deep- 

 est extremities of the hole, maintaining the distal secretory epithe- 

 lium in close contact with the shell substance at the bottom of the 

 hole. 



Perforations made by boring gastropods are characteristically 

 smooth and circular, penetrate the shell at right angles to the sur- 

 face, and may decrease noticeably in diameter at the inner end. 

 The outer parts of naticid borings are broadly beveled, converging 



