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Regeneration of the proboscis of muricid gastropods after amputation, with emphasis on the radula and cartilages.

Boring of prey shells by muricid gastropods involves the close interaction of the proboscis, propodium, and the accessory boring organ (ABO) in a predictable cycle which repeats itself continuously throughout the process of boring of each borehole. Although the radula serves only a minor part in shaping the borehole, it appears that both the radula and the ABO are necessary to effect normal penetration ( Carriker and Van Zandt, 1972) . Whether this is so could be tested by inactivation of one and then the other organ in different individuals and noting the effect on penetration. The first objective of the present study was to examine the effect of removal of the proboscis on boring. In 1957 an adult Urosalpinx cinerea in our laboratory caught its proboscis be tween the glass and shell of an oyster model (Carriker and Van Zandt, 1972) , and after tugging for some time to free itself, tore away the proboscis leaving the distal third wedged in the model. The snail recovered and resumed boring of prey in 20 days. The previous year Demoran and Gunter ( 1956) experimentally ampu tated the distal portion of the proboscis of several thaisid boring snails, Thais haemastoma, and reported that these gastropods regenerated the proboscis within three weeks provided the organ had been cut off cleanly. From time to time the senior author has dissected large adult Urosal/inx cinerea collected in the field in which the anterior portion of the proboscis, though abnormally small, externally appeared morphologically normal. The small size of the proboscis tip indicated that these snails had accidently lost and regenerated the proboscis. These several ob servations suggest that regeneration of the complex buccal mass in Urosalpinx cinerea (Carriker, 1943) and other predatory marine gastropods may occur nor mally in nature. The second objective of this investigation was thus to determine how commonly and at what rate regeneration occurs in the laboratory after experi mental proboscisectomy. A preliminary summary of the results of these studies was published by Carriker (1959, 1961). The radula, being a relatively hard struc ture (Carriker and Van Zandt, 1972) provides a readily measurable parameter for quantitative determination of regeneration. During the past several decades regeneration of cartilages has been investigated almost exclusively in vertebrate animals. Recently, however, following a long period of neglect, invertebrate cartilages again came under serious study (Person and Philpott, 1969; Mathews, 1968). As part of a survey of the nature and prop 317