JONES; PROBABLE CAUSE OF CRATER WOUNDS 



Figure 11. — An excised crescentic wound superimposed 

 over a diagram of a skipjack tuna to indicate that the 

 wound was made from a frontal attack, central Pacific. 



position, that is, the shark and its prey were 

 going in opposite directions when the wound was 

 inflicted (Figure 11). Such crescentic wounds, 

 as previously pointed out, are apparently the re- 

 sult of circumstances which do not allow the 

 shark to complete the scooping out process. Be- 

 sides providing support for the suggestion that 

 the teleost makes the initial approach, the evi- 

 dence of frontal attacks may explain the occur- 

 rence of wounds in which the plug of flesh is 

 still attached to the bottom of the wound by a 

 peduncle. Such wounds are common on ceta- 

 ceans (Mackintosh and Wheeler, 1929; van 

 Utrecht, 1959) . In a frontal attack, the drag of 

 water on the shark's body would cause it to ro- 

 tate, in the manner of the hand of a clock, around 

 the point of attachment until the shark was ori- 

 ented in the same direction as its prey. This 

 movement would cause the mandibular teeth to 

 act in the manner of a melon-ball cutter and, if 

 penetration was adequate, the crater wound 

 would be completed. 



To explore this possibility, I employed a nec- 

 tarine (Persicum sp.) from the ship's galley 

 since no large, dead fish was available at the mo- 

 ment. I pushed the teeth of a fresh, dead Isisthis 

 into the fruit and then rotated the body around 

 that point. The result (Figure 4) was a neat, 

 round, crater "wound" and the hemispheroidal 

 "plug" in the shark's mouth with the small, 

 hooked upper teeth securing it. If tooth penetra- 

 tion had been inadequate during such a sequence, 

 the integument would be cut completely around 

 but the plug would remain attached by a central 

 peduncle. Necrosis of the plug would probably 



follow, resulting in conditions described by 

 Mackintosh and Wheeler (1929). They present- 

 ed a hypothetical sequence beginning with a 

 crescentic wound which developed, by gradual 

 erosion of the flesh, to the open pit stage. The 

 "flabby" pedunculate plug, they believed, was a 

 stage in the healing process and was sloughed 

 off near the completion of healing. 



They pointed out that the most obvious cause 

 of crescentic and open pit wounds was the bite 

 of some fish, but no fish known to them possessed 

 teeth or a mouth structure which would produce 

 such wounds. They, therefore, returned to the 

 assumption that the wounds were a result of 

 microbial infections. 



Except in the cases of attacks on squids when 

 the prey is killed, it appears that Isistiiis, in bit- 

 ing pieces out of living cetaceans and fishes, 

 qualifies as a temporary parasite in the same 

 sense that a mosquito does. 



ACKNOWLEDGMENTS 



I want to acknowledge the contributions of 

 many persons who provided unpublished rec- 

 ords, specimens of wounds and scars, photo- 

 graphs, as well as ideas and encouragement 

 during the preparation of this manuscript. My 

 special thanks are extended to John D. Fowler, 

 Jr., NMFS, HAFRC, who initiated the important 

 experiments at sea. 



LITERATURE CITED 



Bane, G. W. 



1969. Parasites of the yellowfin tuna, Thunnus 

 albacares, in the Atlantic Ocean. Wasmann J. 

 Biol. 27: 163-175. 



COLLETT, R. 



1886. On the external characters of Rudolphi's 

 rorqual (Balaenoptcra borealis). J. Zool. (Lon- 

 don), p. 24.3-265. 

 Gakrick, J. A. F., AND S. Springer. 



1964. Isistius plutodus, a new squaloid shark from 

 the Gulf of Mexico. Copeia 1964: 678-682. 

 GlIITART M., D. 



1964. Biologia pesquera del Emperador o Fez de 

 Espada, Xiphias gladius Linnaeus (Teleostomi: 

 Xiphiidae) en las aguas de Cuba. [In Spanish, 

 English synopsis.] Poeyana, Ser. B 1, 37 p. 



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