Abstract
Ectoparasitic cookiecutter sharks (Chondrichthyes: Squaliformes: Dalatiidae; Isistius ) share common features for jaw and teeth structure, in particular, robust lower jaws and dignathic heterodonty (upper teeth crowns are more slender and shorter than the broader and longer lower teeth crowns). The jaws and teeth are well suited for feeding by excising a nearly symmetrical oval-flesh bite plug from a variety of prey species including marine mammals, fishes, and squids. There is considerable speculation regarding cookiecutter shark bite dynamics given that natural feeding behavior has not been observed. To elucidate cookiecutter shark bite dynamics, bites were experimentally simulated for the two cookiecutter shark species; the Cookiecutter Shark, Isistius brasiliensis (Quoy JRC, Gaimard, P (1824) Zoologie (3) Imprimerie royale) and the Largetooth Cookiecutter Shark, Isistius plutodus (Garrick JAF, Springer S (1964) Isistius plutodus, a new squaloid shark from the Gulf of Mexico. Copeia 678–682), using three-dimensional printed models of jaws with teeth. Bite simulations were conducted at standardized jaw bite-gape angles and ballistic gelatin was used to approximate prey flesh, from which aspect ratio analysis of bite wound geometrics was used to determine bite wound morphometrics for each species. The simulated bite experiment also was useful for assessing factors that potentially affect cookiecutter shark total length estimates when based on natural bite geometrics. In addition, the mechanics of producing experimental bites provide new insights related to the necessity for cookiecutter sharks to rotate their body to create nearly symmetrical oval bite wounds.