Nurse sharks Ginglymostoma cirratum, are obligate suction feeders. The functional morphology of the feeding apparatus is investigated via high-speed videography and electromyography (EMG). Using external and internal pressure catheters we are also measuring buccal pressure during feeding events on captive and wild nurse sharks.  Pressure drop is extremely rapid and can reach as low as one atmosphere, with our maximum recorded sub-ambient pressure being -109 kPa. There is no relationship between shark size and maximum sub-ambient pressure, but the rate of pressure drop is directly related to the maximum sub-ambient pressure. The more rapid buccal expansion and hence pressure drop, the greater the buccal pressure. Suction pressure can be so large that prey are dismembered during capture. Because pressure drops so rapidly in front of the mouth, suction capture by this shark is a near field phenomenon, being restricted to distances less than 3 cm. It is hypothesized that this species therefore utilizes primary ambushing or stalking to closely approach its prey prior to suction, often placing its head and mouth inside crevices before its explosive suction.

Representative suction pressure traces for the nurse shark.

Nurse sharks are abundant, demersal sharks found throughout the year in shallow waters of tropical Florida and the Caribbean.  Nurse sharks feed on or near the bottom and in rocky and reef areas on fishes, mollusks and crustaceans (Castro 2000) and can lie motionless on the bottom for extended periods of time.  They are suction feeders (Motta et al. 2002) with a well-developed olfactory apparatus.  It was once believed that this species could locate food using olfaction alone, through chemical gradient searching (Hodgson and Mathewson, 1971; Mathewson and Hodgson, 1972) however Kleerekoper et al. (1975) found that nurse sharks need flowing water to provide a directional vector.  I am examining the striking preferences of intact animals as they are presented with spatially separate sources of olfactory, mechanical and electrical stimuli, as well as the effect of sensory lesions on the kinematics of the capture of live prey.