Whale shark filter feeding: morphology, mechanism and consumption. 

Motta, P., Davis, R., Hueter, R., Maslanka, M., Mulvany, S., Habegger, M.L., Mara, K., and J. Gardiner.

 Whale sharks R. typus, utilize either pulsatile suction filter feeding, or continuous ram filter feeding. Our lab is undertaking a study of the feeding behavior and functional morphology of the feeding apparatus of these gentle giants. Working in conjunction with scientists from Mote Marine Laboratory and the Georgia Aquarium we film these sharks off Holbox, Mexico. The whale sharks swim through dense plankton patches filtering out plankton with their highly modified gill filtering pads. To try and quantify filtering rates we videotape the feeding sharks with high speed video. Divers also enter the water ahead of the shark and film the feeding shark as it passes the diver. In this manner we can analyze the video to count the pulsatile opening and closing rate, and by tracking particles we can measure the flow rate of water into the mouth. Swimming speed of the feeding sharks is also determined by GPS. Samples of the plankton or food they are feeding are also simultaneously taken in order to identify the food and its density inside and outside of plankton patches. Ongoing research is investigating the unique filtering apparatus, a series of porous pads that totally occlude the pharynx.

To see an article about our research in the Washington Post, click here.

Abstract – 2007 American Elasmobranch Society meeting, St. Louis, MO July 11-16.

Whale shark filter feeding: morphology, mechanism and consumption. 

Motta, P., Davis, R., Hueter, R., Maslanka, M., and S. Mulvany.

The world’s largest fish, the whale shark Rhincodon typus, utilizes ram and suction filter feeding to engulf planktonic and small pelagic prey. The ram filtering feeding behavior was investigated in situ at feeding aggregations of whale sharks off Isla Holbox, Quintana Roo, Mexico. Sharks were feeding on dense aggregations (4.3 g/m3) of plankton, primarily composed of calanoid and cyclopoid copepods. Filter rates based on mouth morphometrics and swimming speeds were calculated, and together with plankton tows gave an approximate estimate of biomass consumption of 2.2kg/h. To investigate the mechanics of feeding, the filtering apparatus was dissected on a 7 m TL specimen. Small, denticulated teeth ring the jaw, and a double buccal valve posterior to the jaw reduces water backflow out of the mouth. A novel filtering apparatus consists of a series of twenty filtering pads that lie dorsally and ventrally on either side of the branchial apparatus at an angle to the incoming water. These pads, which completely occlude the branchial arches, have pores of varying diameter. A mechanism of crossflow filtration whereby particles are entrained posterior to the pads is proposed. After passing through the pads an elaborate system of channels directs water within the branchial pad, through what appear to be collimator vents, and over the gill lamellae before exiting the pharyngeal slits.