Fast Fish

Both marlins (Istiophorids) and mako sharks (Lamnids), two very large, pelagic fishes, can burst swim at very high speed. Swimming quickly requires a stiff body to minimize the wasteful pushing of water to the sides. The marlin has a bony skeleton and it is stiffened by the simple of expedient of having very few vertebrae and tying those vertebrae together with bony bridges (zygapophyses) and connective tissue. The mako on the other hand has a cartilaginous skeleton and a great many simple, disk-like vertebrae. We have confirmed that sharks stiffen their body by increasing their internal pressure when they swim fast. The thick, inextensible skin must then resist any expansion and would make the body stiffer. Discover Magazine featured a brief article on this research.

Gabby Martinez (Blinks Fellow), Eliot Drucker and I tested this hypothesis at Friday Harbor Labs using spiny dogfish as a model system. Jaquan Horton (Blinks Fellow), Eliot and I then tested whether bony fishes can pressurize their body. They do, but the net pressure does not increase with increasing speed.

This summer (2005) we hope to gather a data set on pressure variation along the body and from the skin to the vertebral column.

Gabriela Martinez, Anna Hof Blinks Fellow, and PhD student from the University of New Hampshire, determining whether sharks pressurize their body as they swim faster.

 

Testing the flexibility of a hammerhead spinal column on a field trip to El Barril, Baja California, Mexico. All sharks have relatively flexible vertebral columns but the hammerhead is exceptionally bendy. See Steve Kajiura's web pages for our hypothesis about hammerheads.

We presented this work as a poster at the 2003 SICB meeting in Toronto.