© 2001 by The Society for Integrative and Comparative Biology
Costs and Benefits of Opisthobranch Swimming and Neurobehavioral Mechanisms1
1 University of Washington, Friday Harbor Laboratories, 620 University Road, Friday Harbor, Washington 98250
After opisthobranch molluscs dislodge from the substrate during onset of swimming, the ensuing flexion or undulatory motions are usually not well oriented with respect to predators, prey or suitable substrate. Swimming motions are effective in launching animals off the substrate and elevating them into the water column where they are primarily transported passively by ambient waves and tidal currents. Both active swimming and passive transport on ambient currents may provide escape from predators, search for food and mates, and dispersal to new and potentially adaptive locations. However, loss of contact with the substrate and launching into the water column may also bring a high cost in terms of exposure to diverse risks. I illustrate several forms of opisthobranch swimming and describe their mechanisms and roles. In addition, adaptations of some opisthobranchs to reduce the risks of exposure to predators during swimming are suggested. These adaptations include small size, transparency or inconspicuous color to reduce predation while swimming, and neurobehavioral mechanisms of rheotaxis and geomagnetic sensitivity.