The swimming response of the Sacconereis stage of Autolytus varius to changes in hydrostatic pressure

Graduation date: 1969The syllid polychaete Autolytus varius reproduces in the spring\ud and early summer in Yaquina Bay, Oregon, The fertilized female\ud epitokes, or Sacconereis, carry the developing eggs and larvae in a\ud ventral sac until the larvae are ready to be released; incubation\ud lasts 14 to 18 days in the laboratory, The effects of a small increase\ud in hydrostatic pressure on the activity of Sacconereis were tested,\ud When placed in a pressure vessel, these epitokes responded to increases\ud of 0.39 Bar by orienting dorsally and swimming upward,\ud and by increasing their swimming rate, Peak activity occurred in\ud the first minute after a pressure stimulus. Following this, there\ud was a period of accommodation until the epitokes returned close to\ud their normal level of activity; the period of accomodation lasted\ud around 11 minutes, When the pressure was released, the worms\ud either slowed their swimming rate, or they coiled and sank rapidly\ud to the bottom of the vessel. Decerebrate Sacconereis of A. varius\ud did not respond to pressure stimuli. The Sacconereis of A. magnus\ud and A. prismaticus, and the Polybostrichus of A. prismaticus\ud demonstrated swimming responses similar to A. varius Sacconereis.\ud Three other species of polychaetes did not respond to pressure\ud changes. The hydrostatic pressure response is possibly an adaptation\ud of a planktonic stage of a normally benthic animal