THE MUSCULAR ACTIVITY AND OXYGEN CONSUMPTION OF URECHIS CAUPO

¹ From the Physiological Laboratory of the Hopkins Marine Station, Pacific Grove, Calif

The greater part of the muscular activity of the echiuroid worm Urechis caupo is involved in pumping a current of water through its U-shaped burrow. The magnitude of this current was studied in artificial burrows, food-free water being supplied to the animals. When the animal is not feeding, the current amounts to about eleven cubic centimeters per minute. During feeding periods, the rate of pumping rises to about twenty-nine cubic centimeters per minute. The frequency, duration and course of activity during these feeding periods has been studied. The significance of the stream in relation to provision of oxygen and food is discussed.

The oxygen consumption of the animals in U-tubes amounts to 0.00021 cc. per gram per minute, being comparable to that of related forms. It is independent of the oxygen pressure down to a value of 70 mm. Hg.

The oxygen consumption of the worms when placed in covered jars decreases with falling oxygen pressure throughout the range investigated, 115 to 4 mm. Hg. The reasons for this fall are discussed.