Ciliary Activity and Oxygen Uptake in Branchiostoma Lanceolatum (Pallas)

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Abstract
The rate of oxygen uptake by single specimens of Branchiostoma lanceolatum has been shown to vary considerably. Some animals in sealed vessels at 15 ° C. were able to utilize the oxygen linearly down to less than 20% of air saturation. Others ceased to absorb oxygen at high saturations while yet others displayed two different rates in a sequence starting initially with a high rate. There are three possible rates of oxygen utilization, as well as a zero rate, for an animal at any temperature between 10 and 19 ° C. Animals in gravel exhibit only two rates at lower temperatures. The slowest rate varies exponentially with temperature but the two faster rates show a rapid increase between 10 and 15 ° C. with little change outside this temperature range. The effect of size and temperature on the increased oxygen uptake during the faster rates of respiration are discussed. It is suggested that ciliary activity of the pharynx could be associated with the extra oxygen utilization. It has been found that there are three inhalant stream velocities, a fast, a slow and a zero rate with no intermediate rates. Study of the isolated portions of the pharyngeal wall confirm that the fast inhalant current is set by the activity of all the cilia to give a feeding stream. The slow stream is set up by the lateral cilia, which continue to beat when the frontal cilia and most of the lateral cilia have been inhibited by lowered oxygen concentrations. The lateral cilia have been shown to be under nervous control and to be inhibited by pressure on the pharyngeal bars. This mechanism depends on the presence of a connexion between the pharyngeal bars and the endostyle.

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