PHYSIOLOGICAL OBSERVATIONS ON WATER LOSS AND OXYGEN CONSUMPTION IN PERIPATUS

¹ Biological Laboratories, Harvard University, Cambridge, Massachusetts

The Onychophora represent a morphological transition between the annelids and the arthropods. They also represent a physiological transition between the aquatic and the terrestrial environment. In the latter transition the most important adaptations are those involving the functions of water conservation and respiration.

The ability of Peripatus to conserve water has been compared to that of comparable annelids and arthropods. Peripatus is shown to be intermediate to those two groups in this function, losing twice as much water as the centiped, but only one-half as much as the earthworm. This corresponds to its taxonomic and ecological positions.

The "resting" rate of oxygen consumption has also been compared to other animals. The rate in Peripatus is comparable to that in the arthropods and larger than that in the earthworm.

It is suggested that the unique papilla-covered body surface may represent an adaptation for underwater respiration to meet the environmental restriction imposed by the inadequate regulation of water loss.