GAS-TRANSPORT IN THE HEMOLYMPH OF ARACHNIDS .1. OXYGEN-TRANSPORT AND THE PHYSIOLOGICAL-ROLE OF HEMOCYANIN

Oxygen equilibrium curves and the relationships between the partial pr essure of CO2 and pH were determined for the haemolymph of the arachni ds Eurypelma californicum, Pandinus imperator and Cupiennius salei. A new type of experimental apparatus was constructed, tested and used to make these measurements on small undiluted cell-free haemolymph sampl es. Most of its components were made in our workshop and were inexpens ive. The apparatus proved to be very reliable as demonstrated by contr ol (oxygen concentration) experiments. In previous reports on O-2 equi librium curves of E. californicum haemocyanin, Tris-HCl buffer was use d to set the pH, whereas in our experiments, pH was adjusted by alteri ng the partial pressure of CO2. The O-2 concentration measurements dem onstrate an increase in oxygen affinity of E. californicum haemocyanin when using Tris-HCl buffer. The position and shape of the O-2 equilib rium curves of E. californicum and P. imperator haemocyanin show a dis tinct dependency on pH. Oxygen affinity is lower in E. californicum an d cooperativity changes with pH in E. californicum, but not in P. impe rator. Oxygen transport in the haemolymph of E. californicum during re st, activity and recovery was calculated on the basis of the O-2 equil ibrium curves of undiluted haemolymph. Apart from oxygen transport, th ere are indications that haemocyanin is also involved in other physiol ogical processes. For example, it may function as a storage protein.