The merits of the thin-layer method of Dolman and Gill to study the oxygen binding of haemocyanin were experimentally tested with haemocyanin obtained from arthropods and molluscs. The results show that, spectrophotometrically, oxyhaemocyanin from both arthropods and molluscs has a prominent absorption peak between 335 and 345 nm. Haemocyanin is more stable in the thin- layer preparation when compared with haemoglobin. At 35 °C a decrease in the initial absorbance value of less than 2% was found after three hours. For haemoglobin the initial value decreases nearly 10% during the same period. For a high-affinity haemocyanin such as Marisa cornuarietis (P⁵⁰ = 1,07 mmHg) the thin-layer method of Dolman and Gill (1978) shows better PO₂ resolution than other methods. The reason for this is that the dilution valve, which is absent in other thin-layer methods, intrinsically measures the resultant PO₂ values at very low tensions more accurately. In this study a step-by-step explanation of the technique is given. The calculations have been explained using real figures and examples. It is hoped that this detailed description will make this technique more readily available for use by respiratory physiologists.
External and internal shell formation in the ramshorn snail Marisa cornuarietis are extremes in a continuum of gradual variation in development
