Haemocyanin. Coloured transmission electron micro- graph (TEM) of molecules of haemocyanin, a respiratory protein and pigment found in molluscs and arthropods. Like haemoglobin in mammals, haemocyanin is an oxygen carrying molecule. Each molecule is barrel-shaped appearing rounded end-on but oblong with transverse striations when seen from the side. Here, the haemocyanin molecules are from a marine whelk Burnupena cincta. They are a copper- containing protein (non-porphyrin) that occurs in solution in mollusc haemolymph blood". It is blue when oxygenated, colourless when de- oxygenated. Magnification: unknown."