Preliminary studies on haemoglobin and other proteins of the Pogonophora

Starch gel electrophoresis of extracts ofSiboglinum atlanticumshowed that all five individuals tested have two acidic haemoglobin components and a strong α-naphthyl acetate esterase. There was individual variation in the position of the esterase. Low levels of amylase activity were found in the extracts but no trace of dehydrogenases for such important substrates as glucose-6-phosphate, lactate, malate, and glutamate could be revealed by standard histochemical methods as applied to zone electrophoresis. The high level of haemoglobin and the protein peculiarities of the Pogonophora are discussed in relation to experiments on respiration. It is concluded thatSiboglinumhaemoglobin functions at very low oxygen partial pressures and that the high level of haemoglobin dissolved in the blood plasma of pogonophores does not reflect a high level of oxygen consumption or activity. The meagre biochemical data at present available on the Pogonophora do not favour relationship of this phylum to the echinodtrm-chordate line any more than to the annelids or other invertebrate phyla.INTRODUCTIONLargely as a result of studies by A. V. Ivanov, the phylum Pogonophora has become recognized by zoologists in the past decade (reviewed by Hyman, 1959, esp. pp. 208–27; Ivanov, 1963; E. C. Southward, 1963). Pogonophores are small, extremely vermiform animals, living in tubes partly im-bedded in mud or muddy sand; while in some areas they are sufficiently abundant to dominate the benthic fauna, their occurrence at great depths has made living pogonophores very difficult to obtain.Two especially interesting problems associated with this newly recognized phylum are:(a)Pogonophora are the only group of free-living Metazoa without a gut at any stage in their development, and thus, the method of feeding and type of metabolism has been the subject of considerable speculation;(b)Pogonophora possess a few characteristics—e.g. a ventral heart and dorsal nerve cord—suggestive of the echinoderm-chordate line of evolution.