A Proposal for the Adaptive Significance of the Development of the Lamprey Fat Column

Abstract

Lampreys differ from the other extant agnathan group, the hagfishes, in possessing a fat column above the nerve cord. It is suggested that this region of fat is just one of many sites of lipid storage that have been developed to provide energy reserves for the lengthy non-trophic periods found during the life cycle of lampreys. The incorporation of this fat within an extension of the nerve cord sheath suggests that it could act as a protective dorsal cushion for the nerve cord, which would otherwise be more exposed due to the absence of complete vertebral arches. The development of the fat column as the principal blood cell forming structure in the adult can apparently be related to certain changes that take place during metamorphosis, particularly in the circulatory system.