Distribution of Iron‐Containing Granules in Lampreys, with Particular Reference to the Southern Hemisphere Species Geotria australis Gray

Perl's Prussian blue and bathophenanthroline have been used to investigate the sites where iron‐containing granules are found within representatives of each of the three extant families of lampreys. Amongst the larvae, granules were present in the columnar cells of the posterior intestine in small amounts in some but not all northern hemisphere species (Petromyzonidae), and in moderate and very large amounts in the southern hemisphere families Geotriidae and Mordaciidae respectively. Granules were only found in large numbers elsewhere in the body of larvae of the Geotriidae, in which they were predominant in the adipose tissue of the nephric fold and fat column. It is suggested that these large iron deposits reflect the intake of an unusually large amount of iron, a feature which in turn could be related to the relatively high plasma iron levels and haemotocrit found in larvae of the Geotriidae. During metamorphosis, iron deposits accumulate in the liver of all species as haemoglobin is broken down.