DIFFERENCES IN THE TOTAL LIPID AND LIPID CLASS COMPOSITION OF LARVAE AND METAMORPHOSING SEA LAMPREYS, PETROMYZON-MARINUS

This study compared the alterations in total lipid and lipid class com position of kidney, liver, and intestine from sea lamprey, Petromyzon marinus, during their nontrophic metamorphosis with these parameters i n unmetamorphosed larvae. Total lipid in kidney and liver initially wa s higher by 104 and 66%, respectively, in the earliest metamorphic sta ge (3) examined compared to larvae and then decreased by 73 and 37%, r espectively, from stage 3 to stage 7. Total lipid in intestine, on the other hand, was 53% lower at stage 3 compared to larvae and then sign ificantly increased by 260% from stage 3 to stage 7. Large amounts of triacylglycerol (TG) in kidney and liver implicate these organs as lip id depots; much of the change in total lipid content of kidney and liv er could be explained by alterations in TG, although significant varia tions in other lipid classes (e.g., phospholipid, cholesterol) also we re noted. These results suggest that lamprey metamorphosis may proceed in two metabolic phases in a tissue-specific manner and that lipid de pletion results from specific catabolism of stored TG reserves.