title: Ultrastructure and changes during metamorphosis of the lympho-hemopoietic tissue of the larval anadromous sea lamprey Petromyzon marinus.
abstract: The ultrastructure of the lympho-hemopoietic tissue of the typhlosole and opisthonephros of larval Petromyzon marinus was studied throughout the life cycle. In both locations, lympho-hemopoietic tissue houses a connective tissue stroma and is irrigated by a system of enlarged blood sinuses lined by a continuous endothelium. The typhlosolar and opisthonephric lympho-hemopoietic tissue consists of mature and developing blood cells belonging to erythroid, lymphoid, monocytic and granulocytic lineages. During metamorphosis there is a total degeneration of the larval opisthonephros and a full transformation of the digestive apparatus. As a consequence of these modifications the typhlosole and the opisthonephros lose their hemopoietic capacity. These changes are discussed in view of the role played in them by the so-called "hemopoietic inductive microenvironments", principally the stroma supporting apparatus and vascularization pattern.
mesh_terms: D000818:Animals; D005399:Fishes / Q000254:growth & development*; D006413:Hematopoietic System / Q000254:growth & development* / Q000648:ultrastructure; D007798:Lampreys / Q000033:anatomy & histology / Q000254:growth & development*; D008221:Lymphoid Tissue / Q000254:growth & development* / Q000648:ultrastructure; D008675:Metamorphosis, Biological; D008854:Microscopy, Electron