Ontogeny of the sea bass spleen (Dicentrarchus labrax): A light and electron microscopic study.

Abstract

AbstractThe splenic rudiment in sea bass (Dicentrarchus labrax) appears 18 days after hatching in the right side of the body, close to the dorsal wall of the anterior part of the intestine. It acquires its final localization after about 2 months in a middle‐ventral position between the cecal part of the stomach and the first intestinal loop. The haemopoietic activity of this spleen during organogenesis varies with age. During the first 40 days only erythropoietic activity is shown, after which thrombopoiesis begins and the first lymphocytes appear. At the time that the amorphous extracellular matrix increases, some reticular, cells of the stroma undergo an active lipid synthesis, which ceases when the larvae are about 2 months old. All the above coincides with a decrease in erythropoiesis and total vascular development, although the ellipsoids and sinusoids do not present their final structure until later stages. These structural variations create microenvironmental conditions which favor modifications in the activity of the spleen. This relation between microenvironment and changes in haematopoietic organ function has also been described in mammals and birds (Metcalf and Moore [1971] Frontiers of Biology. Amsterdam: North Holland; Quesada et al. [1985] J. Submicrosc. Cytol. 17:537–540; Yassine et al. [1989] Cell Diff. Dev. 27:29–45). © 1994 Wiley‐Liss, Inc.