Abstract
ABSTRACT The erythroblasts of the Teleost Lebistes reticulatus, when visualized with the Unna-Brachet technique, appear at the 2-somite stage of development. The earliest visible erythropoiesis is then located in the ventral part of the border of the blastodisc. Along this border it rapidly extends towards the posterior extremity of the embryo, where it appears continuous with the elements of the ‘Intermediare Zellenmasse’ of Oellacher. The blood-forming rudiment in the embryo itself becomes visible only at the stage of 5 somites, and takes the shape of an inverted Y whose long limb is localized in the midline of the posterior somitic region of the embryo; the two branches of the Y taking their origin in the posterior part of the extra-embryonic tissue on both sides of the terminal node. Blood-circulation becomes apparent at the 15–17-somite stage, and at the surface of the yolk the blood-cells then move towards the venous side of the heart. The closure of the blastopore occurs around the stage of 18 somites, when the blood-circulation is already established. These observations do not correspond with what is found in other Teleosts where the blood-forming rudiment appears to be situated only in the dorsal part of the body. It would now seem possible to relate this extraordinary origin to the situation which prevails in other Vertebrates.
Published Version
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