Vascular Specialization in Fish, but No Evidence for Lymphatics

Blood Vascular System, Endothelial Cells, Lymphatics, Bony Fishes Blood distribution in the systemic circulation of bony fishes is effected by a dualistic construction of the vascula­ ture: A secondary arterial system originates from the well known (primary) arteries by multiple root-like shunt vessels. These secondary arteries and the vessels they supply should no longer be regarded as lymphatics. After an intensive search for unequivocally lymphatic vessels in fish, it ap­ pears doubtful whether there are any at all in this class of vertebrates.