Immunohistochemical Demonstration of Lymphatic Vessels in Adult Zebrafish

Morphological profiles of lymphatic vessels in adult zebrafish trunk and ovary were studied by immunohistochemistry and electron microscopy. The present immunohistochemistry for Prox1 was successful in demonstrating lymphatic vessels in zebrafish. The zebrafish trunk revealed two types of bilateral longitudinal lymphatic trunks draining lymph centripetally along dorsal aorta and posterior cardinal veins. Large honeycomb lymphatic sinus was further shown around common cardinal veins. In the zebrafish ovary, the lymphatic vessels, comprising endothelial cells only, encompassed arterioles in their lumen. This peculiar structure appeared to be conserved in vertebrates including mammals and might serve for control of blood temperature and tissue homeostasis. The present study is first to delineate lymphatic vessels in adult zebrafish by immunohistochemistry. Our immunohistochemical results showed usefulness of immunostaining for Prox1 not only for demonstration of lymphatic vessels in zebrafish, but also for examination of their function and dynamics in pathophysiological condition.