In fish blood vessels can develop from lymphatics

During development, the cardiovascular system is already fully functional when the lymphatics system forms as a merger of outgrowths of the cardiovascular system (the lymphatic sacs) and differentiated precursor cells. Despite all controversies, one thing was always certain: lymphatics develop from blood vessels, but blood vessels never from lymphatics. But this certainty has just been demolished by Das et al., who found that in zebrafish blood vessels can develop from lymphatics...

That lymphatics can form from blood vessels is textbook knowledge, but at least for zebrafish, the textbooks need to be re-written: A sizable fraction of the cardiovascular system in zebrafish seems to form from lymphatics. Notably, the blood vessels of the so-called secondary vascular system (SVS) appear to form by transdifferentiation from lymphatics. This ground-breaking research was done by Das et al. from the Yaniv lab at the Weizmann Institute of Science ( Although the SVS is the central topic of the publication, the SVS is mentioned only twice in some subordinate clauses. Therefore Kari Alitalo and I thought it would be a good idea to spell out explicitly what this paper describes: the embryonic development of the SVS. Have look at the Das et al. Nature paper and Kari's and my Nature Cardiovascular Research piece.