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Fig. 15 | EvoDevo

Fig. 15

From: Expression of NK cluster genes in the onychophoran Euperipatoides rowelli: implications for the evolution of NK family genes in nephrozoans

Fig. 15

Alternative scenarios on the evolution of pulsatile organs in nephrozoans. Phylogeny modified from Ref. [16]. A Single origin of the heart and expression of NK4 in cardiac tissue in the last common ancestor of Nephrozoa. According to this scenario, multiple independent losses of hearts occurred in numerous spiralian and ecdysozoan taxa. Additionally, expression of NK4 in cardiac tissue was lost in mollusks. B Convergent evolution of hearts in deuterostomes, panarthropods, annelids and mollusks with either a gain of heart in the onychophoran/arthropod lineage or a secondary loss of the heart in tardigrades. According to this scenario, NK4 might have been recruited independently to fulfill regulatory functions during heart development in vertebrates, panarthropods and annelids, but not in mollusks. Abbreviations: B, Bilateria; D, Deuterostomia; N, Nephrozoa; P, Protostomia

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