Evo-Devo Lessons Learned from Hemichordates

  • Kuni TagawaEmail author
Living reference work entry


Hemichordates are exclusively marine animals related to vertebrate chordates, like ourselves, and to non-vertebrate chordates, such as lancelets and ascidians; therefore, they are useful to understand our ancestral state. Hemichordates are also associated with the radially symmetrical echinoderms, organisms such as sea stars and sea urchins, because of similarities in embryogenesis and larval form. Hemichordate larvae are believed to resemble the hypothetical dipleurula larva, which is thought to have been a crucial stage in metazoan evolution. Hemichordates include about 130 described species and are divided into two classes: the free-living Enteropneusta and the sessile Pterobranchia. Enteropneusts are commonly called giboshi mushi in Japanese and acorn worms in English, since the enteropneust proboscis resembles a traditional ornament on the tops of posts or balustrades of bridges, shrines or temples, and acorns. Pterobranchs are small animals that form colonies of clones connected via stalks. This chapter reviews recent studies on hemichordates, focusing on phylogeny, paleontology, molecular developmental biology, and genomics, to review what we have learned about animal evolution and development from these obscure organisms.


Hemichordates Acorn worm Animal evolution Deuterostome Direct and indirect development 



I would like to thank the editor, Dr. Ehab Abouheif, for inviting me to write this chapter. I also would like to express my gratitude to the outstanding investigators in the hemichordate research field, who have always stimulated me in both positive and negative ways. I wish to express my sincere thanks to Springer Nature and the Royal Society for allowing me to reproduce their data as Figs. 1, 4, 5, 7, 8, 9, and 6, respectively, in this chapter. Special thanks to Professor Nori Satoh and Dr. Steven D. Aird, who checked my poor Japanese English carefully and gave me many useful comments and suggestions. Finally, I would like to acknowledge all members of my lab, past and present, who have always been supportive. I apologize that I could not fully quote sources due to limitations imposed upon the number of citations.


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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Marine Biological Laboratory, Graduate School of Integrated Science for LifeHiroshima UniversityOnomichiJapan

Section editors and affiliations

  • Ehab Abouheif
    • 1
  1. 1.Mc Gill UniversityMontrealCanada

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