Cell and Tissue Research

, Volume 377, Issue 3, pp 309–320 | Cite as

Molecular and evolutionary aspects of the protochordate digestive system

  • Satoshi Nakayama
  • Toshio Sekiguchi
  • Michio OgasawaraEmail author


The digestive system is a functional unit consisting of an endodermal tubular structure (alimentary canal) and accessory organs that function in nutrition processing in most triploblastic animals. Various morphologies and apparatuses are formed depending on the phylogenetical relationship and food habits of the specific species. Nutrition processing and morphogenesis of the alimentary canal and accessory organs have both been investigated in vertebrates, mainly humans and mammals. When attempting to understand the evolutionary processes that led to the vertebrate digestive system, however, it is useful to examine other chordates, specifically protochordates, which share fundamental functional and morphogenetic molecules with vertebrates, which also possess non-duplicated genomes. In protochordates, basic anatomical and physiological studies have mainly described the characteristic traits of suspension feeders. Recent progress in genome sequencing has allowed researchers to comprehensively detail protochordate genes and has compared the genetic backgrounds among chordate nutrition processing and alimentary canal/accessory organ systems based on genomic information. Gene expression analyses have revealed spatiotemporal gene expression profiles in protochordate alimentary canals. Additionally, to investigate the basis of morphological diversity in the chordate alimentary canal and accessory organs, evolutionary developmental research has examined developmental transcription factors related to morphogenesis and anterior-posterior pattering of the alimentary canal and accessory organs. In this review, we summarize the current knowledge of molecules involved in nutrition processing and the development of the alimentary canal and accessory organs with innate immune and endocrine roles in protochordates and we explore the molecular basis for understanding the evolution of the chordate digestive system.


Digestive system Lancelets Tunicates Gene expression Evolution 



We would like to thank Editage ( for English language editing.

Funding information

This work is supported by JSPS KAKENHI Grant Number JP17J06306 and the cooperative research program of the Institute of Nature and Environmental Technology, Kanazawa University Accept No. 18040.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This article does not contain any studies with human participants performed by any of the authors.


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© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.The Graduate School of ScienceChiba UniversityChibaJapan
  2. 2.The Noto Marine Laboratory, Division of Marine Environmental Studies, Institute of Nature and Environmental TechnologyKanazawa UniversityHosu-gunJapan

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