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What is a segment?

Roberta L Hannibal, Nipam H Patel1

  • 1Departments of Molecular and Cell Biology and Integrative Biology, University of California, 519A LSA #3200, Berkeley, CA 94720-3200, USA. nipam@uclink.berkeley.edu.

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|December 19, 2013
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Summary
This summary is machine-generated.

Defining animal segmentation remains challenging. This study reviews historical definitions and current debates, proposing a broader definition to unify diverse biological research on segmented structures.

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Area of Science:

  • Developmental Biology
  • Evolutionary Biology
  • Comparative Anatomy

Background:

  • Animal segmentation, the repetition of body units along the anterior-posterior axis, has been recognized for over two millennia.
  • Despite its long history, a universally accepted precise definition of segmentation is still lacking.
  • Ongoing scientific discourse highlights controversies regarding the composition and extent of segments across different animal groups.

Purpose of the Study:

  • To provide a historical overview of the definition of animal segmentation.
  • To discuss current controversies and debates in defining what constitutes a segment.
  • To propose a refined, more inclusive definition of segmentation to facilitate interdisciplinary research.

Main Methods:

  • Historical literature review on the concept of segmentation.
  • Analysis of current scientific debates on segmentation criteria.
  • Synthesis of diverse examples of segmented structures in animals.

Main Results:

  • A historical review reveals the evolution of segmentation definitions.
  • Key controversies include segment composition (tissue layers, single cells), and the segmentation of the vertebrate and arthropod heads.
  • A general definition of segmentation as the repetition of anterior-posterior polarized units is proposed.

Conclusions:

  • The lack of a precise definition hinders comparative studies of segmentation.
  • A broader definition of segmentation, emphasizing anterior-posterior polarity and unit repetition, is recommended.
  • Combining this general definition with specific descriptions and hypotheses will enhance scientific communication on segmental structures.