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Title: Mechanics dictate where and how freshwater planarians fission

Abstract

Asexual freshwater planarians reproduce by tearing themselves into two pieces by a process called binary fission. The resulting head and tail pieces regenerate within about a week, forming two new worms. Understanding this process of ripping oneself into two parts poses a challenging biomechanical problem. Because planarians stop “doing it” at the slightest disturbance, this remained a centuries-old puzzle. In this paper, we focus on Dugesia japonica fission and show that it proceeds in three stages: a local constriction (“waist formation”), pulsation—which increases waist longitudinal stresses—and transverse rupture. We developed a linear mechanical model with a planarian represented by a thin shell. The model fully captures the pulsation dynamics leading to rupture and reproduces empirical time scales and stresses. It asserts that fission execution is a mechanical process. Moreover, we show that the location of waist formation, and thus fission, is determined by physical constraints. Together, our results demonstrate that where and how a planarian rips itself apart during asexual reproduction can be fully explained through biomechanics.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Univ. of California, San Diego, CA (United States)
Publication Date:
Research Org.:
Univ. of California, San Diego, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1529223
Grant/Contract Number:  
FG02-04ER54738
Resource Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 41; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; planarians; biomechanics; fission; rupture; traction forces

Citation Formats

Malinowski, Paul T., Cochet-Escartin, Olivier, Kaj, Kelson J., Ronan, Edward, Groisman, Alexander, Diamond, Patrick H., and Collins, Eva-Maria S. Mechanics dictate where and how freshwater planarians fission. United States: N. p., 2017. Web. doi:10.1073/pnas.1700762114.
Malinowski, Paul T., Cochet-Escartin, Olivier, Kaj, Kelson J., Ronan, Edward, Groisman, Alexander, Diamond, Patrick H., & Collins, Eva-Maria S. Mechanics dictate where and how freshwater planarians fission. United States. doi:10.1073/pnas.1700762114.
Malinowski, Paul T., Cochet-Escartin, Olivier, Kaj, Kelson J., Ronan, Edward, Groisman, Alexander, Diamond, Patrick H., and Collins, Eva-Maria S. Mon . "Mechanics dictate where and how freshwater planarians fission". United States. doi:10.1073/pnas.1700762114. https://www.osti.gov/servlets/purl/1529223.
@article{osti_1529223,
title = {Mechanics dictate where and how freshwater planarians fission},
author = {Malinowski, Paul T. and Cochet-Escartin, Olivier and Kaj, Kelson J. and Ronan, Edward and Groisman, Alexander and Diamond, Patrick H. and Collins, Eva-Maria S.},
abstractNote = {Asexual freshwater planarians reproduce by tearing themselves into two pieces by a process called binary fission. The resulting head and tail pieces regenerate within about a week, forming two new worms. Understanding this process of ripping oneself into two parts poses a challenging biomechanical problem. Because planarians stop “doing it” at the slightest disturbance, this remained a centuries-old puzzle. In this paper, we focus on Dugesia japonica fission and show that it proceeds in three stages: a local constriction (“waist formation”), pulsation—which increases waist longitudinal stresses—and transverse rupture. We developed a linear mechanical model with a planarian represented by a thin shell. The model fully captures the pulsation dynamics leading to rupture and reproduces empirical time scales and stresses. It asserts that fission execution is a mechanical process. Moreover, we show that the location of waist formation, and thus fission, is determined by physical constraints. Together, our results demonstrate that where and how a planarian rips itself apart during asexual reproduction can be fully explained through biomechanics.},
doi = {10.1073/pnas.1700762114},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 41,
volume = 114,
place = {United States},
year = {2017},
month = {9}
}

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Cited by: 8 works
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Figures / Tables:

Fig. 1 Fig. 1: Cartoon of D. japonica fission. (A) Unperturbed planarian before fission. The pharynx is marked by the blue arrowhead. To increase the fission rate (3), we amputate as indicated by the gray line. (B) Waist formation. Tissue movement causes local narrowing (orange arrowhead) and formation of wide contact regionsmore » at the head and tail (green arrowheads). The waist is not in contact with the surface. (C) The head lifts off the substrate during pulsation and then readheres and slides back against the surface. (D) Rupture.« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.