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:

Malinowski, Paul T. ^[1]; Cochet-Escartin, Olivier ^[1]; Kaj, Kelson J. ^[1]; Ronan, Edward ^[1]; Groisman, Alexander ^[1]; Diamond, Patrick H. ^[1]; Collins, Eva-Maria S. ^[1]

---

+ Show Author Affiliations

1. Univ. of California, San Diego, CA (United States)

Publication Date:

Mon Sep 25 00:00:00 EDT 2017

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