The More the Merrier?

Quinodoz, Sofia A.; Thomas, Michael A.; Dunkel, Jörn; Schötz, Eva-Maria

doi:10.1007/s10955-011-0157-3

Cited by 7 publications

(25 citation statements)

References 27 publications

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“…Statistical analysis of the reproductive behavior of individual worms in isolation revealed that S-planarians exhibit a randomized reproductive strategy with respect to the number of offspring produced per reproductive event. The distribution of offspring was well described by a maximum relative entropy principle for certain types of worms within the population [25]. Furthermore, we showed that S-planarians appear to regulate their reproductive cycles partially through their size at birth and partially through a stochastic term whose nature remains unknown [12,37].…”

Section: Introductionmentioning

confidence: 72%

“…Worm reproductive waiting times (RWTs) and the type of reproductive event (fission vs. fragmentation) were recorded as previously described in Ref. [25]. Death rates were calculated by dividing the number of worms which died before undergoing Teilung by the total number of worms that have reproduced.…”

Section: Isolated Worm Experimentsmentioning

confidence: 99%

“…Using such a large-scale, long-term experiment [36] tracking thousands of reproductive events, we have previously studied, both experimentally and theoretically, the life history strategy of S-planarians in great detail [12,25,37]. Statistical analysis of the reproductive behavior of individual worms in isolation revealed that S-planarians exhibit a randomized reproductive strategy with respect to the number of offspring produced per reproductive event.…”

Section: Introductionmentioning

confidence: 99%

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To Each His Own

et al. 2015

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Planarians are among the most complex animals with the ability to regenerate complete organisms from small tissue pieces. This ability allows them to reproduce by splitting themselves into a head and a tail piece, making them a rare example of asexual reproduction via transverse fission in multi-cellular organisms. Due to the stochastic nature of long reproductive cycles, which range from days to months, few and primarily qualitative studies have been conducted to understand the reproductive behaviors of asexual planarians. We have executed the largest long-term study on planarian asexual reproduction to date, tracking more than 23,000 reproductive events of three common planarian species found in Europe, North America, and Asia, respectively: Schmidtea mediterranea, Dugesia tigrina, and Dugesia japonica. This unique data collection allowed us to perform a detailed statistical analysis of their reproductive strategies. Since the three species share a similar anatomy and mode of reproduction by transverse division, we were surprised to find that each species had acquired its own distinct strategy for optimizing its reproductive success. We statistically examined each strategy, associated trade-offs, and the potential regulatory mechanisms on the population level. Interestingly, models for cell cycle length regulation in unicellular organisms could be directly applied to describe reproductive cycle lengths of planarians, despite the difference in underlying biological mechanisms. Finally, we exam-Electronic supplementary material The online version of this article (ined the ecological implications of each strategy through intra-and inter-species competition experiments and found that D. japonica outcompeted the other two species due to its relatively equal distribution of resources on head and tail pieces, its cannibalistic behaviors and ability to thrive in crowded environments. These results show that this species would pose a serious threat to endogenous planarian populations if accidentally introduced in their habitats.

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Section: Introductionmentioning

confidence: 72%

Section: Isolated Worm Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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To Each His Own

et al. 2015

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“…Fission is the sole mode of reproduction of the asexual planarians studied here, which poses the question of how this species creates population diversity. Where a planarian divides affects the fitness and reproductive behaviors of its offspring (7,(11)(12)(13). Therefore, understanding how fission location is regulated is an important evolutionary question to be answered.…”

Section: Discussionmentioning

confidence: 99%

“…One must limit oneself to giving the general trends and looks of this phenomenon without trying to explain all the observed exceptions" [author translation] (10). Because where along the body axis a planarian divides affects the fitness and reproductive behaviors of its offspring (7,(11)(12)(13), understanding how fission location is regulated is an important question to be answered. Regarding the division process, Vandel described fission as a mechanical process, whereby the anterior and posterior parts act independently, with the anterior part rhythmically pulsing and the posterior part largely adhering to the substrate.…”

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confidence: 99%

Mechanics dictate where and how freshwater planarians fission

Malinowski

Cochet‐Escartin

Kaj

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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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. Since planarians stop "doing it" at the slightest disturbance, this remained a centuries-old puzzle. We focus on Dugesia japonica fission and show that it proceeds in three stages: a local constriction ("waist formation"), pulsationwhich 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. Furthermore, 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.Keywords: planarians, biomechanics, fission, rupture, traction forces Significance Statement: How planarians reproduce by ripping themselves into a head and a tail piece, which subsequently regenerate into two new worms, is a centuries-old biomechanics problem. Michael Faraday contemplated how this feat can be achieved in the 1800s, but it remained unanswered because it is experimentally difficult to observe planarians "doing it". We recorded Dugesia japonica planarians in the act and developed a physical model which captures pivotal steps of their reproduction dynamics. The model reproduces experimental time scales and rupture stresses without fit parameters. The key to rupture is a local reduction of the animal's cross-sectional area, which greatly amplifies the stresses exerted by the planarian's musculature and enables rupture at substrate stresses in the Pa range. \body Already Michael Faraday and his contemporaries were intrigued by the observation that asexual freshwater planarians, squishy worms a few mm in length, reproduced by tearing themselves into a head and tail offspring, in a process called binary fission (1). How was it possible for these animals to generate the forces necessary to rip themselves using only their

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