Cephalic mechanism for social control of fissioning in planarians: III. Central nervous system centers of facilitation and inhibition.

Best, Jay Boyd; Abelein, Michal; Kreutzer, Erik W.; Pigon, A.

doi:10.1037/h0077164

Cited by 23 publications

(11 citation statements)

References 11 publications

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“…Specimens of clonal asexual Dugesia japonica were used for all fission experiments. Since planarians do not need a brain to fission, specimen were decapitated to increase the likelihood of fission in the presence of light (34). Details on planarian maintenance, fission experiments and analysis are provided in SI Materials and Methods.…”

Section: Methodsmentioning

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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Section: Methodsmentioning

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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“…Determining which of the physiological components of the fissioning system previously elucidated in the SCD Ss 1969, 1975Pigon et al, 1974 ;Morita & Best, 1984) have been altered in the BFH Ss will require further study .…”

Section: Resultsmentioning

confidence: 99%

“…Previously published studies on fissioning of asexual Dugesia dorotocephala revealed that : its incidence is suppressed in a graduated manner by cohorts ; it is more likely in longer than shorter specimens (Ss) ; it is modulated by photoperiod ; it occurs with a high incidence in decapitated Ss, irrespective of cohorts or photoperiod (Best et al, 1969(Best et al, , 1975Pigon et al ., 1974 ;Morita & Best, 1984) . All of these previous studies were done with laboratory cultures of Ss originally collected from a pond and stream fed from outflow from the Soldier Canyon Dam (SCD) approximately 6 miles northwest of Fort Collins, Colorado .…”

Section: Introductionmentioning

confidence: 99%

“…However, these exhibited marked differences in the more crowded conditions of laboratory culture : abnormally long, 30-50 mm specimens, seemingly unable to fission, developed . Since previous studies of asexual D. dorotocephala had revealed an inhibitory effect of cohorts on fissioning (Best et al, 1969(Best et al, , 1975Pigon et al, 1974), experiments were conducted with this new strain to ascertain the effect of population density (group size) on fissioning incidence . Results are described which show that this inhibitory effect of cohorts on fissioning is exaggerated in this new strain .…”

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confidence: 99%

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Abnormality in the fissioning control of a strain of asexual Dugesia dorotocephala found near Fort Collins, Colorado

Best

1995

Hydrobiologia

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Asexual Dugesia dorotocephala, collected from a new site several miles northwest of Fort Collins, Colorado, appeared similar, at the time of collection, to ones collected from other sites in the same general locale . However, these exhibited marked differences in the more crowded conditions of laboratory culture : abnormally long, 30-50 mm specimens, seemingly unable to fission, developed . Since previous studies of asexual D. dorotocephala had revealed an inhibitory effect of cohorts on fissioning (Best et al., 1969(Best et al., , 1975Pigon et al., 1974), experiments were conducted with this new strain to ascertain the effect of population density (group size) on fissioning incidence . Results are described which show that this inhibitory effect of cohorts on fissioning is exaggerated in this new strain .

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“…It has been reported that decapitated asexual worms show a higher rate of fission than intact worms, suggesting that the brain exerts an inhibiting control of fission (Kamatani, 1960;Best et al, 1969;Best et al, 1975;Morita, 1990). Indeed, the tail fragments from asexual worms underwent fission within a week of surgical ablation, whereas the head fragments started only began fission a month later.…”

Section: Critical Steps In Sexual Inductionmentioning

confidence: 94%