Photoresponsivity and motility in the planarian
            <i>Schmidtea mediterranea</i>
            vary diurnally

Hinrichsen, Robert D.; Fabi, Jason L.; Craig, Suzanne; Rovins, Palmer S.; Cerwensky, Allison J.; Major, Robert J.; Ruby, Christina L.

doi:10.1080/07420528.2019.1683023

Cited by 5 publications

(4 citation statements)

References 8 publications

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“…(5) Molecular candidates for a time-keeper in flatworms could relate to expression of the gene Smed-Tim , a homolog of the mammalian Tim ( Tsoumtsa et al, 2017 ); genes that regulate circadian processes in other animals, including sponges, cnidarians, and fruit flies (e.g., Clock, per ) are absent in planarians ( Reitzel et al, 2010 ). Ultimately, an understanding of the exact machinery of the circadian clock in flatworms remains unknown ( Hinrichsen et al, 2019 ). Recording flatworms under constant dark conditions would provide insight into whether the bimodal pattern of night-time activity originates from clock regulation.…”

Section: Discussionmentioning

confidence: 99%

Persistence of Nocturnality in Decapitated and Bisected Flatworms

Omond

Lesku

2023

J Biol Rhythms

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The ability of flatworms to regenerate entire brain structures, and indeed much of their body from mere fragments of the whole animal, presents the unique opportunity to observe the development of day-night rhythms in adult animals. In many animals, young are arrhythmic, and their species-specific timing of activity develops as the animal matures. In this study, we created two flatworm cohorts, housed in isolation, that were regenerating either (1) the brain in a decapitated animal, or (2) major body structures in a bisected, tailless animal. In this way, we observed how bisection influenced the level of activity and diel rhythmicity, and how these developed as each flatworm regenerated. Here, we demonstrate that intact flatworms were predominantly active at night, with peaks in activity seen in the hours after lights-off and before lights-on. While decapitated and tailless flatworms could still move, both were less active than the original animal, and both segments retained a nocturnal lifestyle. Furthermore, decapitated flatworms, once regenerated, again showed a U-shaped pattern of nocturnal activity reminiscent of the two night-time peaks seen in the original animal. These results could be used to further investigate how regeneration may affect motor control and motor output, or to further investigate the presence of a clock in the flatworm brain.

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Section: Discussionmentioning

confidence: 99%

Persistence of Nocturnality in Decapitated and Bisected Flatworms

Omond

Lesku

2023

J Biol Rhythms

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“…Many phyla reproduce asexually, including annelids (Gibson and Harvey 2000 ; Kostyuchenko et al 2016 ), echinoderms (Jaeckle 1994 ; Rubilar et al 2005 ), cnidarians (Bell and Wolfe 1985 ; Lucas 2001 ), platyhelminthes (Saló 2006 ; Egger et al 2007 ) and arthropods (Banfield-Zanin and Leather 2015 ; Gutekunst et al 2018 ). Planarian asexual reproduction has been a well-documented phenomenon since the 1700s when well-known researchers such as Michael Faraday first recorded it (Hirshfeld 2006 ). Planarian asexual reproduction takes several forms including parthenogenesis and fission by fragmentation (Lentati 1970 ; Åkesson et al 2001 ; Egger et al 2007 ; Malinowski et al 2017 ).…”

Section: Introductionmentioning

confidence: 99%

The effect of stress on rates of asexual reproduction in an invasive planarian

Rock,

Oudendijk,

Kürten

et al. 2023

Ecotoxicology

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Animal reproduction under stressful conditions is often reduced, with current survival and future reproduction being generally traded off against current reproductive activity. This study examines the impacts of physical and chemical stressors on the rates of asexual reproduction of the invasive planarian Girardia tigrina. 320 wild-caught planaria (mixed size class) were kept individually in Petri dishes such that their individual rates of fission through fragmentation could be easily monitored. Four treatment groups were compared, one chemical (5 mg/L ammonia) and one physical (decapitation), in comparison to a negative control (animals were starved of food) and a positive control where the animals were given an abundance of food. The two treatment groups immediately began reproducing asexually and accumulated the highest number of fissions over the course of the 12-day investigation period, while the positive control only began to fission after 7 days. We propose that the reproductive response observed here is an adaptive one to stressful conditions, whereby the likelihood of survival through numerical abundance is enhanced, although the size and vulnerability of resulting fragments may impose a balancing cost. The response may play a role in the invasiveness of G. tigrina by making it able to colonize environments where adverse conditions prevail.

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“…A molecular time-keeper could come from the expression of the gene Smed-Tim in planarians, a homolog of the mammalian clock gene Tim (Tsoumtsa et al 2017 ). More conspicuously, flatworms are less active during the day—a diel rhythm that persists under constant dark conditions—and they appear to anticipate photoperiodic change (Omond et al 2017 ; Hinrichsen et al 2019 ). Furthermore, the production of melatonin, serotonin, and arylalkylamine N-acetyltransferase vary over a 24-h day under both 12:12 light:dark and constant dark regimes (Itoh et al 1999 ; Itoh and Igarashi 2000 ).…”

Section: Introductionmentioning

confidence: 99%

Why study sleep in flatworms?

Omond

Lesku

2023

J Comp Physiol B

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The behaviors that characterize sleep have been observed across a broad range of different species. While much attention has been placed on vertebrates (mostly mammals and birds), the grand diversity of invertebrates has gone largely unexplored. Here, we introduce the intrigue and special value in the study of sleeping platyhelminth flatworms. Flatworms are closely related to annelids and mollusks, and yet are comparatively simple. They lack a circulatory system, respiratory system, endocrine glands, a coelom, and an anus. They retain a central and peripheral nervous system, various sensory systems, and an ability to learn. Flatworms sleep, like other animals, a state which is regulated by prior sleep/wake history and by the neurotransmitter GABA. Furthermore, they possess a remarkable ability to regenerate from a mere fragment of the original animal. The regenerative capabilities of flatworms make them a unique bilaterally symmetric animal to study a link between sleep and neurodevelopment. Lastly, the recent applications of tools for probing the flatworm genome, metabolism, and brain activity make their entrance into the field of sleep research all the more timely.

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Photoresponsivity and motility in the planarian Schmidtea mediterranea vary diurnally

Cited by 5 publications

References 8 publications

Persistence of Nocturnality in Decapitated and Bisected Flatworms

Persistence of Nocturnality in Decapitated and Bisected Flatworms

The effect of stress on rates of asexual reproduction in an invasive planarian

Why study sleep in flatworms?

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