Animal without synapses feeds by external digestion using global, local cellular control

Animal without synapses feeds by external digestion using global, local cellular control
Trichoplax fed on microalgae (red specks). Credit: Carolyn Smith

A multicellular marine animal without organs, Trichoplax's feeding behavior may include cellular coordination, resulting in external food digestion, according to a study published September 2, 2015 in the open-access journal PLOS ONE by Carolyn Smith and colleagues from the National Institute of Health in Bethesda, MD.

Trichoplax is a small, disk-shaped marine metazoan animal without recognizable neurons and muscles that moves using hair-like cilia. Despite having only six cell types, whereas humans have about 200, and no nervous system, Trichoplax appears to coordinate a complex sequence of behaviors culminating in external digestion of . The authors of this study combined live cell imaging with electron microscopy to observe Trichoplax at scales ranging from the whole animal to subcellular.

They observed that when Trichoplax glides over a patch of algae, its cilia stop beating and it ceases moving, which indicates its ability to its the entire body. The authors then found that cells of a certain cell type, called lipophils, simultaneously secretes granules whose contents rapidly break down the algae. This secretion appears to be targeted, indicating that the organism has , as only lipophils near algae released the granules. Trichoplax also appeared to pause while the algal content was ingested, and then resumed gliding.

Global control of gliding seemed to be coordinated with precise local control of lipophil secretion, which the authors suggest indicates the presence of mechanisms for cellular communication and integration. The authors conclude that this level of mechanistic understanding of external digestion in a modern animal may provide a window to understanding the early evolution of digestion and the systems controlling it.


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More information: PLOS ONE, dx.plos.org/10.1371/journal.pone.0136098
Journal information: PLoS ONE

Citation: Animal without synapses feeds by external digestion using global, local cellular control (2015, September 2) retrieved 17 July 2019 from https://phys.org/news/2015-09-animal-synapses-external-digestion-global.html
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