# age: apropos of flatworm regeneration

<< Unlike most multicellular animals, planarian flatworms can regrow all their body parts after they are removed. This makes them a good model for studying the phenomenon of tissue regeneration. They are also useful for exploring fundamental questions in developmental biology about what underlies large-scale anatomical patterning. >>

Electrical signals kick off flatworm regeneration. Cell Press. Mar 5, 2019.

https://m.phys.org/news/2019-03-electrical-flatworm-regeneration.html 

AA << propose a simple model of molecular-genetic mechanisms to explain how physiological events taking place immediately after injury regulate the spatial distribution of downstream gene expression and anatomy of regenerating planaria. >>

Fallon Durant, Johanna Bischof, et al.
The Role of Early Bioelectric Signals in the Regeneration of Planarian Anterior/Posterior Polarity. Biophysical Journal. Vol 116, Issue 5, P948-961, Mar 5, 2019  doi: 10.1016/j.bpj.2019.01.029

https://www.cell.com/biophysj/fulltext/S0006-3495(19)30065-7  

# evol behav: apropos singular convergences, the case of the sea snail Elysia cholorotica; it's unique, controversial, elusive ...

<< Elysia cholorotica, a sea slug found off the U.S. East Coast, can steal photosynthetic plastids from algae and survive by basking in the sun. >>

<< It’s unique; it’s controversial; it’s elusive; it never eats, (..)  If you don’t know exactly where you’re looking and what you’re looking for, you won’t find it. >> Patrick Krug.

<< But these special slugs are becoming increasingly rare, and the small number of experts who studied them have mostly retired or have moved on to other areas. >>

Douglas Main. Solar-Powered Slugs Hide Wild Secrets-But They’re Vanishing. The photosynthetic sea slug, which lives off the U.S. East Coast, is becoming almost too rare to research. NatGeo. Jul 22, 2018.

https://relay.nationalgeographic.com/proxy/distribution/public/amp/animals/2018/07/solar-powered-photosynthetic-sea-slugs-in-decline-news

https://twitter.com/NatGeo/status/1112204138841034752

FonT

Elysia cholorotica, an example of a master in the game of life  ...

# evol: inside the "KT boundary", the day the dinosaurs died

<< When I saw that, I knew this wasn’t just any flood deposit, (..) We weren’t just near the KT boundary-this whole site is the KT boundary! (..) We have the whole KT event preserved in these sediments, (..) With this deposit, we can chart what happened the day the Cretaceous died. >> Robert DePalma.

<< No paleontological site remotely like it had ever been found, and, if DePalma’s hypothesis proves correct, the scientific value of the site will be immense. >>

Douglas Preston. The Day the Dinosaurs Died. A young paleontologist may have discovered a record of the most significant event in the history of life on Earth. The New Yorker. April 8, 2019 Issue.

https://www.newyorker.com/magazine/2019/04/08/the-day-the-dinosaurs-died    

<< When I first read it, I kept saying ‘wow, wow, wow,’ >> H. Jay Melosh.

Ryan F. Mandelbaum. Scientists Find Fossilized Fish That May Have Been Blasted by Debris From Asteroid That Ended the Dinosaur Age. Gizmodo.com Mar 29, 2019.

https://gizmodo.com/scientists-find-fossilized-fish-that-may-have-been-blas-1833671176  

William J. Broad,  Kenneth Chang. Fossil Site Reveals Day That Meteor Hit Earth and, Maybe, Wiped Out Dinosaurs. A jumble of entombed plants and creatures offers a vivid glimpse of the apocalypse that all but ended life 66 million years ago. NYT. Mar 29, 2019

https://www.nytimes.com/2019/03/29/science/dinosaurs-extinction-asteroid.html  

# gst: programmed cell death (apoptosis) also in algae

<< bacteria that live on single-cellular algae can cause programmed cell death. "It is the first documentation of true apoptosis via bacterial pathogens in microorganisms like algae," >>  Rebecca Case.

Study shows first evidence bacterial-induced apoptosis in algae. University of Alberta.  Mar 21, 2019.

https://m.phys.org/news/2019-03-evidence-bacterial-induced-apoptosis-algae.html    

Anna R. Bramucci, Rebecca J. Case.
Phaeobacter inhibens induces apoptosis-like programmed cell death in calcifying Emiliania huxleyi. Scientific Reports. Volume 9, Article number: 5215 (2019) March 21.

https://www.nature.com/articles/s41598-018-36847-6  

# gst geo: a model of a cascading, zig-zag fashion earthquake on weak crustal faults

<< The model confirmed that the Kaikoura earthquake involved a complex cascade of fault ruptures, which propagated in a zig-zag fashion. Propagation velocities along the individual fault systems were not unusually slow, but the complex geometry of the fault network and delays at the transitions between fault segments led to a tortuous rupture path.  >>

A surprising, cascading earthquake. Ludwig Maximilian University of Munich. Mar 20, 2019.

https://m.phys.org/news/2019-03-cascading-earthquake.html

<< the complex fault system operates at low apparent friction thanks to the combined effects of overpressurized fluids, low dynamic friction and stress concentrations induced by deep fault creep. >>

Thomas Ulrich, Alice-Agnes Gabriel, et al. Dynamic viability of the 2016 Mw 7.8 Kaikoura earthquake cascade on weak crustal faults. Nature Comm. volume 10, Article number: 1213 (2019) Mar 14

https://www.nature.com/articles/s41467-019-09125-w

# gst phyto: how cheaters are favored

<< Our data show that natural selection favors cheating rhizobia, and support predictions that rhizobia can often subvert plant defenses and evolve to exploit hosts, >> Joel Sachs.

<< The study (..) is the first to uncover cheater strains in natural populations and show how natural selection favors them. >>

Study finds natural selection favors cheaters. University of California - Riverside. Mar 19, 2019.

https://m.phys.org/news/2019-03-natural-favors-cheaters.html

<< Legumes have mechanisms to defend against rhizobia that fail to fix sufficient nitrogen, but these data support predictions that rhizobia can subvert plant defenses and evolve to exploit hosts. >>

Kelsey A. Gano‐Cohen, Camille E. Wendlandt, et al. Interspecific conflict and the evolution of ineffective rhizobia. Ecology Letters. Mar 18, 2019 doi: 10.1111/ele.13247

https://onlinelibrary.wiley.com/doi/full/10.1111/ele.13247

# gst: the auto assembly of a drop (from thermal capillary waves)

<< after single or multiple bridges form due to the presence of thermal capillary waves, the bridge growth commences in a thermal regime. Here, the bridges expand linearly in time much faster than the viscous-capillary speed due to collective molecular jumps near the bridge fronts. Transition to the classical hydrodynamic regime only occurs once the bridge radius exceeds a thermal length scale l_(T) ~ sqrt(Radius). >>

Sreehari Perumanath, Matthew K. Borg, et al. Droplet Coalescence is Initiated by Thermal Motion. Phys. Rev. Lett. 122, 104501 Mar 13, 2019.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.104501

Supercomputer sheds light on how droplets merge. University of Edinburgh. Mar 20, 2019.

https://m.phys.org/news/2019-03-supercomputer-droplets-merge.html