Friday Cephalopod: The good news about global warming

We’re making the planet a better place for cephalopods. It also helps that humans are busily destroying teleost populations.

David Wiltshire

P.S. There’s a video at the link titled “8 reasons octopuses rule the oceans”. Don’t bother with it. It is 8 incredibly idiotic reasons that have nothing to do with their success. I felt stupider after watching it.

Mystery structure explained!

That strange tissue I showed in a previous post is…the chorion of the embryonic zebrafish. It’s homologous to a structure called the zona pellucida in mammals, and it’s also made of the same stuff: a collection of highly conserved glycoproteins called ZP (for zona pellucida proteins) that form a tight extracellular matrix around the egg. There are four groups of related proteins creatively called ZPA, ZPB, ZPC, and ZPX, and most are found in fish, frogs, birds, reptiles, mammals — so they really are universal.

One distinction is that only mammalian ZPs/chorions have the property of sperm recognition — in other groups the chorion acts explicitly as a barrier to sperm entry. Fish have a tiny funnel-shaped hole in their chorions called the micropyle at the animal pole, which is just big enough to allow a single sperm to enter, reducing the likelihood of polyspermy.

What’s also cool about the chorion is that it inflates and self-assembles. It lifts off the surface of the egg at fertilization and expands, and further, enzymes are released from cortical granules in the egg to harden and toughen the coat. Basically when the egg is fertilized it quickly blows up a fluid-filled bubble around itself.

In zebrafish, the chorion is thin and transparent, and relatively easy to tear and remove. Other fish species may differ; the first time I tried removing the chorion from medaka, it was like trying to rip through tough leather after after being used to peeling away soft toilet paper. Chorions may also be decorated with threads or spiky processes, especially in demersal (sinking) eggs that need to stick to rocks or grasses at the bottom of a stream. Zebrafish are rather mundane and plain in comparison.

There are complicated things going on in the chorion: it’s a barrier and a filter. It blocks some toxic or teratogenic agents — there are some substances, like steroid-like plant alkaloids (cyclopamine, jervine) that are much more potent if you remove or even just tear a small hole in the chorion.

So about that photo: you are looking at a very thin sheet of a glycoprotein matrix that forms a kind of eggshell around the embryo. Most of the time I just rip it off and throw it away, but in this case I was scanning embryos and left it on, and as always, it struck me as lovely and intricately patterned.

Bonsignorio D., et al., 1996. Structure and macromolecular composition of the zebrafish egg chorion. Zygote, 4(02), pp.101-108.

Iwamatsu T et al. 1995. Changes in chorion proteins induced by the exudate released from the egg cortex at the time of fertilization in the teleost, Oryzias latipes. Development, Growth & Differentiation, 37: 747–759.

Murata K et al. 2014. Identification of the Origin and Localization of Chorion (Egg Envelope) Proteins in an Ancient Fish, the White Sturgeon, Acipenser transmontanus. Biol Reprod 90(6): 132.

Rizzo E et al. Oocyte surface in four teleost fish species postspawning and fertilization. 1998. Braz. arch. biol. technol., Curitiba , 41(1):37-48.

Zebrafish are so pretty

I was tinkering in the lab this morning, trying out a new gadget, collecting embryos, and cleaning and fine-tuning my microscope, when I saw this. Can you guess what I’m looking at?

Hints: shot at 40x, it’s not part of the embryo itself, and every zebrafish pro is thoroughly familiar with it.

There was a guess that it was yolk. No! I took a quick picture of the yolk sac in this same embryo, at the same magnification.

Those boulders at the top are cells, blastomeres. The bright band across the middle is the yolk syncytial layer, cells that bridge the gap between the cellular embryo and the yolk mass at the bottom. See? Nothing alike.

A few of you got it right, or came close: it’s the chorion.

More like “wary coexistence”

Annalee Newitz writes about the domestication history of house cats. They’re odd in that they haven’t been bred away from the standard wildcat, so the idea is that they’ve only recently been domesticated, and haven’t yet undergone extensive genetic selection. Interesting, but I must disagree with her closing statement.

Or maybe cats will continue to defy domestication. They could carve out a place as one of the only animals to befriend humans without ever falling completely under our control.

“Befriend”? She hasn’t met my cat.

The Face of Evil

Raychelle Burks explains how chemists would get rid of a body

I always thought the idea of getting rid of a body by dumping it in an acid bath was impractical and inefficient — it would take such a long time to break down, and would require so much in the way of chemicals. Raychelle Burks does the test, dropping chunks of pork in beakers of hydrochloric acid or sodium hydroxide, and my suspicions were confirmed. This is a bad way to do it. It’s also really gross.

You really need to get a biologist’s expertise for this job. My first thought was dermestid beetles — clean it down to bare bones, then mount the skeleton and store it in plain sight in the anatomy lab. You don’t have any beetles? There’s always Lord Dunsany’s solution.

But for simple practicality, just find a crematorium.

A new claim from the quack decapitator

Sergio Canavero is now claiming to have achieved successful repair/regeneration of severed spinal cords by something he pompously calls The Gemini Protocol. This is simply severing the cord with a sharp knife (good to know he’s not using a dull one) and immediately squirting the cut with polyethylene glycol (which we’ve known for decades will cause cells to fuse). He has photos of rats that he said managed to start walking again two weeks after slicing through their spinal cords.

This is pretty much guaranteed bullshit.

More qualified experts than I say the same thing.

Critics of the proposed human head transplant have been vocal since it was first announced. Commenting on it in 2015, Chad Gordon, professor neurological surgery at Johns Hopkins University, told BuzzFeed : “There’s no way he’s going to hook up somebody’s brain to someone’s spinal cord and have them be functional. On the conservative side, we’re about 100 years away from being able to figure this out. If he’s saying two, and he’s promising a living, breathing, talking, moving human being? He’s lying.”

Jerry Silver, Professor of Neurosciences at Case Western Reserve University, Ohio, works on repairing spinal cords after injury. Commenting on the latest study, he tells Newsweek it is unclear whether to team had truly severed the cord completely. “I notice that in the last paragraph they state ‘In conclusion, we have shown that the paralysis following full severance of the dorsal spinal cord can be reversed—to a significant extent—by immediate application of a fusogen.’ Did they sever only the ‘dorsal’ cord?” he says.

He said the team also claims the axons—which form part of the spinal cord—had regenerated, but “they show no evidence for regeneration.”

“There is no histology [the study of the microscopic structure of tissues] which is the only way to assess what is really going on here,” Silver said, adding the BBB scores—the scoring system used to assess motor function in rats—were unrealistic.

“Two treated animals supposedly recover locomotor skills that are nearly normal (BBB scores of 19 and 20 out of a possible 21 total) and as a group they average a score of 12 which means that they can on average take multiple weight bearing steps. [This is] unbelievable. Too good to be true in my opinion, which mandates that these results will have be independently verified and properly analyzed before this work can be accepted as scientifically valid.”

No histology. Partial cuts? Poor documentation of supposed recovery. This guy is a quack.

By the way, he’s also abruptly dropped plans to do the first human experiment on a man with a degenerative disease, Valery Spiridonov, and is instead planning to do it on an unnamed Chinese victim patient, just as he has announced Chinese government support.

Don’t take Canavero seriously, unless it’s to drag him off to the Hague for prosecution. His proposal is a glory-seeking sham.

The meeting circuit

Some people expressed surprise that I was at the Midwest Zebrafish meeting. They have meetings about zebrafish? How weird. Only not. What I find weird is that people are unaware of this mundane part of the science experience, so I thought I’d briefly explain it.

Every sub-sub-discipline does this. There are zebrafish meetings, fly meetings, worm meetings, mouse meetings, bat meetings. There are meetings dedicated to specific diseases. There are meetings for organs and tissues: brain meetings, kidney meetings, hair cell meetings, enteric nervous system meetings, ear meetings. There are meetings dedicated to the mechanisms of vomiting. There are meetings with 50 attendees, others with 30,000. They are going on in every city of the country all the time. We are right there under your nose.

Why do we hold these meetings?

  • Practice. It’s part of student training.

  • Networking. Bringing together people with similar interests is a great way to make connections.

  • Sharing new ideas. Sometimes an experiment might not be right for publication, so you get feedback on preliminary results.

  • Inspiration. We learn all kinds of cool stuff we can try in our labs.

  • Good times. You know how nice it is to hang out with weirdos with the same interests?

Who gets to go? Anyone. They’re open to anyone willing to pay for registration (which may be a few hundred dollars). You don’t want to go. It’s all very esoteric. This is where we let it all hang out: talks are wall-to-wall high-density jargon in which we assume everyone knows all the basics, or even the advanced stuff. It’s great, but lay people will be bored or lost. This stuff is often so rarefied and narrow that not even science journalists will be interested. It’s often condensed down to 12 minute talks — kind of like blipverts for the most technical stuff.

Sometimes people might wander by the hotel we’re having it in — it happened last night. The poster session for the meeting was held in the atrium, and we had a couple of people stop by and ask what it was all about. That’s great! We had a nice conversation and showed off some of our videos. Most scientists are happy to talk to anyone about the weird stuff we’re doing.

Now you know what it’s all about. Tomorrow I get to go home after an intense weekend…and I get to repeat it again in July.