Support the International Humanists and Ethical Union

The IHEU is launching a fundraising campaign to help humanists at risk around the world.

Over the last 5 years, the IHEU has led the way in providing advocacy and support for humanists at risk around the world.

The IHEU is at the forefront of identifying and raising awareness of a disturbing new trend:

— growing violence and discrimination targeted at non-religious individuals and groups around the world.

We want to continue highlighting and campaigning on this topic and defending individual humanists at risk. And we need your help.

They’ve been working to end blasphemy laws, which are used to selectively oppress humanists, and they’ve been assisting threatened individuals in relocating. This is a very good group, and they deserve all of your support.

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.

Republicans win another one

So Ossoff was defeated by Handel in Georgia’s 6th congressional district. Are you getting tired of this? I’m getting tired of this.

Karen Handel is simply a terrible human being, and she wasn’t shy about broadcasting it. She’s a smug conservative Christian who hates gay and trans people, demonstrating once again that the Republicans have a solid base among the bigots. Not only does it not damage her electability among Republicans, but expect the media to tut-tut afterwards about calling the terrible human beings who voted for a terrible human being terrible human beings. And hey, it seems appealing to bigotry is a great way to get out the vote.

The Democrats, as usual, followed their standard strategy: find an upper middle class centrist, typically a white man in a nice suit, and give them lots of money and demand that they follow a cautious, inoffensive, and ultimately uninspiring path. Triangulate tactically to put up the Least Worst Candidate. That simply doesn’t work when you’re dealing with the Bold Candidate from Hell. Shouldn’t we have learned our lesson from Trump?

How about if instead we drew on our base? More black grandmothers who are fed up at seeing their sons shot or thrown into prison. More middle class labor workers who are smart enough to see through the lies of management. Remember the Carrier air conditioning deal? Trump knew that whatever happened would be to the advantage of the people who owned the company, not the workers, and he just lied. If you’re going to promote a white man in a suit, at least make sure it’s one who is willing to align himself with the interests of the working class and the poor, and is willing to say things that antagonize rich donors but might get people to actually turn out and vote.

Oh, well. The bright side of the story is that once again the Republicans have confirmed their solid commitment to evil, with yet another Republican representative who ought to make any decent, humane person sick.

I guess that’s the bright side.

It’s not very reassuring.


Jesus fucking christ. Police dashcam video of the Philando Castile murder has been released, and I made the mistake of watching it. The car is pulled over, the cop explains that he was pulled over for a broken break light, he asks for license and registration, the driver calmly tells him that he carries a gun, and then the cop freaks out and starts yelling and unloads his handgun into the car. Seven shots! It’s horrific.

Later, the murderer is telling his fellow gunmen that Castile had been acting “hinky” and was looking directly into his eyes (truly a criminal act). The only one “hinky” here is the cop, who panics at a traffic stop and slaughters a citizen.

Jeronimo Yanez was acquitted, unbelievably. I hope he’s not working in any position that requires that he be armed anymore — he is a coward unsuited to any stressful situation — and I look forward to the civil suit that should strip him of everything he owns.

Read the statement given by the murder-cop after he killed that man. Would you believe that he was afraid for the little girl in the car, and that he had reason to think Castile might be a stone-cold killer because he was exposing that poor girl to second-hand smoke?

He got off because of that callous kind of lie.

Conversation with an ex-creationist

I’ve never been a believer, so who am I to say how to convince others to leave their faith? Tonight at 7pm Central, I’ll have a conversation with Glenn D., a former true believer who even donated money to Answers in Genesis, but has now seen the Light. Let’s find out what it took.

If you have questions you’d like me to ask, feel free to leave them here; he’s also commented here before so maybe he’ll answer you directly.

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