Absolutely agreed. My primary area of research was vascularisation, and I read a lot of zebrafish-based work and saw some awesome microscopy work at conferences. I would have loved to have worked with tools like this. It made my own efforts (3D collagen scaffolds with co-cultured HUVECS and smooth muscle) look utterly unrealistic and deeply flawed from the outset (which, in retrospect, they were).

> two copies of each chromosome, like humans, but unlike many other animals you might consider using

Could you elaborate on this a bit? I tried to look it up but only found that some insect males are haploid.

The thing i was thinking of is a rival frog, _Xenopus laevis_. That has been a classic model organism for research since the 1930s, and so ideally you would use that. But it's tetraploid - four copies of each chromosome. So are other related species of frog which are similarly useful. But not _X. tropicalis_ - that is basically "the Xenopus you can do genetics with!".

Zebrafish are diploid (i think), but their genome underwent a duplication during evolution, so they have two copies of each gene on each chromosome (more or less), which makes them hard to do genetics on in the same way as being tetraploid does.

uh? Zebrafish aren't transparent. They are white and stripped in metallic blue. Am I missing something here?

As the other comment mentions, the embryos are, but also, you can get amelanistic zebrafish.

This might be an interesting addition. You can't usually just buy zebrafish from Petco and use them for research. There are standards in animal facilities that determine whether your fish must be "specific pathogen free" or various other levels, and so you have to generally buy them from one of a few sources if you can't bum some from a beneficent lab. When we went to purchase embryos to set up a zebrafish colony (at something like $400 for 2 females and 1 male), the facility in Europe had suffered a fire that required them to stop production for 4-6 months.

As an aquarist I find this hilarious. For $399 you could hire an expert in fish pathology to check that the fishes are free from diseases and spend the other dollar into buying the real fishes, and put it in a quarantine tank then.

> the facility in Europe had suffered a fire that required them to stop production for 4-6 months.

This sounds very strange, unless you want to artificially create a scarcity in the supply of an animal that anybody can breed by thousands in their living room. You don't need almost any space to breed this fishes, and aquariums can be moved right?. 6 months seem too much.

I wonder why nobody has tried with another of the 100000 species of fish with transparent embryos and bypass this money-grabbing structure.

The issue is the genetic 'cleanliness' of the animals. Some zebrafish will only glow red when you feed them special stuff, some glow green, some only glow green in certain parts of their yolks/chorion. Sometimes this only happens with every other generation of females.

It's very complicated and quite 'messy' when it comes to the phylogeny/genetic trees. Most of the time, researchers only need those 20 fish or so once every few years, if that. Sometimes they need to interbreed these different fish to glow green and red. There are literally tens of thousands of types of fish that have to be kept. As an example: Jackson Labs has mice ready to order to the specific genotype that you want and it gets very specific [0]; zebrafish aren't quite at that level yet, but are getting there.

But the effort is worth it. Zebrafish are a great animal for studying neuro development and many other things. Many of the proposed treatments for ALS, Alzheimer's, Parkinson's, etc. got their start in zebrafish and in studying how those little vertebrates function. The effort will save countless human lives.

[0]https://www.jax.org/strain/008199

Sure, you can hire the fish pathology expert (or send samples out to a lab), but our facility requires us to have "clean" fish coming in, so we can't do the exercise of breeding, treating, and certifying fish in our own facility. The same is true of mice and rats. We have many pathologists on staff who could certify such a thing, but it would require setting up a "dirty" facility completely separate from the "clean" ones (complete with a separate animal care staff to change cages and such). Overall, the price is justifiable to avoid the trouble.

You wouldn't even need a different specie to bypass the money-grabbing, you only need a new facility, your own certified processes, and some clout in the industry (read citations). Hell, you could start with the fish from the expensive vendor and sell the offspring (I think, unless there's a licensing agreement involved).

Yes, sorry, the embryos are transparent - but so are the larvae, which is what i was thinking of:

https://www.youtube.com/watch?v=6v1Nfun5PqE

https://www.youtube.com/watch?v=0DB_Z0i5g_0

I don't know a lot about zebrafish (never did that postdoc), so i wasn't clear that larvae are a different stage to adults.

They are very easy. I had some long time ago and they even lay eggs and breed in my aquarium, but is not my favourite kind of fish for a community aquarium. Having evolved in clean and rapid rivers in India they are fast and nervous. Always darting and ready to engulf any food scrap. Can be a real source of stress for the other tank inhabitants and also for the owner (all you see most of the time is a blur when you try to observe your fishes).

I wonder how they can pick up a male and two females in a larvae pool. The sexual dimorfism on young zebrafishes is close to inexistent.

I had breeded fishes more transparent that those larvae, but must admit that the macrophage video is very cool.

the embryos are. so it's great for studying early development.