When someone tries to work out how something works there's a lot of tinkering plus trial and error that goes on. My project is aiming to understand how the blood and circulatory system forms in the embryos of vertebrates, so in some way I need to poke around with the inner workings of this complex mechanism, to see how everything fits together.
Fish are a fantastic choice for this type of research as they offer a balance between ease and relevance/morals. For instance if you're going to investigate how a Ferrari engine works, the most relevant model to work with is a Ferrari, however there aren't that many of them, they're super expensive and some would argue that taking a Ferrari engine to pieces is morally wrong. At the other end of the scale we have the wind-up toy car- this costs practically nothing, they are easily available and no one is going to be upset when they get taken to pieces. However a toy car really is nothing like a Ferrari, yes it has wheels, axles and cogs like the Ferrari but how these are arranged are completely different.
In this analogy the Ferrari is like a human, if we want to understand our own biological processes and try out disease treatments the most accurate test subject is a human. However some people frown on cutting up babies for research... Ptsh!! The toy car on the other hand is like a very simple organism such as yeast- these are single celled fungi so more complex than bacteria but still a huge way off humans. We can learn some basic principles from studying them but these may not be conserved (i.e. the same) in more complex organisms such as mammals.
So back to the fish. Fish are like mopeds (small petrol driven bikes). They look completely different to a Ferrari but actually share a huge number of features such as pistons, brake systems and a petrol driven motor. What we discover in zebrafish is likely to be strongly related to the same process in humans, especially the key components which are crucial for the function of the motor/ survival of the animal.
A pair of zebrafish can lay hundreds of embryos every week and these reach maturity (i.e. can lay embryos themselves) at roughly three months of age. Another great feature of fish is how the zygote (fertilised egg) is formed: zebrafish are "scatter spawners" so embryos are formed outside the body of the adult and can easily be collected for study without any harm to the adult. In mammals however the embryo grows within the mother so to study these really crucial and early stages the embryos have to be removed from the mother- often harming all those involved. The embryos also develop on a very pleasant time frame- by 24 hours one cell has divided and differentiated (developed into a variety of tissue types) sufficiently for a functioning heart to start circulating blood, eye and ear have formed and the tiny fish can start to beat its tiny tail (ahh cute!). A major bonus of fish research is it's much cheaper and easier to maintain 100,000 zebrafish than 100,000 mice, thus research funding can go much further. Finally zebrafish embryos are see-through so we can see all the internal organs developing, blood circulating and the heart contracting without any need to dissect or treat the embryo. Only at 3-4 days post fertilisation so they start to loose their translucent nature.
All round zebrafish are pretty damn awesome.
Basically that's why today I am happy that my fish, who have been living out in L.A. for five months, have finally started laying fertile embryos of their own. This means tomorrow I will be able to look at them under the microscope and hopefully get some pictures for you guys.
'Till then be most excellent to each other,
L
ps: in no way do I condone testing on human children, even if they are screaming and disgusting germ-ridden little brats. Their parents are probably more suitable anyway...
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