The story behind Japanese Bitterling fish that determined pregnancy – Series 2 Episode 4


Welcome to another
Stories From The Stores We’re joined today by curator Sarah Bond and she’s told me that both these objects were used to detect pregnancy in the last hundred years. Sarah, how is this true? Both of them are used to detect a hormone in pregnant woman’s urine called HCG. Scientists first discovered this hormone in the 1920s. HCG is really important in preserving the pregnancy, in the very early stages before the placenta takes over and when you introduce most animals to this hormone they will ovulate. So the same scientists that discovered HCG found that if you injected it into immature female mice and rabbits they would start to ovulate and their sexual organs would mature, but the were expensive and they took quite a long time. Just one pregnancy test required five separate mice and all of them had to be dissected at the end of the process. So by the 1930s scientists were wondering could you use an animal that didn’t need to be dissected? These are a species of Japanese Bitterling, a tropical fish and as you can probably see they’ve got
quite translucent skins. The fish have an organ that they used to produce eggs
and that organ expands in the presence of HCG and so you can see how this works.
This first one here – its organ which is called an ovipositor – is quite a bit
longer than the second one which is a normal fish and the last one here is just been dissected to show that organ a little bit more clearly but essentially that organ would go all the way from about 2mm up to about 25mm. Was it super accurate? No not quite, unfortunately that was the
sticking point with this test. They weren’t very accurate and even men’s urine could often produce a positive result. So just a few years after the fish, a British zoologist working in South Africa found that if you injected a particular type of frog with pregnant women’s urine it would spontaneously lay eggs, what’s more it would do so within 12 hours. So if the animals are so good, why did it take so long to get to this? Well in fact the frog test, as it became known, was used up until the late 1960s and early 1970s and it absolutely was the standard pregnancy test all over the world. There was a lot of drive to develop a test that women could take in their own homes, just like this one which is an early home pregnancy test kit. They are still detecting exactly the same hormone it works from a different process, it’s a chemical
process so no animals are involved. So if the frogs took 12 hours, how long does this take? The very first chemical pregnancy
test took around 2 hours, which was still a vast improvement and now you can find
out the result in a matter of minutes. So if the animal test was so good would you still feel comfortable going back to the fish today? The fish not so much because
they were so unreliable, if the frog tests were still around and it was the
only option I had then sure, but at the end of the day it was so much easier
just to be able to walk into a chemist pick up a test like this, take it home and then I was the first person to find out I was pregnant.

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