What is the worlds smallest fish?

The Sinarapan?

Its the Goby which grows only as long as one centimeter less than half an inch. it swims in cool reefs in the western pacific.

Update -

Scientists have discovered a fish living in forest swamps on the Indonesian island of Sumatra that is only 7.9mm (0.311023622 inches) long.

The species of fish belongs to the carp family and is called Paedocypris progenetica . It is the world's smallest vertebrate or backboned animal.



Source: Natural History Museum, 25 Jan 2006

A small quibble with your post above, DG. In converting millimeters to inches you carry way too many decimal places. That last digit represents billionths of an inch, on the order of 10^-10.5 meters, making the expressed length accurate to about the nearest atom! (Check this.) "0.31 inches" will do.

That fish may be the smallest backboned species, but my brother-in-law has the world's smallest backbone.

Prof, I just used Google to get the figure and copied & pasted the answer. It's lazy, but quick. Until now, I assumed that it was accurate. But I do have a question about your link. Shouldn't

Earth = 12.76 x 10⁺⁶

be

Earth = 1.276 x 10⁺⁷...?



(Sorry about your brother-in-law.)

Yes, that's the convention with so-called scientific notation.

I think they expressed it the way they did to make it easy to speak of the earth's size in 'millions' of meters and plant cells in 'millionths' of meters.