The news of a YouTube video of a live Punctum minutissimum, one of the smallest land snails in the world—but not the smallest—have been circulating lately in e-mails as well as various facebook and blog posts. Here is a shell of of Punctum minutissimum. This particular specimen was 1.3 mm in diameter.
I took this picture last November when I was visiting the Carnegie Museum of Natural History in Pittsburgh for the 3rd annual meeting of the Ohio (River) Valley Unified Malacologists. When I was getting ready to photograph this tiny shell I needed something to place it on. So I used this huge shell of the marine gastropod Cassis madagascariensis. Let my hand be the scale.
Yes, the Punctum shell was sitting at the apex of the Cassis shell.
The contrast between the sizes of these 2 distant relatives is striking, isn't it? Cassis started out from a protonch, an embryonic shell, that was perhaps only slightly larger than the adult Punctum, but grew to be about 200 times larger than the latter. There are snail species that are even larger than Cassis madagascariensis and others that are even slightly smaller than Punctum minutissimum.
Are equally drastic size differences observed between the largest and smallest members of other animal groups? I will write about that in another post.
Here is a post comparing Punctum minutissimum to Neohelix albolabris, the largest native land snail in eastern North America.