Some of our project students have been working on the feeding habits of garden snails Helix aspersa and one of our postgrads, Chantelle Kerr, drew my attention to the fact that some of their snails had been laying eggs in the tanks where we were keeping them. I was hoping to see some signs of the developing embryos when I took a look at these under the microscope, but the eggs were disappointingly cloudy. But then, on closer examination, the 'cloudiness' turned out to be something rather interesting. Take a look at the eggs on the microscope slide above and you can just about see clusters of white specks inside them (double click for a larger image), especially in the two at the back.
These turned out to be vast numbers of calcium carbonate crystals, embedded in the outer gelatinous egg capsule. The purple background colour is the result of using a colour filter to improve the contrast - not the real colour of the egg interior, which is colourless.
At higher magnification you can see that some crystals are simple cubes, while others are aggregated together. What are they for? Well, a quick search of the web reveals that the embryonic snails use this store of calcium to produce their first shell - the parent snail provides them with a supply of building materials for a shell when it lays the egg. You can read more about the chemistry of snail shells by visiting the excellent Snail's Tales blog.
Fascinating as always!ReplyDelete
Wow, what incredible photographs. We have raised snails, but I never thought to look at the eggs under a microscope.ReplyDelete
If the embryo is using those crystals to build its shell, then the number of crystals should decline as the embryo gets larger. I wonder if anyone has looked into that.ReplyDelete
A fascinating detail of everyday existence! It looks like someone sprinkled salt all over the shells in preparation for a nice snack. :) Perhaps the baby snail doesn't eat the shell until after it's hatched, rather than absorbing it gradually as it develops?ReplyDelete
Hi Alan, I had no idea that snail eggs could be so intersting!ReplyDelete
That was my reaction, eviltwit!ReplyDelete
Hi Roberta, me neither - up until the point that I looked at these I hadn't been feeling very benevolent towards the snails that eat my garden plants....ReplyDelete
Interesting thought Aydin - I wonder if they are used during development of eaten when the snail emerges from the egg? I wonder how the calcium is mobilised - change of pH? Acid secretion? I think theer were a few papers back in the 1980s - must have a look... best wishes, PhilReplyDelete
I think you might be right Jennifer - I have the eggs on my desk and am waiting for them to hatch....ReplyDelete
That is super-cool. I always thought snail eggs were nice to look at, but this takes them to a whole other level!ReplyDelete
Very interesting indeed! How large are the eggs to the naked eye. I think I may have seen some, but never thought them to be that of snails...! You may have the answer to our two year quandary!ReplyDelete
Hi falltoclimb, they always remind me of miniature pearls...ReplyDelete
Hi Petra, they are 2-3 mm. in diameter and usually laid in clusters of about 20, always in places where they'll remain moist until they hatch - under logs and stones and the like.......ReplyDelete