Sunday 13 March 2011

Snail reproduction and mollusc birth control

One of my hobbies is snail-rearing. I started this when living in Dublin. In spring/summer 2007 it was so amazingly rainy (even for Irish people!) that thousands of snails could be seen in the gardens. It must have been really good news for birds.

I started to be interested in these animals, as I did not see many of them in dry, hot and full-of-concrete Madrid. When I left Ireland I brought three garden snails with me. And I continued my "collection" rearing snails from other countries such as Portugal, Andorra or Spain.

I saw them mating many times, but they appeared to be sterile, as they did not seem to be laying any eggs at all. Then I informed myself a bit, and I read that apparently this was because I was not putting any earth in the snail's box.

So I decided to make an experiment. There you go!

The idea: it is quite simple, the hypothesis to prove is

When earth is available, two snails will lay many fertile eggs after mating.

The material: a glass jar, two snails (apparently it does not matter the sex, as they are hermaphrodite) and some earth from the park down the street.

The method: The reason I used a jar was that in that moment I had seven snails in my snail box, and I did not want to have everyone's offspring, so I just chose two garden snails (one Irish and one Spanish, which happened to be called Yogurín and Tullido). The jar was small enough to keep them near to each other. To ensure ventilation I made small holes in the lid.

I left them in the "love jar" on 16th November 2009...

The measures: well, what can we mesure here? There are a few interesting things to measure, such as the amount of eggs, their viability and the time it took the little ones to hatch.

Happily, in less than 24 hours (!), on 17th November, at 1:20 AM, one of the lovers started laying eggs, here is the photo of that moment:

You can see about five eggs, and the head of the snail almost an inch into the earth. After some hours, the job was finished (next photo was taken at 9:55 PM). About sixty eggs buried and hidden from possible predators!

You can see them a bit better here:

Just in case you want to compare sizes, here they are next to a 50 euro cent coin:

As you can see, the egg cluster looks as big as the parent, it is incredible the fact that he/she was able to leave so many!

For logical reasons, I only kept four eggs. The other eggs were responsibly buried (and probably baby snails were born soon afterwards) in the very same spot where the Spanish parent was found, near the Alberche river, so no harm had been made to them, or to the environment (as there are already many similar snails mating and laying eggs over there anyway).

Here are the eggs I kept:

For some days I looked at the jar to see if the newborn snails were there. The eggs always looked exactly the same. Surprisingly, after eighteen days, on 5th December, they were there!

No shells appeared to be around (later I learned the first thing they eat is their own shell to get calcium). And the change was quite fast. A couple of days earlier they looked like white, small pellets, and then, suddenly... snails! Tiny, translucent but complete snails. For unknown reasons, only three out of four eggs were viable. The other one looked a bit elongated. But it is a good ratio anyway.

Just in case you are interested in sizes, here you have them on a one cent euro coin:

And here they are, in one of their first walks:

Conclusion: snail breeding is not that difficult! However, it seems I was a bit lucky as well. After this experience I tried to do the same with a couple of grove snails I brought from Portugal, and unhappily after many days they did not seem to give any results.

Just in case you wonder what happened to the snail family, the parents (after completing their normal life cycle) died at the age of three. One of the children disappeared (probably fled home, *sigh*). But the two remaining Irish-Spanish little ones grew into adulthood and have a happy snailly life at home. The photo below has been taken an hour ago.