I think this is because snails only have one foot, so they can't walk like we do and they also can't jump or anything like that (imagine jumping snailies ). If you just had one foot and had to "walk" like that without jumping, you won't be very quick either . But I think there must be a more logical explanation
are you kidding me? next time you see your snail going up the side of its tank, just have a look at the muscle as it moves, snails are incredibly strong, they are quite easily capable of lifting there shells into awkward positions when aloft on the side of a tank, and when full grown, can also take passengers with them too on there shells. for the muscle factor snails have got it all, and as for the one foot... well there whole under body is just one big transportation muscle which i think deffintely compensates for the mono-foot dilema. saying that thou... snails have adapted that way through evolution, they ditched speed in favour of armoued protection (exo skeleton) though not 100% efficent (as is most noticable when looking at say.. a black throat monitors diet) its a good method of protection and one that has been used sinse life first exsited on earth. yet again that said, slugs are not the fastest of beasties either, and when i look at slugs it often makes me think that they are a dead end in the chain of molluscular evolution, simply because they have no form of protection. and do not compensate in any well known way for there lack of speed...
yes, slugs have a VERY sticky tough mucous, in 'Life in the undergrowth' ( a uk telovision program by Sir david Attenborough)a slug in the jungle was beigng attacked by some sort of cutter/warrior ants they broke their jaws on the think mucous, they got stuck in it, eventually they cut throught, but it took a while, and they had to get a whole legion of them to do so!
lool Snails are slow because they don´t need to be fast, their shell and their mucus are good protections. Their food is quite and doesn´t run off them ( well, I never saw a lettuce running) so they don´t need to spend energy capturing preys.With that they didn´t had any evolution pressure to be different, and so they are much alike their ancestors millions and millions years ago. In a micro-environment ( on the tree canopy)with few predators they didn´t evolved a shell at all, like in the humid tropical jungle of «El Yunque» in the island of Puerto Rico. Predators selective pressure plays an essential role on these matters.
Post by Robert Nordsieck on Aug 24, 2010 18:07:03 GMT
this may be an older posting, but I have some things to say anyway:
a) snail slime is hard to wash off, because it is hygroscopic: it contains mucopeptides that attract water, so the slime does not get dissolved in water.
b) snails are slow, because they have to overcome a very strong friction to the ground; there is a suction or underpressure, so the snail will not fall off. The slime lessens friction a bit, but, I assume, not so very much.
c) the snail shell is not an exoskeleton. A skeleton supports organs and the snail shell does not. The only muscle connected to a snail shell is the columella muscle or big retractor muscle that withdraws the snail into its shell. There is no motional musculature and the snail's body will maintain its form when the shell is removed, though the snail will die.
d) concerning heavy shells, even if they are very small, I think door snails are most spectacular in that regard - their shell is huge compared to their body. And still they can carry it and move not noticeably slower than other snails.
See this picture:
Common door snail (Alinda biplicata). Photo: Robert Nordsieck.
"These imperial snails will never get us" (Han Solo). "TaH pagh taHbe'!" (General Chang) "Once More Unto The Breach" (Henry V.)