A few days ago Ron Bloomquist published at interesting photo of a ‘hiccuping’ intermittent snail trail on his Walking Fort Bragg blog, and was wondering how it might have come about (see http://walkingfortbragg.com/2009/07/so-how-foggy-was-it.html) .This snail wandered across my path today and this series of photos shows quite nicely how hit moves, with a head-to-tail wave of muscular contraction along its foot which is slightly arched – check out the way the gap under its foot moves backwards as the snail moves forwards in this top-to-bottom sequence (double-click the images for a larger, clearer view). It occurs to me that if the snail was crawling along a hot road surface and wanted to minimise the exposure of its foot to the heat it might well arch its foot even more, and might leave a trail like the one Ron saw...........just a thought.
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I believe you are on to something Mark. I have noticed the slime seems to come from the front of the snail and it slides the rest of it's "foot" across that initial slime spot. When the tail reaches the slime spot the front end is ready to lay down another spot. Maybe because of heat or maybe slime "rationing" when crossing long arid sections of concrete or dried ground. Or maybe snails always leave "spots" and I had never noticed before. I know slugs leave a continuous trail.
ReplyDeleteInteresting 'snails eye view' there Phil, in those shots.
ReplyDeleteAnd your 'thought' does make a lot of sense when you thin about.
Snail tracks on the cement of my porch and steps (not in the hot sun) are always like Ron's. I sort of presumed that it had something to do with the critters' locomotion.
ReplyDeletePleased you seem to have answered that Phil as I have been seeing the same sort of tracks on a tarmac path in the early mornings. Is it possible that slugs leave continuous trails and some snails leave intermitent ones - a difference in modes of locomotion?
ReplyDeleteLooks like you've cracked the problem, Ron. Slime rationing makes sense - it probably takes quite a lot of energy to produce..
ReplyDeleteHi Keith,sometimes snails get into my greenhouse and when they're crawling on the glass you can see the waves of muscular contraction travelling along their foot
ReplyDeleteHi John, now you come to mention it, it's certainly possible. Having a shell might have some influence on the way that the foot contracts. The interrupted slime trail might also be more evident in large snails than in smaller slugs
ReplyDeleteHi Granny J, there goes my 'tip-toeing across a hot path' theory. I think Ron has the definitive answer...........
ReplyDeleteGreat observation that, Phil. I've been ferreting about in books again and there is a muscle system that goes from the foot right up into the shell that might allow the snail to lift the central region, as in your photos, in a way that a shell-less slug might not be able to do. That would make it less important to lubricate the whole foot when moving so that an occasional dollop of mucous (which as Ron observed, is only formed in a gland just behind the snail's mouth) is enough rather than continuous production. Intriguing. If this is true then a comparably sized slug should make a continous trail. I'll take a closer look next time a Great Black Slug crosses my path....
ReplyDeleteAllan
Hi Nyctalus, I think that between you, me and the other commenters we may have pinned down the mystery of the interrupted slime trails.....such is the power of the web! My garden has more than it's fair share of black slugs, so I'll have a look too...
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