Snails are underrepresented in your Reader’s wildlife photographs series. Meet three species here with a surprising characteristic. Did you know that some snails have hairy shells ? These hairs, which are mostly worn out in old individuals, possibly allow a better adherence on wet vegetal surfaces (reference below), but I’m skeptical and I would be glad if readers could suggest another adaptive explanation.
Reference: Pfenninger et al., 2005: Why do snails have hairs ? A bayesian inference of character evolution. BMC Evolutionary Biology 5, article number 59, Nov. 4, 2005
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And, from the back catalogue, great blue herons (Ardea herodias) from Stephen Barnard, including an optical illusion. Can you spot which photo has the illusion? (Answer at bottom). First, Stephen’s notes:
Sight fishing sequence in the creek behind my house. It caught a little fish but I missed the money shot. The photos were taken from indoors.
The illusion is in the first photo; Stephen explains:
When I shared this photo on some Facebook wildlife photography groups I was getting comments like “Great angle! How did you do it?” and I didn’t know what they were talking about. Then someone asked what was the thing in the sky sticking out of the clouds and I realized it was an illusion.
Snails? Must be a slow news day. :p
Stephen: Lucky you! What a spot you must have (we’ve seen the photos, so we know)!
I think the head of the heron in the last picture looks like a bunny head.
The snail hairs may indeed increase surface area and so add to their adhesion on wet leaves.
Another possibility is to somehow thwart arthropod predators, but the adhesion idea seems better to me somehow.
re: Why the Hairy Snail Shells?
I think Fashion is underrated in evolution. I don’t mean the obvious, ostentatious displays of things like peacocks and Donald Trump, but more as a personal statement.
So, my thesis is… rather than just being a “mating” thing, it’s more about being confident in oneself. They’re gastropods, after all. They could use a little boost, ya know?
The Pfenninger article cited in the post is here:
http://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-5-59
Clearly the snail hair is a form of sexual selection. Both male and female snails are irresistibly seduced by those sexy coifs.
Maybe they are young snails that want to look like a bad-ass mammal. They will grow out of it.
ha! most excellent.
The fact that these snails are hermaphrodites practizing simultaneous reciprocal fecondation doesn’t even weaken this interesting hypothesis…
Well, in the first place, you must not have seen the excellent Dreamworks documentary on snails, titled Turbo, which clearly documents their sexual dimorphism.
And in the second place, even hermaphrodites can be picky about their partners.
vive le pompadour!
The people who saw clouds in first picture must be from a warm climate. I had no trouble recognizing snow!
I saw clouds and interpreted it as an upward-angled shot (initially) and I am from a warm place. This matches your prediction, but in order to test the hypothesis we need more input from people who grew up with snow.
I saw snow right away. I’m in Ottawa.
I wondered how I missed seeing the sky people were talking about. I couldn’t turn that snow into sky.
But those are the cutest snails I have ever seen.
I agree, I could not see anything resembling clouds. Even when I go back to it I cannot make myself see anything other than snow…
I saw clouds, despite being currently in the midst of a snow squall near Toronto. Wishful thinking, perhaps? ( haven’t seen our local Harry da Heron this winter…)
I definitely saw clouds first, and we get plenty of snow here in Scotland (though not much this year so far). It was when trying to work out what the strange flying object poking through the clouds was, that it dawned on me.
Now I know, I can no longer see the illusion, no matter how hard I try.
The “hairs” are part of the periostracum, a thin layer of tissue that covers the shell. These are not part of the shell. A number of snail species have this characteristic.
Hmmm… the periostracum is usually considered as an intrinsic part of the shell, the first to be produced at the margin of the mantle of the growing snail. It is mostly proteinic, but is not alive, and very soon isolated from the living parts of the snail, therefore it cannot be considered as a tissue. The mineralised part of the shell is built between the mantle and the periostracum, which protect it from chemical (e.g. acidic) aggressions.
Gorgeous herons, Stephen!!
What did the snail say when it jumped on the tortoise’s back?
Wheeeeeeeeeeeeeeeeeeee!
Hairy snail shells?
l. Retain water droplets by capillary action thus slowing down drying and permitting more foraging time after wet spells? In dry habitats there would be little or no water and smooth snails would come out mainly on dewy nights.
2. Serve as physical deterrents to predators that swallow prey whole, such as salamanders, lizards and snakes? Salamanders are restricted to damp habitats, therefore the correlation with humidity. If in dry habitats snails are more nocturnal, they will be subject to reduced predation by lizards and birds and less prone to evolve (or retain) hirsute shells.
These and other adaptive hypothesis can be clarified through good natural history and tested with manipulative experiments, science’s gold-standard.
I think all the heron photos are optical illusions as I saw clouds at first in all three. My excuse: we haven’t had any snow here all winter.
I like to see those hairy S cars go!
Here in NZ we have many species of microsnails just a couple of mm in size. The best way to collect them is to chuck a handful of leaf litter in a bucket of water, and the empty dead shells float up to the top with the air inside.
Looking at the shells with a small lens you can see many of these tiny snails have highly ornamented shells, with whorls, short spines and all manner of other excrescences.
The reason for this ornamentation? No idea. You’d think it would actually be a disadvantage for such tiny beasts, adding to the friction as they creep through the leaf litter.
Re the heron photos Hang on isn’t the stuff in the back snow?? and judging from the shadows the last two shots are taken lower than where the grass sticks out from the snow and to the right of the stump plus the heron and background are larger – cutting out some features -plus I suspect a little to the left. i.e. could the first heron photo be zoomed taken very slightly to the left of the other two?
Love the pictures!
Where are these snails from?