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Post by brunni on May 28, 2011 13:26:30 GMT
Earlier this month, Robert Nordsieck provided us with a number of excellent links concerning the way snail shells are coiled. He mentioned : -.......... phenomenon among the Roman snail (Helix pomatia). Among thousands of specifically dextral shells there may be one or the other rare sinistral specimen. Those then are colloquially referred to as snail kings. - ..........Looking at the frequency of right and left handed shells in Roman snails, numbers alone (there may only be one snail king among some ten thousand Roman snails. Like Roman snails, tiger snails are normally dextrally coiled. Having been able to examine many thousands of tiger snail shells, I also found a couple with reverse coiling. Attached is an image of one found in the Ivory Coast. The first image has a mobile fone in the background, the second one I put my watch in the aperture ( its easy to mirror a photo image ! ). Attachments:
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coyote
Archachatina papyracea
Cochleas ego amo
Posts: 2,955
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Post by coyote on May 29, 2011 4:40:09 GMT
You are correct, it is a little too easy to mirror a photo image! I have seen pics of snail kings without any such context to set aside any doubt that the image was true. Using the cell phone and watch to provide a context is clever.  |
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Post by Robert Nordsieck on Jun 2, 2011 21:19:17 GMT
There is a page by the Jacksonville Shell Club (as in Jacksonville, Florida) showing pictures of different sinistral snail shells, terrestrial and marine, as I recall: www.jaxshells.org/reverse.htmKind regards Robert |
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Post by brunni on Jun 3, 2011 16:32:35 GMT
Thanks Robert for this link. I also noticed that some of these land snails (e.g. the colorful Amphridomus) have some species where left and right hand coiling occurs on a even scale. But in the Achatinidae sinistral shells are very rare. The only exception being the three known species of Columna and Archachatina bicarinata which are always sinistral. Interestingly, all these species are endemic to the islands of Sao Tome and Principe in the Gulf of Guinea. |
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Post by Robert Nordsieck on Jun 4, 2011 22:15:28 GMT
Is that inside the same species (sinistral and dextral)? I always thought the species was more or less specific in the coiling direction. I must admit though that my knowledge of so-called exotic snails is severely limited. By the way, the link to the posting referred to was: petsnails.proboards.com/index.cgi?board=general&action=display&thread=10387. I also read an article that in Japan is snail species has been found with a rather unusual rate of sinistral specimens in some areas. This is because of predation by snail-eating snakes (which I particularly dislike, first they eat snails, second they are snakes). Anyway, those snails have more teeth on one side (because the snails are asymmetric) and so the sinistral one have an advantage over the dextral ones. It has been said that sinistral snails appear so rarely in nature because they have difficulties in mating (all on the wrong side). I cannot confirm that. On one hand, snails, at least Roman snails, have always difficulties in copulating (many tries, few hits, much time, which basically is a good thing), on the other there is the picture by Peter Leonhardt showing a dextral and a sinistral snail mating and everything appears normal... Regards Robert |
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Post by brunni on Jun 5, 2011 17:22:22 GMT
Well Robert there are a number of Amphridromus species around the island of Java which seem to coil both ways. They are rather colorful and magnificent shells. Here is an example in the illustration : Amphidromus butoti , Laidlaw & Solem, 1961Amphridromus species (for example) in the Philippines tend to all coil one way, or the other. They are also beautiful shells....but a little different. It seems some INSULAR populations do not conform to the norm (an insular population is a population stuck on an island with nowhere else to go) ! Back to my comment about the Achitinidae of west Africa : the odd man/men out ( in coiling direction ) was/were the insular populations of Sao Tome/Principe. Is there an explanation for this ? The island of Hawaii is another point in mind................New Zealand............. Attachments:
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Post by Robert Nordsieck on Jun 6, 2011 21:52:35 GMT
Thank you very much for this information ;D
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Post by brunni on Jun 9, 2011 15:46:10 GMT
The tiger king found a friend............. Attachments:
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