Post by fabrizio on Jul 25, 2010 3:23:13 GMT
Sometimes, perhaps the same outcome could result either by genetic, or environmental/traumatic causes as well.
I heard even of a loosen columellar muscle, as a cause of "uncoiling"; yet I suspect this fact could be traumatic, of course, but even "inborn" and so perhaps hereditary... perhaps the same could be as to failed proper coiling of visceral mass, this could be a traumatic, as well as a "inborn defect"... And perhaps "switching on/off" of concerned genes, due to environmental stimula as Coyote suggests, could be still possible, I would suppose.
-We should carry out breeding experiments, if getting the chance to do, as repeated results could "prove" one hypothesis or the other, or both.
I read an old text, of a late '800 malacologist, whose "despiralized" Eobania passed apparently their trait to offspring.. although either images, and a "quantitative" description of the fact are both lacking in the said text (in italian).
Yet the fact that some species in remote environments, - Liobaicalia, some Caribbean Annularidae - have such "uncoiled" shells, would prove the possibility, for such trait, to become "fixedly acquired" and a peculiarity of the concerned species.
But in most of the ordinary environmental situations, such shape would be rather disadvantegeous, then "discarded" from Natural selection.
Something we could then obviate, in a captive and protected environment!
-As to the above fully shown Cepaea, its kind of despiralization is a "partial" one, as whorls are still adhering and coiling is still "compact".
This shape is quite common in other genera, proving it could be still a "physiological" fact, and would be interesting to adscertain if/at what degree it could be inherited.
It would be very interesting Robert, to know more about altitudinal linked differences in Arianta arbustorum shape!
It would be important, in the meanwhile, to know in which kind of habitat Crossless has found her Arianta arbustorum.
This shell is "middle-bulging" as I said, and by studying the heritability of such shape (perhaps even its enhancement), together with its being linked with this or that environment, could perhaps help to cast some light upon evolution of "pupoid/pupimorph" shapes, as the ones observed within Enidae, or Amphidromus.
-As Amphidromus and Enidae (or Vertiginidae, etc) belong to two quite distinct major lineages (namely, Sigmurethra the former and Orthurethra the latter two ), the trait "pupoid" of the shell could be regarded as having autonomously arisen at least twice, or even several times in different lineages.
-So, its appearence in still more lineage (Families, genera and species that usually don't exhibit it, as Arianta), could be quite possible.
-In this specific case, Amphidromus could perhaps represent better candidates for comparison, as 1) more (although loosely) related to Arianta (both families included in the same Super-family, Helicoidae ), and 2) having in common with Arianta a tree(shrub)-dwelling lifestyle.
Yet while Amphidromus sp. pl. are fully tree-dwelling, Arianta arbustorum can be found either in "tree" environment, or upon open land. ( www.weichtiere.at/english/gastropoda/terrestrial/helicidae.html )
So it would be remarkable to discover, for example, that "tree-dwelling" Arianta have such "middle bulging" shells (as the one of the tree-dwellers Amphidromus ), with greater frequence than "soil dwelling" Arianta.
..............
Each shell shape has surely its "history", resulting from a convergence of a basal genetic program at the very beginning, then casual mutations and finally adaptation due to habitat, sexual selection of lifestyles. It would be really exciting, trying to cast some more light upon the process, thorough observation carried upon the natural variability of "common", easy to get species!
-Robert, I find new to me, and very interesting indeed, your data about dextral shells reappearing from sinistral shelled snails mating!
It's a very complex matter indeed... as to the little I read about, the same sinistral coiling could be a "dominant" trait in some species, and a "recessive" one, in others...
-And I read that coiling is due to maternal inheritance, although I don't remember the details of explanations.
-So speciation that gave rise to sinistral Euhadra species could have been a still more long, tricky and haphazard process, than thought!
-It would be very interesting Robert to know more in details about sx/dx coiling inheritance, if you wish to explain that.
-Perhaps a dedicated topic would be better; and I hope even the above debated breeding project would be given each one a dedicated topic, to follow their developement and outcomes!
Kind Regards,
fabrizio
I heard even of a loosen columellar muscle, as a cause of "uncoiling"; yet I suspect this fact could be traumatic, of course, but even "inborn" and so perhaps hereditary... perhaps the same could be as to failed proper coiling of visceral mass, this could be a traumatic, as well as a "inborn defect"... And perhaps "switching on/off" of concerned genes, due to environmental stimula as Coyote suggests, could be still possible, I would suppose.
-We should carry out breeding experiments, if getting the chance to do, as repeated results could "prove" one hypothesis or the other, or both.
I read an old text, of a late '800 malacologist, whose "despiralized" Eobania passed apparently their trait to offspring.. although either images, and a "quantitative" description of the fact are both lacking in the said text (in italian).
Yet the fact that some species in remote environments, - Liobaicalia, some Caribbean Annularidae - have such "uncoiled" shells, would prove the possibility, for such trait, to become "fixedly acquired" and a peculiarity of the concerned species.
But in most of the ordinary environmental situations, such shape would be rather disadvantegeous, then "discarded" from Natural selection.
Something we could then obviate, in a captive and protected environment!
-As to the above fully shown Cepaea, its kind of despiralization is a "partial" one, as whorls are still adhering and coiling is still "compact".
This shape is quite common in other genera, proving it could be still a "physiological" fact, and would be interesting to adscertain if/at what degree it could be inherited.
It would be very interesting Robert, to know more about altitudinal linked differences in Arianta arbustorum shape!
It would be important, in the meanwhile, to know in which kind of habitat Crossless has found her Arianta arbustorum.
This shell is "middle-bulging" as I said, and by studying the heritability of such shape (perhaps even its enhancement), together with its being linked with this or that environment, could perhaps help to cast some light upon evolution of "pupoid/pupimorph" shapes, as the ones observed within Enidae, or Amphidromus.
-As Amphidromus and Enidae (or Vertiginidae, etc) belong to two quite distinct major lineages (namely, Sigmurethra the former and Orthurethra the latter two ), the trait "pupoid" of the shell could be regarded as having autonomously arisen at least twice, or even several times in different lineages.
-So, its appearence in still more lineage (Families, genera and species that usually don't exhibit it, as Arianta), could be quite possible.
-In this specific case, Amphidromus could perhaps represent better candidates for comparison, as 1) more (although loosely) related to Arianta (both families included in the same Super-family, Helicoidae ), and 2) having in common with Arianta a tree(shrub)-dwelling lifestyle.
Yet while Amphidromus sp. pl. are fully tree-dwelling, Arianta arbustorum can be found either in "tree" environment, or upon open land. ( www.weichtiere.at/english/gastropoda/terrestrial/helicidae.html )
So it would be remarkable to discover, for example, that "tree-dwelling" Arianta have such "middle bulging" shells (as the one of the tree-dwellers Amphidromus ), with greater frequence than "soil dwelling" Arianta.
..............
Each shell shape has surely its "history", resulting from a convergence of a basal genetic program at the very beginning, then casual mutations and finally adaptation due to habitat, sexual selection of lifestyles. It would be really exciting, trying to cast some more light upon the process, thorough observation carried upon the natural variability of "common", easy to get species!
-Robert, I find new to me, and very interesting indeed, your data about dextral shells reappearing from sinistral shelled snails mating!
It's a very complex matter indeed... as to the little I read about, the same sinistral coiling could be a "dominant" trait in some species, and a "recessive" one, in others...
-And I read that coiling is due to maternal inheritance, although I don't remember the details of explanations.
-So speciation that gave rise to sinistral Euhadra species could have been a still more long, tricky and haphazard process, than thought!
-It would be very interesting Robert to know more in details about sx/dx coiling inheritance, if you wish to explain that.
-Perhaps a dedicated topic would be better; and I hope even the above debated breeding project would be given each one a dedicated topic, to follow their developement and outcomes!
Kind Regards,
fabrizio