>
> This sounds like the "sinistral and dextral specimens must be
> different species>

Good argument, thought of that. However, sinistrality in normal dextral
species (and visa versa) of marine gastropods happens rarely, and more or
less at random. There are only very few cases in which sinistrality
succeeded in the development of a new species. Apparently, you need at least
TWO sinistral specimens of opposite sex (and lots of chance) to let it
happen. So one sinistral specimen means nothing, evolutionary speaking.
There could be an advantage in being sinistral sometimes (e.g. making a
predator unable to recognise you) but the geological record proves that
reversal of coiling is not a reliable driving force (and therefore not a
succesful trait) in gastropod evolution. Contrastingly, in isolated (island)
faunas there is a clear advantage in being a direct developer over being
planktotrophic. Whereas a species that as an adult lives in many yet usually
small and isolated habitats, has a clear advantage in reaching these
habitats by being planktotrophic as a veliger.

>"... or even subgenera... argument.

No, this is not a good rebuttal because it would imply that species sharing
the same type of protoconch are more related to eachother than those who
don't. Which is simply wrong (suppose that all non-planktotrophic triphorids
are more related to eachother than all planktotrophic species, then how come
that, say, Iniforis casta and I. turristhomae resemble eachother in a
combination of almost all their shell characters while there is a choice of
millions of such combinations?)


> If you take eggs from ONE capsule and hatch them under differing
> environmental conditions, and the larvae develop different types of
> protoconchs, what conclusion do you come to? That the single capsule
> contains eggs of more than one species?

Another good question. thought of that too: most if not all planktotrophic
species have the possibility to become non-planktotrophic, perhaps by
activating a suppressor gen, under the (yet unknown) right circumstances.
This is what happens in nature, this is of course what we should be able to
repeat in the lab. If you manage to convert the eggs of a specimen of a
planktotrophic species into non-planktotrophic larvae then by definition you
have indeed "created" a new species. And there is absolutely nothing wrong
with that.

Marien

> --
> Andrew Grebneff
> Dunedin, New Zealand
> 64 (3) 473-8863
> <[log in to unmask]>
> Fossil preparator
> Seashell, Macintosh & VW/Toyota van nut
> _________________________
> I want your sinistral gastropods!
> _________________________
> Q: Because it reverses the logical flow of conversation.
> A: Why is top posting frowned upon?
>