le 24/10/04 0:07, J.F.A. à [log in to unmask] a écrit :

> Hello List:
>
>> Apart: why some volutes have that huge globous protoconchs (Livonia) while
> some others have a sharp apex(P. mirabilis)?
> Well, thanks in advance,
>
>
> Juan Francisco.
>
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 The spur-like apex of Provocator mirabilis is an enamel secretion made by
the posterior fold of the mantle. its true protoconch is hddin behind and is
normally rounded. The size of protoconch in Volutidae is due to two factors:
the one is indivdual and depends how many embryos are in the eggs capsule
the other is genetic, therefore generic. In most of the Volutidae species,
the direct development gives an evolutionary pressure to increase the size
of the protoconch, which probably makes a better protection for the babies!
--
 Patrice Bail
2 Square la Fontaine 75016 Paris
Tel:  +33 (1) 45253330
Fax: +33 (1) 40501390

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