Hi Milan

>Anyone knows WHY certain molluscan familes prevail in chemosynthetic
>environments (hydrothermal vents, cold hydrocarbon seeps, whalefalls...) ?

Why do some families give rise to more sinistral species and/or
abnormalities? Must be something in the genes which predisposes them,
or at least allows them to take advantage.

>The majority(?) of gastropods is represented by Clypeosectidae, Cyathermiidae,
>Lepetodrillidae, Neomphalidae, Peltospiridae, Pyropeltidae, Scissurelidae ,
>all related to limpets.

Clypeosectidae is in Fissurelloidea, unrelated to limpets;
Scissurellidae is distantly related to these (and far more distantly
to Pleurotomariidae!); Lepetodrilidae appears to be related to these
families as well, rather than to the limpets (Daniel Geiger and Jim
McLean have been doing a lot of work on some of these most
interesting families).

>OK, there are also Buccinidae, Trochidae and Turridae, but primitive limpet-
>related snails prevail.
>Among bivalves mytilidae & vesicomyidae seem to outnumber other families.
>
>In case that hydrothermal vents are cradle of life it is reasonable to expect
>that primitive limpet-related gastropods will prevail, but as far as I know
>most taxa "returned" to vents from normal environments. Only Neomphalidae show
>long term in situ evolution. So, what enables certain groups of molluscs to
>invade chemosynthetic environment?

Environments similar to these vents may originally been the
startingpoint for life, but molluscs weren't around then, and i very
much doubt that they originated there. So the presence of "primitive"
molluscs on the smokers is purely coincidental.

Work needs to be done, probably, on the metabolisms of all of the
vent fauna... I don't doubt that some of the species there are not
chemosynthetic, but merely feed on available foodsources there
because just because they are available. The toxicity of the
environment and the chemosynthetic organisms, as well as of those
organisms feeding on the chemosynthetic bacteria etc, is one possible
reason for the apparent paucity of predatory gastropods around the
vents.
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
<[log in to unmask]>
Seashell, Macintosh, VW/Toyota van nut

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