-----Mensaje original-----
De: Cadee M.C. <[log in to unmask]>
Para: [log in to unmask] <[log in to unmask]>
Fecha: viernes 19 de febrero de 1999 11:16
Asunto: Re: Dark molluscs
 
 
>> ----------
>> From:         Antonio Jimenez[SMTP:[log in to unmask]]
>> Sent:         zaterdag 13 februari 1999 13:55
>> To:   [log in to unmask]
>> Subject:      Dark molluscs
>>
>> Hello, all:
>> a question: why most of the freshwater molluscs have dark shells or dark
>> bodies?
>> I am a recent member of the Conch-L and I am a novice and not specialized
>> collector.
>> Antonio Jimenez from Spain.
>>
>Dear Antonio, most freshwater mollusks are not dark, but if they are free
>from algae and other organisms, the shells of Limnaeidae and Planorbidae
are
>light yellow or white. With best regards, Martin Cadee, the Netherlands (a
>paradise for fresh water mollusks!)
> Dear Martin: I think what exists abundant examples of freshwater molluscs
what have dark shells ( in the families neritidae, thiaridae,
viviparidae,...) or dark bodies under translucent shells ( in physidae,
hydrobidae, planorbidae...). Marine and terrestrial molluscs have colours
not uniforms. I think what exists some characteristics specifics of the
freshwater environment what obligate this molluscs adopt this colour. A
general answer to this question I think  is difficult. May be due to
camouflage, but in many occasions I look dark molluscs over whitish rocks
 for example, Melanopsis praemorsa and Theodoxus fluviatilis over calcareous
rocks in my country, the South of Spain). Also may be due to protection in
cold climates (the dark colour absorb more energy of the sun rays), but also
exists dark freshwater molluscs in tropical region (Faunus ater and others
thyaridae). I suggest ( like a totally baseless hypothesis) a report with
our melanine (for protection of ultraviolet rays of sun). I don't know. Best
regards.
Antonio Jimenez.