>I have also found black-stained shells of various species that have
>been buried in anoxic sediment.  However, the Atlantic Jingle Shell,
>Anomia simplex, does occur in a black phase that is not the result
>of being buried, nor is it the result of algal growth. There are
>three distinct color forms of this species - yellow, orange, and
>black.  I have collected live specimens of all three. The black
>phase is the least common - well under 1% of specimens in any
>population I have observed.  Once I found all three color forms
>growing on one fist-size rock.  I have also found typical yellow
>forms with a definite greenish tinge that undoubtedly is due to
>algal growth.

Have you noted where the froms tend to live?

I have noted that wile Ischnochiton maorianus lives in anoxic mud on
the undersides of rocks, the shells are not blackened at all. I have
never seen living black anomiids, but then, most of the anomiids I
have seen in NZ have come up in deeper dredgings and tend to be
glassy colorless. Those I have seen intertidally or in shallow
dredgings have been greenish. The deep specimens are undescribed.
Heck, the intertidal ones may well be too... there certainly isn't
the "golden" form of northern-NZ A. trigonopsis here in the south.

When green algae live on shells it is usually obvious that there are
cells coating the shell. However in my P. macroschismus it looks as
though the green is due to shell-pigments; it is certainly not a
surface coating. Has anyone researched this?
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
Seashell, Macintosh, VW/Toyota van nut
‚ Opinions stated are mine, not of the University of Otago
"There is water at the bottom of the ocean"  - Talking Heads

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