Dear Listers,
Some time ago we discussed the commensal biota on living coquina (Donax
spp.) clams. This site exemplifies this symbiosis:
<http://www.jaxshells.org/0726ur.htm>.
Harry
At Fri, 6 Feb 2004 19:20:50 I wrote:
Dear Andy and Kay,
I think you're both correct. Phyllis Johnson (1966) examined Donax gouldii
Dall, 1919 at La Jolla and Estero Beach (five miles north. She noted a
sparse growth of the colonial hydroid Clytia bakeri Torrey, 1904 in
October, 1964 and the following January, but by the following August (1965)
almost every living clam had a plume of Clytia, and the hydroid itself
supported an unidentified brown alga, which covered the entire plume.
In northeast Florida - actually at Crescent Beach, St. Johns Co. (!) - I
have found most of the specimens of D. variabilis have a commensal hydroid
on the posterior aspect of the shell (the short end; the upper end when
burrowing; the end with the siphons) when I collected in the summer months
(for broth on most occasions), and I don't recall seeing filamentous algae.
I think the hydroids are better able to gain a foothold on the shells (more
adhesive in the settling phase), and the algae probably need the hydroids
as a substrate for settling on the living coquinas. Perhaps later the alga
obscures the hydroid or even replaces it.
Andy, did you mean mobile, Mobile, or motile?
Harry
Johnson, P. T., 1966. On Donax and other sandy-beach inhabitants, The
Veliger 9(1): 29-30. July 1.
At 10:42 AM 2/6/2004, you wrote:
>Hi Kay,
>
> > When collecting Donax gouldii in Southern California as a child, I
> often found that the larger ones had tufts of algae on them. After
> reading your postings about the active little guys, I wonder how the
> seaweed had a chance to get a foothold (so to speak.)
>
>Could also be hydroids, which are a bit tougher than seaweeds. Remember,
>this is the part of the clam that sticks out into the water -- highly
>energetic, oxygenated, and nutritious water, plus currents generated by
>the Donax. Predators are nothing to worry about when you have a rapid
>burrower to carry you into the sediment and safety. A great place to live
>if you're a filter-feeder and like Donax exhaust.
>
>I think that this has been studied -- may have read about an analogous
>case in Fotheringay's 'Gulf of Mexico' book, which is probably in a box
>somewhere. Anyone have a copy of that to hand?
>
>In a similar case, I found the common Mulinia with balanid barnacles
>attached to the exposed end -- one barnacle on each valve, flattened where
>they abutted each other. But this was in the clay bottom of eastern
>Mississippi Sound, Alabama, a much quieter environment.
>
>Other examples of mobile bivalves that have other organisms living on them?
>
>Cheers,
>Andy
>Andrew K. Rindsberg
>Geological Survey of Alabama
Harry G. Lee
Suite 500
1801 Barrs St.
Jacksonville, FL 32204
USA
Voice: 904-384-6419
Fax: 904-388-6750
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Visit the Jacksonville Shell Club Home Page at:
www.jaxshells.org
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