RE: NANFA-- Freshwater inverts

Hoover, Jan J WES (
Fri, 17 Dec 1999 13:08:12 -0600

>>>encrusting sheet type of freshwater sponge<<<

I've only seen small patches on submersed wood, but an invertebratologist
told me that sheets the "size of football fields" sometimes occurred in the
clear reservoirs of northeast Oklahoma. Growth forms of individual species
vary with local water conditions.

>>>I wonder if these sponges all need to be kept in a chilled tank. I'm also

thinking that perhaps the biologists needed to have more of a constant
of small organisms and have them in larger numbers and variety for the
sponges to filter feed<<<

You're probably right. Apparently cool water and constant infusions of food
(pond water, bacterial suspensions) were needed to keep them alive in
culture dishes. I'm guessing that Jorg's aquarium must have been generating
sufficient bacteria for them to feed. His observation about collecting too
late in the year also makes sense, although I'm surprised at gemmule-based
reproduction in aquaria. I was under the impression that gemmules required
some kind of stress cues prior to "hatching" like freezing or dessication.
I'd guess that in an aquarium reproduction might be sexual or via some other
asexual technique.

>>>I'm still wondering if any one can tell me whether freshwater feather
worms are North American and where they might be found at in this

yes - I looked it up because I was starting to wonder myself. There are
eight species (in three families) found in NA: four in California, 2 eastern
seaboard, 1 Great Lakes region, 1 cosmopolitan. I have a hunch that they're
more common than reports would indicate. Some oddball taxa of invertebrates
(e.g., hydroids, nemerteans) are encountered infrequently but are never
written up for the literature. As a result, their reported distributions are
spotty or fuzzy.

For info on freshwater feather dusters, see account in Pennak; also:

Foster, N. 1976. Freshwater polychaetes (Annelida) of North America.
Water Pollution Control Research Series, US Environmental Protection Agency,
Cincinnati, OH, 15 pp.

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