Re: NANFA-- Rivulus reproduction

Bruce Stallsmith (
Thu, 30 Dec 1999 10:43:04 EST

The trick with marmoratus and other species is that while they can live in
fresh water without apparent stress, they may not be able to successfully
reproduce in fresh water. Living in the fresh water could interfere with
hormonal cues to ovulate, to actually produce the eggs, or the eggs may not
develop in fresh water. I kept marmoratus in fresh water last year, and they
didn't reproduce. If you check out Bruce Turner's marmoratus page he has
some excellent photos of marmoratus habitat. They live in a very specific
area, the interetidal zone of mangrove swamps or very similar mud flats,
where they mostly hide out in burrows and grab passing arthropods. (There's
nothing like a good tidal swamp!) But, who knows? They're still poorly

--Bruce Stallsmith
Huntsville, AL (way above tidal influence)

>I'm glad the subject of Rivulus marmoratus was brought up. I've been
>wondering about this fish for a while. The fact that they are the only
>Rivulus species found in the U.S. coupled with their unusual reproduction
>makes them unique indeed. Cool web page Bruce ; thanks for sharing! I'm
>wondering if these fish might be found to occur in freshwater using the
>techniques described in the web page. It states that they are "unknown in
>freshwater " , but I'm thinking that perhaps methods like seining which
>poor results with this species might have resulted in this conclusion, much
>like the perception of them being rare or of special concern. The fact that
>they can handle abrupt transitions from salt water to fresh in lab
>experiments and they are occasionally found in brackish water would seem to
>indicate that this is possible (could be an experiment for NANFA members in
>the vicinity of freshwater near the Florida coast).

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