Re: NANFA-- Great Lake Aquarium in Duluth Minnesota

Bruce Stallsmith (
Sun, 13 May 2001 14:39:15 -0400

Lake Victoria has a very different history than the "true" Rift Lakes such
as Malawi and Tanganyika. Victoria is very large (the size of Ireland) and
not very deep, it's essentially a huge swamp. The other Lakes are very deep
and have almost oceanic quality water; Tanganyika is probably about 12
million years old, the others somewhat younger. There is evidence that
Victoria comes and goes on a scale of about 10,000 years depending on shifts
in the climate. It apparently almost totally disappeared about 15,000 years
ago when world climate was cooler which affected monsoon patterns around the
Indian Ocean. As the climate warmed and the continental icesheets retreated,
rainfall increased and the lake once again spread. Interesting geophysical
history, to be sure, but even more interesting is genetic evidence that the
400 species of endemic haplochromine cichlids in the lake today are all
descended from one common ancestor at the time of the lake's rebirth. If you
analyze the DNA of existing fishes from the lake there's almost no
variablity even between species that appear and behave very differently. The
evolutionary history of such "species flocks" is one of the more interesting
studies in evolutionary biology today. (It probably has something to do with
regulatory functions in the DNA sequences, but that's another story.)

--Bruce Stallsmith
Huntsville, AL, US of A

>One exhibit claimed that Lake Victoria was only 12500 years old and had
>about 400 endemic fishes. Can anyone confirm this age for the lake for me?
>I thought the lake was a part of Africa's Rift Valley and would thus be
>old. I also thought it would take longer than 12500 years for species to
>evolve (even after taking into account year-around spawning).
>Mark Otnes
>Fargo ND

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