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Jon,

Here is an off-the-wall-hypothesis for you:  Several species with dorsal
filaments (tarpon, threadfin herring, threadfin shad) exhibit similar
"rolling" behaviors, in which the fish come to the surface and some of the
fish's dorsal surface is momentarily out of the water.  Could it be that
filaments on the dorsal fin provide some control during such "rolls" ?

Randy E. Edwards, Ph.D.
Research Fish Ecologist

USGS-BRD-FCSC
Center For Coastal & Regional Marine Studies
600 Fourth Street South
St. Petersburg, FL 33701-4846
Phone:  727/803-8747 (x3069)
FAX: 727/803-2031
[log in to unmask]

Do not tell fish stories where the people know you; but particularly, don't
tell them where they know the fish.  [Mark Twain]



                      Jon Shenker
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                      10/08/02 04:02
                      PM
                      Please respond
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An off-the-wall question:

Does anyone have any good hypotheses about the function of the elongated
dorsal filaments that are found in some fish species?

In the lower teleosts:
Tarpon have very long filaments, ladyfish don't.
Shafted bonefish (Albula nemoptera) has the dorsal filament, bonefish (A.
vulpes) don't.
Three or four North American clupeids have filaments, the rest don't.

In the elasmobranchs, many species have some sort of elongation of the
dorsal fin beyond the fin base, but the fin seems elongated into distinct
filaments in hammerhead, bonnetheads and others.

A hydrodynamic function?  Maybe in elasmos, who have larger, stiffer
filaments, but in the slender , flexible filaments of teleosts?
Why would some closely-related species have them, and others not?

Would removing a portion of the dorsal filament of a tarpon (for DNA
analysis) have an impact on the fish?

Any information or speculation would be welcome.

On another note:  My old copy of Reuben Lasker's (ed.) Marine Fish Larvae
has finally been shredded beyond repair before I found time to photocopy
it.
It's an oldie but a goodie for helping students get started in the larval
fish field.  I haven't had any luck finding a copy for sale in the used
book
web sites.  If anyone sees a copy for sale, please let me know.

Thanks.

Jon Shenker, Ph.D.
Associate Professor of Marine Biology and Aquaculture
Department of Biological Sciences
Florida Institute of Technology
150 West University Boulevard
Melbourne, FL 32901
321-674-8145
FAX 321-674-7238
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