09 July 2004

Eyeshine in an electric fish

Forrest,

I am most interested in the fish Apteronous albifrons. In the U.S. it is called the Black Ghost knife and is locally (Argentina) called the
Ituy. They are in the class of fish which are called "electric fish." That is they operate as a dipole antennae from head to near the tail. The most notorious is the so called electric eel that uses its cells to stun prey and for protection. The Ituy uses "the antennae" for location and food procurement.

Most aquarists believe that the Ituy is nearly blind and relies upon
it's electrical senses to navigate and forage. I would like to dispel
that concept using your recent article [Forrest M. Mims III, "Eyeshine and red eye," The Citizen Scientist, 2 July 2004, www.sas.org/tcs/weeklyIssues/2004-07-02/mimsci/index.html].

Of the numerous fish that I keep, the Ituy has the most reflective red eyes that I have seen, with the exception of the crayfish.

Regards,

Doug Graham

Please send us a report of any findings you make on the ability of the Ituy to see. Editor.

John Dooley on weather and the Moon

Editor,

Regarding Kevin Kilty's interesting article on weather and the moon, the wavelet spectrum indicates that the pressure amplitude peaks occur no more than once per year and last no more than 2 months. The simplest model that I can imagine has the moon effect adding with one or more other effects with different (but similar) period(s). Sometimes they happen to add constructively and produce a noticeable signal in the pressure amplitude.

If the extra signal were simply from the sun, I'd expect the peaks to appear more regularly. It looks as though there is an interesting third perturbation to the pressure. I wonder if there is a correlation between the peaks and lunar eclipses.

John Dooley

Professor John Dooley is a regular contributor to The Citizen Scientist. He has written many articles on experimental studies of sound waves. Editor.