Fish Study Shows Communication Differs by Gender
ROBERT SIEGEL, host:
So, you've probably been asking yourself how do male and female African electric fish communicate? Okay. You haven't been asking yourself that, but Professor Carl Hopkins of Cornell University has been. And he and his associates at Cornell have come up with some fascinating findings. The fish, it turns out, engage in a kind of electric courtship duet.
Professor Hopkins joins us from Ithaca, New York. He is a professor of neurobiology and behavior at Cornell. Welcome to the program.
Professor CARL HOPKINS (Neurobiology and Behavior, Cornell University): Thank you.
SIEGEL: And can you tell us first about the fish that you were studying and what kinds of fish these are?
Prof. HOPKINS: This fish that we work on are called Mormyrid fish. They generate weak electric signals using an organ, an electric organ located in the tail, which produces about a 10-volt discharge.
(Soundbite of electric current)
Prof. HOPKINS: And it's used for two things. First, navigation and it's also used for its communication.
SIEGEL: And what you have done here that's novel, as I understand, this is the degree to what you've been able to study that electric communication inside a tank at Cornell.
Prof. HOPKINS: That's right. We were successful in getting the fish to breed in the lab, which is really the gold standard for excellent laboratory conditions.
SIEGEL: I have read about how you and also your undergraduate student, who was working with you on this, Ryan Wong, in order to get the fish to breed, you had to replicate the rainy season from West Africa in the fish tank.
Prof. HOPKINS: That's correct. That was a wonderful discovery that's made by a German scientist by the name of Frank Kirschbaum. He discovered that if he lowered the water conductivity and sprayed water on the surface, that many of these electric fish would start to breed. And we replicated that recipe and it worked perfectly.
SIEGEL: You mean spraying the water on the surfaces, that's the rain. The fish would recognize that it's raining now.
Prof. HOPKINS: That's the rain. And we just got a sprinkler and sprayed water on the surface several hours per day.
SIEGEL: Which also means to these mormyrids, this fish, it's time to mate now.
Prof. HOPKINS: It's time to mate.
SIEGEL: If we were fish, we would think that was a great time at that point.
Prof. HOPKINS: That's a great time.
SIEGEL: Wonderful conditions. And that's when this electric communication takes on the courtship phase?
Prof. HOPKINS: That's correct. The males set up territories. Then they try to attract females and they mate with them. And it's quite elaborate and interesting.
SIEGEL: Now, you've been studying this fish for a while. Ultimately, is there something to be learned from the dueling electric duets of the mormyrids. Or we could call them elephantfish, yes? The same fish?
Prof. HOPKINS: Yes. Yes.
SIEGEL: Is there something to be learned that goes beyond mormyrids or elephantfish? Is there some larger truth about animal communication and courtship here?
Prof. HOPKINS: My former advisor when I was a student, Peter Marler, was fascinated by what he called design principles for the different modalities of communication. And he felt that there were features of sound, for example, that made it particularly good in one context or another. And we have tried to work on that principle with the electric modality also - one of the physical constraints on signals that might guide the evolution of certain kinds of patterns or displays.
SIEGEL: So what you have here is an example of a species that has somehow evolved into a method of communication, which permits courtship, which is remarkably well-adapted to these very peculiar habitats in which they live.
Prof. HOPKINS: I'm amazed that the patterns that we see in the courtship of this fish that Ryan Wong and I studied are very similar to a group of electric fish in South America called the gymnotiform fishes. During their courtship, they do very similar patterns. And we're not sure exactly why they have converged on these same kinds of signals, but there must be something there for future investigations to explain the convergence of the exact patterns of signals in these two independently evolved groups of fishes.
SIEGEL: Professor Hopkins, thank you very much for talking with us.
Prof. HOPKINS: Thank you.
SIEGEL: That's Carl Hopkins, professor of neurobiology and behavior at Cornell University in Ithaca, New York.
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