| Photo by Jane Scherr |
Roy Caldwell Interview: Conversations with History; Institute of International Studies, UC Berkeley
| Photo by Jane Scherr |
Page 3 of 8
Once you got into zoology and biology, did you expect to wind up with a focus on invertebrate marine biology or did that surprise you?
That surprised me a lot. When I started out, my Ph.D. dissertation was looking at insect migration. It was looking at milkweed bugs in Iowa and how they found their way around. And then I had a chance to spend a couple of summers in Bermuda looking at stomatopod, mantis shrimp, and then I went back to doing insect migration, and looking at the hormonal control of it for a post-doc in England. And then, as luck would have it, Berkeley was looking for a marine invertebrate behaviorist. I had all of two months experience, applied for the job -- I don't think they were very impressed with my marine invertebrate behavior, but I did know a lot about population ecology and physiology and genetics -- and I got the job. I figured I'd better become what they wanted, so I've been doing marine invertebrate behavior ever since.
I read a piece in which you wrote of "the growing satisfaction and occasional excitement of unraveling the biology of this creature." Tell us a little about this creature that you've focused so much on, the stomatopod.
Stomatopods are marine crustaceans. The all live in the sea.
They are a very old group; they evolved probably about 400 million years ago. They are characterized by what we call a raptorial appendage. It's a pair of arms that are folded up underneath the head, and they strike out and catch their prey with them. They are analogous to the arms of a praying mantis, so that give stomatopods their common name of mantis shrimp. The difference is that the praying mantis strikes at a fly from overhead, whereas as a stomatopod strikes underhanded. Also, the strike of a praying mantis is about 100 milliseconds, about the amount of time that it takes you to blink your eye. The strike of a mantis shrimp can be two milliseconds, about fifty times faster. It's one of the fastest known animal movements. With the evolution of that appendage came a weapon system, a feeding system, and just about every aspect of the biology of this beast is wrapped up with that weapon system. That's really what got me interested in them. Here's an animal which literally can kill his opponent with a single blow. I first started working on communication and aggression; now we're doing more work on reproduction and sensory systems. It's all coupled with how you deal with this armament and a very nasty and lethal weapon system.
There's a distinction that you make in your writing between "spearers" and "smashers." Help us understand that.
It's a functional distinction. The first stomatopods probably made their living sifting through the mud, scrabbling, looking for things to eat -- small animals. And probably what happened is that occasionally little creatures would be scared up and would be flushed and the animals evolved a pair of elongated arms which could reach out and grab these fleeing prey. The first stomatopods had a barbed appendage which they used to reach out and spear or impale the prey. They'd pull it back in, subdue it and eat it. Several times in the evolution of this group, that appendage then changed into what I call a smashing appendage or a hammer.
Here's the way it works. Let's say my hand is a series of spines. If I want to stab something soft, like a shrimp, I can just stab it and pull it in. But let's say I've got something like a clam and I want to open it up. There's a lot of meat in there. But hooking at it with barbs doesn't do any good. So one of the things the animals do is they fold this piece of the appendage back and they hit with the elbow. And that will break the clam shell. But if that becomes more enlarged and stronger, they can break stronger and stronger prey: crabs, snails, big clams. And that gives them this really impressive weapon system, which is also really useful against other stomatopods. So, the spearers are living on fish and shrimp and soft-bodied prey and they are relying on speed to impale them and pull them in and eat them. The smashers go out, find something heavy, hard, break it up.
You mention you began focusing on both the aggression and the communication system that went with that aggression. What in your background led you to that particular interest or focus?
An interest in weapons, for one thing. I was an archer and a fencer.
The story of how I got into it goes back to a blizzard in Iowa. I was working with my major professor, Hugh Dingle, and we were reading some papers about communication. There was a new technique called information theory analysis which had just come out, to look at how much the behavior of one animal influences another.
It takes lots and lots of data for that to work. Hugh had been in Bermuda as a graduate student and had seen these little animals that fought like crazy and he said, "You know, these animals would be great for working on that."
Well, as luck would have it, we were working on a cricket that day, and we came out of the lab about 3:00 in the morning, looked out the window, and there was a foot of snow and fifty mile-per-hour winds, and we couldn't go anywhere. We started talking more and more about this communication. And also, how do you get out of Iowa in the middle of winter? He said, "Bermuda's great, and these animals live there." So we ended up writing a grant, and that's how I first started working on it. It was to look at how information was exchanged between these animals. And I've basically been doing it ever since.
You said in one of your writings that "studying the morphology, the behavior, and ecology of stomatopods helped me understand the interdependence of each in the evolution of the whole." I want to take that as a platform, because here you have a very aggressive creature, and you became interested in that function and what it required, in a way, to actually deploy the weapon. Is that fair?
Yes. Usually in the evolution of a system you can't change one component without it affecting all of the others. And this is one of the prime examples of that. You add in a major weapon system, and now there is a need for information, good communication, good assessment capabilities. This weapon will dictate where the animals live, what kind of resources it uses, what it eats -- every aspect of its biology. So by looking at them, I never know whether I'm going to be working the next year on how they see, how they smell or how they catch prey or what have you. But it always comes back to this weapon, how it has evolved and what they do with it.
In our earlier conversation about studying this animal and other creatures, you said that you can almost talk about arms races. What did you mean by that?
As a weapon increases in power, animals have to deploy some sort of defenses against it, particularly if they're competing with others of their species. Think of it this way. Let's say the animal evolves, becomes bigger and bigger. As it becomes bigger, the power of the strike will increase exponentially -- actually increases with the cross-sectional area of the muscle which powers the thing. Now, the major defense against that strike is the thickness of the body armor, [but] the thickness of the armor only increases two dimensionally. It can get thicker, but if you have an animal and it grows larger and larger, the power of the strike will increase faster than the strength of the armor. At some point you have an animal that probably has a weapon which is capable of breaking down any armor that can be laid down, and that has happened several times in the evolution of this group. One of the neat things about it is that in one of the groups of species where this has occurred, they have become very colorful, they use a lot of displays, and they rarely fight. They usually stand back at a distance and wave at each other, and basically say "I'm bigger than you are, and please go away."
We're talking about the stomatopods here.
We're talking about stomatopods. Now another, actually fairly closely related group has also gotten large but it doesn't have bright colors, and it doesn't have a lot of displays. When two of them meet, they attack, and they go for a kill. So the question is, why? Why does one of them go in for all this displaying and bluffing and communication and the other one just go in and attacks? It has to do with what they're fighting over. The one that displays digs burrows. Burrows are pretty cheap. It takes a few hours to dig one. So it's probably not worth risking your life for a home. The other one, which is the hawk, which goes for the kill, lives in pre-existing rock cavities, which are very scarce. They have to fight for them. So it's the value of the resource base in which they are competing which dictates how they settle their differences.
So the focus on this one creature leads you, as you concentrate on it, from its morphology to its ecology.
Its behavior, yes.
Do all biologists get focused on one particular animal or are there variations? Do some come into biology and say, "Oh I'm really interested in aggression"?
Of those people who study animals, I always think that there are types. There is the one that's interested in a particular function or a process. So they're interested in flight or aggression or game theory or something of that nature. And they try to pick animal models which will help them address those general problems. The other kind of biologist, which is my kind of biologist, is the one who works on one group of animals, gets to know that group very, very well, and then sort of allows the animal to pose questions. Very often we don't know all the latest technology or have all the specific knowledge of the problems, so then we collaborate with colleagues and the two of us work together and try to address these issues. I can't say that one is right over the other. If you work on systems and go pick an animal, you have to spend a lot of time learning how to take care of that animal, catch it, maintain it, do what you need to with it. On the other hand, if you work on an animal you've got to figure out the problems. Very often both types of biologists get together, as I do with several of my colleagues, and it's a very synergistic relationship. It works quite well.
Next page: Doing Underwater Research
© Copyright 2001, Regents of the University of California