Shufflebrain

As I was stacking the salamander dishes on the tray for transfer back into the main lab, I noticed that Buster had not taken his worm. This was impossible! My first thoughts were profanities against the bureaucrat who'd mashed the fire-alarm siren button. Maybe the noise had affected my animals! All the other animals had already devoured their worms. I checked the stock animals, and their appetites were fine, too. But Buster wasn't taking. Yet he was frisky enough and looked very healthy.

Now I had a suspicion. I ran into the main lab, filled two beakers with spring water from a carboy, and transferred six feisty-looking stock guppies into each beaker. One group I set beside the fish tank to fast overnight, at 20 degrees centigrade. The second group I chilled to 15 degrees centigrade by swirling the exterior of the beaker in cracked ice. When the thermometer hit the fifteen-degree mark, I transferred these guppies into the cool room and set them down next to Buster.

I allowed the guppies to acclimate for about an hour, using this time to check the feeding responses of the stock salamanders and the recipients of guppy hearts and then to wolf down my stale lunch. Finally it was time to check the chilled guppies.

I placed each guppy in a dish by itself. Then I dropped in a worm for each. The fish swam over at once (they're much quicker than salamanders) and inspected the worm. But, like Buster, the fish would not attack.

***

There was nothing unusual about a tropical fish refusing to eat live meat at cool temperatures. Their digestive enzymes become inefficient in the cold. Had my guppies' ancestors back in Trinidad ignored sudden drops in temperature and gone on eating worms they couldn't digest, the species would have vanished via natural selection, eons before my experiments with Buster's brains. The salamander, on the other hand, in a cool pond in early spring or late fall, can't afford to pass up a meal. General considerations notwithstanding, I held off on any conclusions, because I did not know the particulars--the details necessary to make this story ring crystal true. I decided to leave Buster and the guppies in the cool environment overnight. And I placed one fresh worm in each dish.

When I arrived the next morning, the first thing I did was check out the fasting guppies in the main lab. They went into a frenzy when I held worms above the beaker. When I released the squirming ball, it vanished almost as soon as it hit the surface of the water, as though attacked by a school of piranhas. The control fish kept at 20 degrees were hungry indeed, I noted.

Next, I went into the cool room to see what had happened there during the night. All the tubifexes in the dishes with Buster and the chilled guppies had survived. Everybody was still lively and healthy, by every criterion I could apply. But Buster and the guppies simply were not taking worms. Again, I checked feeding among the stock and the guppy-heart recipients. They attacked the worms immediately.

But wait! I wanted more data. Now came a critical test. For the next step was like back checking addition with subtraction. I transferred Buster and the guppies into the main lab, placed them in fresh water--20.4 degrees centigrade--from a carboy there, gave each a fresh worm, set the entire bunch on my desk, recorded the time in my notebook, and then sat down to watch.

Sixty-one minutes from the time I changed his water, Buster devoured his worm. It took 101 minutes for a guppy to make the first nibble; by 111 minutes, not a worm was left in any of the experimental bowls. Warming the water had revived their chilled appetites.

But like a crapshooter on a hot streak, I just couldn't stop. I added to the experiment some salamanders with guppy flank muscle transplanted to their abdominal cavities. I added some new guppies. And I transferred the group back to the cool room, where I fasted them for forty-eight hours before adding worms. When testing time came, all the control salamanders ate their worms. But Buster and the guppies did not. I decided to allow the trial to run an additional twenty-four hours, leaving Buster and the guppies each with a worm. Still they failed to take the prey. When I repeated the warming phase of the experiment, Buster went after his worm in 58 minutes and the guppies averaged an hour and a half.