Sometime in October, Theresa Robot, an ultrasound technician at St. Francis Hospital in Evanston, will be back at the John G. Shedd Aquarium peering once again at the private parts of six Australian lungfish.
Earlier this summer Robot, who normally works with humans with high-risk pregnancies, helped solve an age-old-if faintly known-puzzle of science. In so doing, she set the stage for what could be an international coup for Shedd Aquarium:
She figured out how to tell the sex of a lungfish without cutting it open. That, in turn, might lead to the first successful breeding of the fish in an aquarium.
Among Robot’s subjects was “Grandpa,” or “Old Guy,” a 62-year-old lungfish that is not only the oldest animal in the Shedd but also the oldest known Australian lungfish in the world, captive or wild.
It’s a guy.
Already a profound oddity, the primitive lungfish, which first showed up before the dinosaurs and is equipped with a lung that allows it to breathe air like a land animal, exhibits no outward signs of sexual orientation.
That’s a deep problem for scientists who are scrambling to breed the endangered fish. There are only 19 of the big (2-foot, 20-pound) grey-green, eel-like fish in American aquariums.
With man-made pollutants and agriculture gradually destroying wild lungfish habitats in Australia, the government there releases very few to aquariums. The Australian lungfish is the most primitive of all forms, identical to 100-million-year-old skeletons of the fish.
If nobody succeeds in breeding them in captivity in this country, they will likely disappear completely from American aquariums as they die off and are not replaced.
The gender of most fish can be determined by coloration, fin shape or other external signs, but the lungfish keep their genders hidden internally. Using ultrasound imaging, Robot spotted the fish’s male and female sex organs.
Knowing the sex of each fish, however, isn’t enough to get them to reproduce. Among other things, aquarium workers will also have to know when the fish are feeling amorous, and they believe Robot will be able to help with that too.
Robot, working with Shedd Aquarium’s resident fish doctor, veterinarian Marty Greenwell, found that four of the Shedd’s fish are males and two are females.
In early 1994, the Australian government shipped five young adult lungfish to the Shedd in hopes that it will devise a successful captive breeding program.
For the last couple of years, Roger Klocek, the Shedd’s conservation curator, has been trying to figure out how to encourage the fish to get into the proper romantic mood.
The lungfish, contrary creatures, don’t make it easy. Breeding and sexual activity in almost all animals and plants is governed by what biologists call the “photo period,” the lengthening and shortening of daylight hours through seasonal changes.
For most animals, the gradually lengthening, warming days in springtime is what triggers their reproductive behavior.
For wild lungfish in Australia’s tropics, it is just the opposite. They get their reproductive motors started in the autumn, when days get shorter and the tropical rainy season cools their swimming holes, lowering the acidic content in their water.
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Though the lungfish at Shedd Aquarium live in artificial conditions, their days and nights are still governed by natural sunlight coming through the aquarium skylights. Now that autumn is approaching, Klocek has devised several other techniques to mimic the natural conditions.
For more than a year, all six lungfish have been living in a special habitat Klocek had built for them.
The habitat is a replica of 14 feet of an embankment where lungfish live in the Brisbane River in Australia.
The exhibit has real plants growing into the water, because in nature lungfish eggs attach themselves to the underwater leaves of such plants before hatching.
The exhibit’s 3,600-gallon tank also has its own, separate water system, so Klocek can manipulate water temperature and chemistry to simulate the Australian rainy season.
“About Sept. 15,” Klocek said, “we’ll start putting colder, softer water into the tank so that they’ll think it’s raining.
“We’ll let that continue for a couple of weeks, then we’ll ask Theresa Robot to come back early in October to do some ultrasounds to see if anything is happening.”
The fish will be captured individually in special traps, then tranferred to a pool of anesthetized water.
Once anesthetized, the fish will be removed from water and attached to a special machine devised at Shedd Aquarium that allows the fish to remain out of water but able to breathe through their gills. Then Robot will be able to pass an ultrasound “wand” over the fish, using sonar waves to make pictures of their internal sex organs.
“We’ll be looking for changes,” Greenwell said. “We’ll be looking to see if the males’ testes are becoming enlarged. We’ll especially be looking for ovary changes in the female, to see if there is ovarian follicle (egg) development.”
If the fish have reached that stage, Klocek said he would continue to manipulate the water to mimic autumn rains in Australia. If that is the proper “trigger,” he said, eventually the female will drop the eggs around the pool while writhing and dancing with the males, who are supposed to fertilize the eggs as they emerge.
Normally very slow-moving and phlegmatic, lungfish put on a formidably loud display of heavy breathing in the throes of passion.
Though they mostly breathe through their gills, when short of oxygen due to water conditions or exertion, they will also breathe through their lungs.
“I guess you could say that in the heat of passion, with all the activity, they’d need more oxygen and have to rise to the water surface a lot to get a deep sigh of breath,” Klocek said.
A year ago, Robot volunteered her expertise to Shedd Aquarium when it announced Tique, a Pacific white-sided dolphin in its collection, was pregnant.
Though that pregnancy was not successful, Greenwell was so impressed with Robot’s work, he asked her to ultrasound some African catfish that had been worrying him because of their bloated bellies. She did, showing that they were simply chubby from too much feeding, and he put them on a diet.
“What I really wanted to do,” said Greenwell, “is find a way to sex the lungfish. The only other way is to perform microsurgery on them, but I wanted a non-invasisve procedure, so I asked Theresa to try.”
Before doing the procedure, Robot had to study pickled lungfish specimens at the Field Museum of Natural History’s collection to find out what their sex organs looked like.
“I love animals,” Robot said, “so it’s been a spectacular experience for me. Working with the Shedd people was great. I couldn’t tell one fish from another, but they knew each one from their markings on their heads. Three Spot, Left Spot, Big Spot, Small Spot, No Spot and, of course, Grandpa.”
If any little ones eventually show up in the lungfish pool’s Spot family, Robot can probably add the title of “fish midwife” to her credentials.