If all goes well, within a year or so keepers at the Shedd Aquarium hope to hear some heavy breathing coming from its newest exhibit in its tropical freshwater fish gallery.
On Thursday the keepers placed the oldest living Australian lungfish, which came to the Shedd as an adult in 1933, into the 3,600-gallon tank.
Now they want the mottled gray-green, 22-pound, 42-inch-long fish to mate, even though they aren’t sure if it’s a male or female-or if at its advanced age mating is possible. (The only time the lungfish seemed to be in the mood in its 60 years at the aquarium was in 1975, according to keepers.)
So now they plan to add three to five more lungfish-males and females-by early 1994 to create a sort of lungfish honeymoon suite. With that in mind, they outfitted the tank with stuff they think will get the fish romantic.
Mirrors. Special lighting. A gadget that will splash them with lots of cold water.
Lungfish really like that. It gets their hormones racing, ending up, according to one researcher, with “quite complex, noisy breathing and pursuing rituals.”
If the Shedd succeeds, it will be the first aquarium in the world to have bred the species, a living relic that breathes with a lung and has not evolved in 100 million years. The lungfish’s very existence is cited by scientists as proof that Australia, Africa and South America once were one massive continent.
Only 19 of the rare, endangered fish live in American aquariums. Sluggish by nature, slimy to the touch, they have a small but devoted core of human admirers who find the Australian lungfish among the most intriguing and anomolous animals in the world.
Scientists who study lungfish for clues to everything from evolution to plate tectonics will be especially pleased if the fish breed in Chicago.
“Fishes are the first vertebrates, and (Australian lungfishes) are primitive vertebrates,” said Dr. John Wourms, a Clemson University zoologist who specializes in evolutionary development. He travels often to Australia to study lungfish.
“If you are interested at getting at the root of things, you look at fishes,” Wourms said. “It would be nice to have breeding pairs in this country. It would be a lot cheaper going to Chicago instead of Australia to get eggs.”
Lungfish are a relic species. Like other fishes, lungfish get their oxygen by passing water through their gills. But lungfish also ocassionally rise to the surface and use their lungs by breathing through their mouths, making them akin to amphibians.
Breathing lungfish long have sent scientists scurrying to figure out how they are related to the first amphibians that crawled onto land to begin evolving into mammals and, eventually, into humans.
In aquarium lore, late at night in darkened, otherwise silent galleries, the ethereal sigh of a lungfish supposedly has sent unknowing nightwatchmen scurrying too.
The lungfish first appeared about 400 million years ago, and six kinds live in small numbers in hot, turbid, isolated rivers in Africa, South America and Australia.
The wide distribution of the fish is cited by many as proof of the now widely accepted theory that all three continents once were a land mass that scientists call Gondwanaland.
Fossils show identical freshwater lungfish living on all three continents before continental drift began to separate Gondwanaland 150 million years ago. In the millenia since, four distinct species evolved in Africa, one in South America and one in Australia.
Those in Africa and South America evolved more highly, developing two lungs and the ability to become dormant drought dries up their streams. African lungfish can live out of water in a dry mud cocoon for up to four years.
The less highly evolved Australian lungfish, with one lung, would die in such conditions. It is identical skeletally to fossils found of the fish that lived 100 million years ago.
But, the Australian version, during dry seasons when many are isolated in tiny brackish pools, survive while all other fish species in the pool die of lack of oxygen in the water. The reason: Lungfish can continue to get oxygen by surfacing to breath through their mouths.
Lungfish preceded dinosaurs, lived with them, probably were eaten by them and survived when the dinosaurs lumbered into extinction 63 million years ago.
With that record of longevity, the possibility that lungfish will become extinct because of human proliferation is enough impetus to study them and to try to breed them.
The Shedd is going to try breeding them in its new exhibit constructed especially for that purpose.
It is a meticulous re-creation of a muddy, 14-foot stretch of Australia’s Brisbane River, where wild lungfish live. The exhibit’s riverbank is graced with real eucalyptus trees, shrubs and, most importantly, grasses that grow into the water.
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In nature, fertilized lungfish eggs attach to underwater grasses until they hatch. The Shedd hopes its colony will get the hint and start dropping and fertilizing eggs in its exhibit.
Nobody knows exactly what turns on the Australian lungfish’s procreation drive. Scientists have been studying them intensively in the wild only in recent years.
Females seem to ovulate during the Australian spring, beginning in October. It is the only time females become visually distinct from males, as the females become gravid, swollen with unfertilized eggs. It is an event probably triggered by increasingly earlier sunrises.
Spring rains also seem to be a trigger. Scientists believe the rain cools the water in the subtropical rivers where they live, while dramatically diluting the water’s normal high alkaline content.
Dr. Jean Joss, one of Australia’s leading lungfish authorities, in a paper delivered to a lungfish symposium in Cleveland two years ago outlined what happens next:
“Most of the field observations describe quite complex, noisy breathing and pursuing rituals, followed by the fish intertwining, lying on their sides, the eggs being deposited singly or in pairs, and the male fertilizing each as it emerges.”
In other words, the lungfish become amorous when the lights are turned on early and when cold, pure water is poured on them.
And that is what the Shedd exhibit will do, essentially, with its water system independent of all others, hooked to a distilling machine and a chiller.
The design staff also added underwater mirrors on either end of the exhibit. They did so partly to give the people the illusion of a continuous river. But breeding experts think mirrors give fish the illusion that they are among larger numbers of their own kind, and that may stimulate breeding.
“It will be an event when zoologists get lungfish to spawn in this country,” said Dr. James W. Atz, curator emeritus at the American Museum of Natural History in New York.
William Braker, director of the Shedd who retires as of Dec. 31, will go to Australia to accompany the lungfish that Queensland is donating to the aquarium. Rare and endangered, the species is closely protected by the government, which seldom allows specimens to leave Australia.
Once they’re here, Roger Klocek, the Shedd’s fish curator, will oversee the attempt to breed them.
“You cannot tell a male from a female except at spawning time,” Klocek said, “so we won’t know what we’re getting when the fish arrive from Australia. But with three to five of them, chances are pretty good that we’ll have some of each sex.”
A freakish accident at the Shedd in 1975 may have triggered the only known attempt by its resident lungfish to mate. And, had Shedd keepers known then what they know now, it might today have colonies of captive-bred lungfish.
At that time, the aquarium’s surviving lungfish was with its mate; the two came here together in 1933. In 42 years together, they had shown no mating inclination.
During a renovation project at the aquarium in February 1975, concrete being poured by outside contractors seeped through a faulty seal and spilled into a 55,000-gallon freshwater reservoir.
All exhibits linked to the reservoir immediately became turbid with liquified concrete, raising the alkaline content of the water to dangerously high levels.
Klocek said he and other keepers took emergency measures, flooding the tanks with cold, fresh water, which suddenly dropped tank temperatures by 15 degrees. And they gradually cut back the water’s alkaline content by adding hydrochloric acid.
Their efforts worked, and all but 11 fish from all the exhibits survived unscathed, including the two lungfish.
Unwittingly, their emergency measures perfectly matched what are now believed to be the mating stimuli of the lungfish. The keepers were astonished three months later to find hundreds of lungfish eggs released in the tank one morning.
The eggs were unfertilized, however, and nothing came of the isolated mating attempt. The second fish died in 1982.
“We still have no idea if either of the fish was a male,” said Klocek, “or if both of them were females and both carried eggs.”
Now that the aquarium is armed with more knowledge and better equipment, Klocek believes it is ready to succeed.