Aquarium surprised by shark born in a tank without males
The Shreveport Aquarium in Louisiana kicked off 2025 with a mysterious birth. A swell shark (Cephaloscyllium ventriosum) pup hatched at the facility on January 3, yet the two female sharks present in the tank have not been in contact with a male in over three years. The team at the aquarium suspects the birth could be delayed fertilization or a rare reproductive phenomenon called parthenogenesis.
Parthenogenesis is a reproductive strategy where primarily female sex cells called gametes can develop without fertilization. It is commonly seen in plants and some invertebrate animals (including aphids, ants, wasps, and bees). However, some higher vertebrates–like sharks, snakes, and some birds–may reproduce this way from time to time. In sharks, it is usually reserved as a last resort if there aren't any mates to go around.
According to the aquarium, the shark egg was first spotted eight months ago. The shark hatched a few weeks ago and the team at the aquarium is working to determine how it was conceived. Once the shark is big enough for a blood draw, DNA analysis should provide answers in the next few months. If not parthenogenesis, it could have been born via delayed fertilization. In sharks, this is when a female will store some sperm cells from previous encounters to use on future eggs.
'This situation is incredible and shows the resilience of this species,' Greg Barrick, the Curator of Live Animals at Shreveport Aquarium, said in a statement. 'We are very excited in the coming months to confirm whether this was indeed a case of parthenogenesis or if it was delayed fertilization.'
In the wild, swell sharks are found in coastal waters of the eastern Pacific Ocean. They have spots along their scales and can grow up to three feet long. Swell sharks are best known for their ability to swell their bodies with water or air as a way to deter predators. The new swell shark is nicknamed Yoko after the Chumash word for shark (onyok).
Yoko is currently doing well, but young sharks born during rare reproductive events do face some significant challenges. Offspring born from parthenogenesis often die young, yet scientists are still not sure why. They suspect the expression of a lethal recessive gene could kill the pups prematurely.
[ Related: A virgin birth in Shedd Aquarium's shark tank is baffling biologists. ]
'Should Yoko's time with us be brief, it will still leave an unforgettable legacy, contributing invaluable insights to the study of shark reproduction and conservation efforts,' the aquarium wrote.
Yoko is currently being closely monitored away from public view for its health and well-being.
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Miami Herald
6 days ago
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Yahoo
7 days ago
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Water flea population soared in South Side stretch of Chicago River after 2023 sewage release
In the summer of 2023, strange things happened to the tiny creatures that swim and float in the Chicago River. One type of water flea, Chydoridae, basically disappeared from the South Side stretch known as Bubbly Creek, while another, Moinidae, experienced a dramatic population surge. 'You could see them with your eyes — clouds of them were so thick,' Shedd Aquarium research biologist Austin Happel said of the Moinidae, each about the size of the tip of a gel pen. 'I've never seen that before in the wild.' The 'drastic' population shifts happened after the sewer system, overwhelmed by torrential rains, released 3 billion gallons of raw sewage and stormwater into the Chicago River, according to a recent study in the journal Knowledge and Management of Aquatic Ecosystems. About 2 billion gallons of that contaminated water was released into Bubbly Creek, where the authors of the study tracked tiny aquatic organisms known as zooplankton, including Moinidae and Chydoridae. 'I was surprised at the numbers and the drastic population level that the Moinidae reached — because that's really high,' said Happel, lead author of the study. In multiple samples, Moinidae was present at levels more than 50 times higher than normal, and in one case 450 times higher. 'You're drastically changing up what's in this part of the river, and in theory that's going to have all sorts of other effects,' Happel said. Despite the widespread use of raw sewage releases in U.S. waterways, the environmental effects aren't well studied or understood, Happel said. His study is one of the first to look at the effects on zooplankton, tiny organisms that are eaten by fish and insects and represent an important part of the food chain. Among the effects of the Bubbly Creek sewage release: Oxygen levels in the water went to almost zero as bacteria from human waste consumed oxygen and the waste broke down. Fish, which need oxygen in the water to survive, fled the area, perhaps abandoning their young, Happel said. In addition, untreated sewage commonly contains potentially hazardous compounds, such as pharmaceuticals, illicit drugs and biocides, a category including pesticides and antiseptics. The booming zooplankton population could have eaten those toxins, and when fish moved back to the area they would have eaten the zooplankton, potentially accumulating toxins. An angler, in turn, could have eaten the fish, Happel said. Another possibility is that when fish migrated out of the polluted waters, there were less fish in that area to eat mosquito larvae, leading to more mosquitoes. Without more study of how different species respond to sewage releases, we won't know what contaminants people might be exposed to, or what diseases might be spread by additional mosquitoes, Happel said. 'We might be missing something big (or) maybe the ecosystem's super resilient and we need to look at why is the system resilient,' he said. He and his colleagues are currently tracking other species in Bubbly Creek, named for the gas bubbles that used to emerge from decaying animal parts in the days when the waterway was used as a dumping ground for the Chicago stockyards. The researchers are monitoring turtles, herons, fish and insects, in both Bubbly Creek and other areas of the Chicago River. Those other areas could be used for comparison, should another big sewage release affect Bubbly Creek. Overall, sewage releases in the Chicago River are down, Happel said, because of the $4 billion Deep Tunnel project, an ongoing regional effort to prevent flooding by temporarily holding excess water in massive tunnels and vast reservoirs. Before 2017, sewage releases were happening each month, Happel said, but now we've gone almost two years since the last big release in 2023. 'The city's making tremendous progress,' he said. But even the Deep Tunnel is not enough to handle all of the overflow from severe storms that are occurring more often because of climate change. Chicagoans can help, according to the Shedd, by signing up for Overflow Action Alerts from the Metropolitan Water Reclamation District of Greater Chicago. During alerts, residents can reduce pressure on the sewer system — and help prevent flooding — by limiting showers, delaying running the dishwasher and avoiding doing laundry. Such efforts may feel too small to matter, Happel said, but, in this case, strength lies in numbers. 'If we could get a whole block of high-rises to abide by that, that could really reduce the pressure that's put on the system during those rain days,' he said. nschoenberg@
Chicago Tribune
13-06-2025
- Chicago Tribune
Water flea population soared in South Side stretch of Chicago River after 2023 sewage release
In the summer of 2023, strange things happened to the tiny creatures that swim and float in the Chicago River. One type of water flea, Chydoridae, basically disappeared from the South Side stretch known as Bubbly Creek, while another, Moinidae, experienced a dramatic population surge. 'You could see them with your eyes — clouds of them were so thick,' Shedd Aquarium research biologist Austin Happel said of the Moinidae, each about the size of the tip of a gel pen. 'I've never seen that before in the wild.' The 'drastic' population shifts happened after the sewer system, overwhelmed by torrential rains, released 3 billion gallons of raw sewage and stormwater into the Chicago River, according to a recent study in the journal Knowledge and Management of Aquatic Ecosystems. About 2 billion gallons of that contaminated water was released into Bubbly Creek, where the authors of the study tracked tiny aquatic organisms known as zooplankton, including Moinidae and Chydoridae. 'I was surprised at the numbers and the drastic population level that the Moinidae reached — because that's really high,' said Happel, lead author of the study. In multiple samples, Moinidae was present at levels more than 50 times higher than normal, and in one case 450 times higher. 'You're drastically changing up what's in this part of the river, and in theory that's going to have all sorts of other effects,' Happel said. Despite the widespread use of raw sewage releases in U.S. waterways, the environmental effects aren't well studied or understood, Happel said. His study is one of the first to look at the effects on zooplankton, tiny organisms that are eaten by fish and insects and represent an important part of the food chain. Among the effects of the Bubbly Creek sewage release: Oxygen levels in the water went to almost zero as bacteria from human waste consumed oxygen and the waste broke down. Fish, which need oxygen in the water to survive, fled the area, perhaps abandoning their young, Happel said. In addition, untreated sewage commonly contains potentially hazardous compounds, such as pharmaceuticals, illicit drugs and biocides, a category including pesticides and antiseptics. The booming zooplankton population could have eaten those toxins, and when fish moved back to the area they would have eaten the zooplankton, potentially accumulating toxins. An angler, in turn, could have eaten the fish, Happel said. Another possibility is that when fish migrated out of the polluted waters, there were less fish in that area to eat mosquito larvae, leading to more mosquitoes. Without more study of how different species respond to sewage releases, we won't know what contaminants people might be exposed to, or what diseases might be spread by additional mosquitoes, Happel said. 'We might be missing something big (or) maybe the ecosystem's super resilient and we need to look at why is the system resilient,' he said. He and his colleagues are currently tracking other species in Bubbly Creek, named for the gas bubbles that used to emerge from decaying animal parts in the days when the waterway was used as a dumping ground for the Chicago stockyards. The researchers are monitoring turtles, herons, fish and insects, in both Bubbly Creek and other areas of the Chicago River. Those other areas could be used for comparison, should another big sewage release affect Bubbly Creek. Overall, sewage releases in the Chicago River are down, Happel said, because of the $4 billion Deep Tunnel project, an ongoing regional effort to prevent flooding by temporarily holding excess water in massive tunnels and vast reservoirs. Before 2017, sewage releases were happening each month, Happel said, but now we've gone almost two years since the last big release in 2023. 'The city's making tremendous progress,' he said. But even the Deep Tunnel is not enough to handle all of the overflow from severe storms that are occurring more often because of climate change. Chicagoans can help, according to the Shedd, by signing up for Overflow Action Alerts from the Metropolitan Water Reclamation District of Greater Chicago. During alerts, residents can reduce pressure on the sewer system — and help prevent flooding — by limiting showers, delaying running the dishwasher and avoiding doing laundry. Such efforts may feel too small to matter, Happel said, but, in this case, strength lies in numbers. 'If we could get a whole block of high-rises to abide by that, that could really reduce the pressure that's put on the system during those rain days,' he said.
