Gambusia affinis or mosquitofish is an invasive fish that chews off the tails of both freshwater fishes and tadpoles. They also dine on the amphibian's eggs and fishes, leaving the native animals to die prematurely. A recent study plans on turning the tide against invasive species by designing a robot to scare the mosquitofish. Authors report how the engineered robot alters the behavior, fertility, and physiology of the invasive fish.
Combating the Invasive Mosquitofish
HEMET, CA - APRIL 26: Mosquitofish are seen in a container at offices of the Riverside County Department of Environmental Health which gives them away for free to anyone who wants to use them to control mosquitoes on their property on April 26, 2007 in Hemet, California. California health officials announced this week that West Nile Virus season is starting earlier than usual because of an unusually warm March. Mosquitoes that carry the virus have begun breeding earlier than usual and the West Nile Virus has been detected in mosquito pools, birds, or horses in eight California counties. Although the virus has not been detected in humans so far this year, 24 people have died and 1,200 sickened by the virus over the past two years in California. West Nile can be transmitted from infected birds, squirrels, and other animals to humans and animals such as horses through several varieties of female mosquitoes. The disease first appeared in the United States in 1999 in New York and killed hundreds of people during its westward expansion before gaining a firm foothold in California in 2004. In reaction to the early start of West Nile Virus season, the California State Legislature this week declared April 23-29 "West Nile Virus and Mosquito and Vector Control Awareness Week". The effected counties include Imperial, Los Angeles, Orange, Riverside, Santa Clara, San Diego, Sonoma and Stanislaus.
To combat the mosquitofish, an international team of biologists and engineers from Italy, the US, and Australia turned to its natural predator, the largemouth bass, for inspiration. They created a robotic fish that mimics the appearance and effectively simulates the real predator's movements.
Aided by computer vision, the engineered robot strikes when it perceives mosquitofish approaching tadpoles of an Australian species, which is threatened by the invasive species in the wild. Scared and stressed, the invasive mosquitofish showed fearful behavior and was seen to experience weight loss changes in its shape and a reduction in fertility that impaired the mosquitofish's survival and reproduction.
Giovanni Polverino, the first author of the study from the University of Western Australia, explains that mosquitofish are one of the 100 world's worst invasive species, with current eradication methods being too expensive and time-consuming to contrast the species spread. He adds that the global pest is a grave threat to many aquatic animals. Instead of killing the mosquitofish one by one, the team presents an approach that can inform better strategies to control the pest. The team brought the mosquitofish's worst nightmare into reality through the robot fish that scares it but not the other aquatic animals around it, reports PhysOrg.
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Mimic Mosquitofish's Robot Predator Saves Freshwater Fish and Tadpoles
In the study published in the journal iScience, titled "Ecology of fear in highly invasive fish revealed by robots," authors elaborate how in the presence of the engineered robotic predator, the mosquitofish tended to stay close to each other and spend more time at the center of the testing area hesitant to tread in uncharted waters. The invasive species also swam frenetically, with frequency sharp turns than those who hadn't met the robotic predator. Away from the robot and back in their home, the effects of fear lasted. The fish were less active, ate more, froze longer, and were presenting signs of anxiety that continued for weeks after their last robotic encounter.
For the tadpoles that the mosquitofish typically preyed on, the presence of the robot changes the norm for the better. While mosquitofish is a visual animal that keeps surveying its environment mainly through its eyes, tadpoles have poor eyesight and don't see the robot well. Polverino explains that the team expected the robot to have a neutral effect on the tadpoles, but it wasn't the case. Because the robotic predator changes the mosquitofish' behavior, the tadpoles didn't have predators at their tails and were more willing to venture out of the testing arena. He adds that it turned out to be a positive thing for the tadpoles. Once freed from the lurking danger of the mosquitofish around, they were no longer scared.
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