âRemarkably, our team found that Antarctic fish compensate for increasing metabolic demands by improving respiration through species-specific locomotor and respiratory responses, demonstrating resilience to environmental change and possibly global warming,â said said Friedlander, who is also director of the Fralin Biomedical Research Institute. director.
âAmbient warming presents a multi-faceted challenge for fish, including an increase in the temperature of the central nervous system and target tissues such as skeletal and heart muscles, but also reduced availability of dissolved oxygen in water. that passes through the gills during respiration. these results suggest that Antarctic fish may be able to adapt somewhat behaviorally under extreme conditions, little is known about the effects of environmental warming on their predation habits, food availability and fertility, âFriedlander said.
Iskander Ismailov, the study’s first author and assistant research professor at Friedlander’s lab during the study, said: âThe behavioral manifestations we have described show that these fish have powerful physiological abilities to survive environmental changes.
Thanks to millions of years of isolation from the rest of the world – encircled by the Antarctic Circumpolar Current – fish species in the Southern Ocean have adapted well to their icy ecosystem.
Blackfin icefish, Chaenocephalus aceratus, one of two species studied by the team, has unique opalescent blood. These fish are among the few known vertebrates lacking in hemoglobin, a molecule in red blood cells that efficiently carries oxygen from the lungs of terrestrial vertebrates, or the gills of aquatic vertebrates, through the tissues of the body. Instead, the blackfin icefish carry dissolved oxygen in blood plasma, housing about 10% of hemoglobin’s oxygen carrying capacity.
Oxygen is more soluble in cold water, allowing ice-whitefish to thrive in the Southern Ocean. However, as the water temperature increases, these species experience increased metabolic demand, potentially making white-blooded fish more vulnerable to global warming. To test this hypothesis, the team examined five specimens of white-blooded blackfin icefish and five red-blooded black cod, Notothenia coriiceps, in a climate-controlled coastal laboratory that gradually circulated and heated salt water directly from the Southern Ocean.
The fish acclimatized to laboratory conditions, before being transferred to the experimental tank, where the water temperature rose from -1.8 degrees Celsius to 13 degrees, at a rate of 3 degrees per hour. The researchers captured numerous video recordings, allowing them to examine and quantify the motility, respiratory rate, tank maneuvers and fin movements of the fish.
As the water temperature rose, the white-blooded icefish exhibited intensive pectoral fin venting – a behavior previously seen in icefish during egg protection – which the researchers said could help facilitate breathing. In contrast, red-blooded fish have used complex maneuvers, including fanning and spreading the pectoral fins, followed by startle-like C-bends, which can increase gill ventilation, according to Ismailov.
“The results offer a new perspective on the effects of rising temperatures on these very cold-adapted species,” said George Somero, professor emeritus of marine biology at Stanford University and a leader in the study of how marine life adapts to heat stress, which was not involved in the study.
Preparation for the expedition began in early 2014. The research team designed, custom-built and shipped laboratory equipment to Palmer Station in Antarctica before living there for three months in 2015. The trip included a flight. towards Punta Arenas, in Chile, then a crossing of the Drake Passage by boat during the austral autumn.
Ismailov was the first to arrive, setting up experimental platforms. Six weeks later, he was joined by Jordan Scharping, then a sophomore at Virginia Tech Carilion School of Medicine conducting research in Friedlander’s lab. The pair worked in overlapping 12-hour shifts to conduct laboratory experiments at near-freezing temperatures.