Fish and Adaptation: Mangrove Fish Jumps into Air in Warming Water

Various creatures have their flexibilities and coping methods for change, as we know. Some are more unusual than others: In humid heat in tropical mangroves, tiny rivulus fish actually jump out of the water in order to cool off, says a new study from the University of Guelph.

The researchers said that the fish, Kryptolebias marmoratus, lowered their body temperatures by chilling themselves in the air.  Also, later, when they were more accustomed to the heat after having experienced higher temperatures for a week, they coped better with warm water, according to a release.

Before that happens, though, jumping is important to the fish in leaving behind rising temperatures for a bit, said Pat Wright, lead author on the study and integrative biology professor at University of Guelph, in the release. "If the fish are prevented from jumping out of the water, they would die."

These innovative fish live in warm waters from Brazil to Florida, where temperatures in the water can reach 38 Celsius, one degree above normal human body temperature.

In the stdy, undergraduate students Emma Sylvester and Dan Gibson and other researchers captured the fish's actions using a camera that tracks body temperature. In warming water, fish hurled themselves out of the water and onto moist filter paper. There, they cooled nearly right away. After one minute, the fish body temperatures were below that of the filter paper.
In the mangroves, the fish wriggle to a spot on land and can get past barriers, too, a release noted.

"As climate change continues, and temperatures in their habitats continue to increase, we could potentially see them jumping more," Wright said in the release.

The team also analyzed the fish's plasticity, which is its ability to adjust to temperature increases, confirmed the release.

The study was recently published in the journal Physiological and Biochemical Zoology.

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