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Mysterious creatures in the river: Why did pufferfish evolve into freshwater dolphins?
Dolphins in rivers are not only a peculiar display of aquatic life, they are also a fascinating example of evolution in action. The uniqueness of these creatures and their relationship to the ocean’s dolphins takes us on a journey into the past and understanding nature.
River dolphins are a polyphyletic group of fully aquatic mammals that live primarily in fresh or salt water.
When we think of dolphins, we usually picture graceful sea creatures, but river dolphins are something else. Among these freshwater creatures, there are five extant species, including the South Asian dolphin, the Amazon River dolphin, and others. They are smaller than their marine counterparts and usually live in warm, shallow, fast-flowing rivers, feeding mainly on fish.
These creatures have specialized external structures, such as long snouts and conical teeth, which facilitate their capture of smaller prey.
The evolution of river dolphins can be traced back to about 40 million years ago, when their ancestors were land animals. After entering the aquatic environment, these species gradually developed a series of characteristics adapted to life in water. Their ears are significantly different from those of ordinary land mammals and are better at receiving sounds in water.
Interestingly, visibility in shallow water is often very low, so these creatures do not rely on their eyesight, but instead rely on echolocation to hunt and navigate. This allows river dolphins to search for prey flexibly in turbid water.
Studies show that these dolphins rely so heavily on echolocation that they can survive even without their eyesight.
River dolphins face many threats, particularly habitat destruction caused by human activities. Around 2006, the Yangtze River dolphin was declared functionally extinct, a clear reminder of the fragility of the ecosystem and the impact of human behavior.
With the growing human population and economic activity in water bodies, the expansion of agriculture and industry has made survival increasingly difficult for these animals. Habitat destruction and reduced fish stocks in rivers further threaten these rare species.
In the Amazon River basin, human fishing activities have formed a direct competition with the survival of river dolphins, causing these dolphins to face increasing survival pressure.
Despite this, conservation efforts continue around the world. In 2023, nine countries signed the Global River Dolphin Declaration, hoping to improve the conservation status of river dolphins and promote research through international cooperation. This marks a new era with greater attention paid to biodiversity and ecosystem balance.
The signing of this declaration not only strengthens cooperation among countries, but also symbolizes people's attention to protecting these mysterious creatures.
With habitat loss, fish shortages and human impacts on the natural environment, the future of river dolphins is challenging. In such a crisis-ridden era, protecting these unique creatures should be a top priority for all countries.
Will the true stories of the mysterious creatures in the river be forgotten as their species disappear?
