Researchers recently conducted an extensive survey in the Brazilian Amazon to study annual rivulids, a family of fish known for their remarkable ability to survive droughts by entering a dormant state and hatching when it rains—earning them the nickname “fish from the clouds.”
Brazil is home to around 200 species of annual rivulids, nearly half of which are at risk of extinction due to the vulnerability of their habitats—ponds, swamps, and marshes—to infrastructure projects such as highways, ports, and hydroelectric dams.
These species are not well-studied in the Amazon, but human activities are placing them under significant stress. The survey discovered three new endemic species in the area affected by the Belo Monte hydropower dam. While environmental licensing laws could help protect these fish, proposed legislation in the Senate threatens to weaken these crucial protections.
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Amazonian expedition searches out rare ‘fish from the clouds’
Transcript
Notice: Transcripts are machine and human generated and lightly edited for accuracy. They may contain errors.We caught a fish that I had never caught before. The first time I caught it, which is a Trigonects, it’s a new species of Trigonects, look at the size of this annual fish. By Amazon standards, it’s a big fish, right? A pretty big annual fish.
(André speaking) We are looking for fish from the Rivulidae family, which is a family of fish that occurs throughout the Americas. We are specifically looking for annual fish.
(André speaking) These are fish that have a very interesting ability to interrupt their development at a certain moment when the embryo is formed. From that moment on, the metabolism of these little fish goes into dormancy.
(Leandro speaking) And they will stay dry for a few months, in this dry vegetation layer that will protect the eggs from complete dehydration as well.
(Leandro speaking) and in a few months when it starts raining again, the eggs will rehydrate, complete the embryonic development process, hatch, and the fish will have a few months to grow and then they will be able to reproduce again.
(André speaking) and then deposit their eggs in their substrate until the pool dries up again. These adults will die, and it’s only in the next rainy season that we’ll have new fish born.
(Marcio speaking) The species we’ve identified has a characteristic reddish heart with golden spots, a very beautiful creature, so there are characteristics that suggest it could be a new species for us.
(Leandro speaking) So, we collected in this location here, you can see that it’s an area with a lot of mud.
(Leandro speaking) the river dries up, and it becomes an environment that looks like a mangrove. But here it’s freshwater. And we managed to collect some interesting species, one of them is a new species, Melanorrivulus, it’s a species we’re still going to describe.
(Leandro speaking) this group of fish is very interesting; they have a cool adaptation. When the puddle dries up, they start jumping in the foliage until they find another puddle or even go to the river. So whenever we collect them, they jump out of the net.
(Leandro speaking) and sometimes we have to chase them and catch them on the ground as they quickly move towards another puddle.
(Marcio speaking) this alcohol will preserve the fish tissues for future analysis, so we have to individually catalog each of these specimens from each of the species collected today.
(André speaking) we add as much metadata as possible to the material in general so that other people can access the information from these collection events we are participating in, and then we help researchers from around the world answer various questions, which allows us to use it for DNA studies and other molecules, among other uses.
(Marcio speaking) The addition of new records will allow researchers to better understand the species’ distribution and establish effective measures for its conservation.
(Leandro speaking) The main impact? The main threat to these species is the loss or transformation of their natural habitat into another type of environment.
(Marcio speaking) Here, in this example, we’re talking about pasture.
(Marcio speaking) in the background, we also have a pond area. So, sometimes, to provide water for the animals, farmers, landowners, tend to dig these more flooded areas to make them a bit deeper and store water for the cattle to drink.
But for the species we are studying, the annual killifish, they need this cycle of filling and drying in this environment.
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