Genetically modified ‘neon’ fish invades rivers in MG – 03/10/2023 – Environment

A small aquarium fish genetically modified to acquire a fluorescent red or green hue is slowly invading the streams in the Muriaé region, in the interior of Minas Gerais.

The transgenic variety of paulistinha (danio rerio), a very popular species among aquarists, has already shown itself capable of consuming food resources in the region’s waters and reaching sexual maturity right there, which could end up being bad news for native fish.

The study on the presence of transgenic paulistinha in the streams of Muriaé was coordinated by André Lincoln Barroso Magalhães, from the Federal University of São João Del Rei.

“In terms of biological invasions, anything is possible”, sums up Magalhães, when commenting on the risks of the animal’s arrival in freshwater ecosystems in Brazil.

“We didn’t find fry [filhotes] in streams, which means that this fish is at the beginning of the invasion process. But just the fact that they are preying on the microflora and microfauna in that environment is already quite worrying,” he said. Sheet.

The arrival of genetically modified fish is part of a broader problem in the region. Muriaé is a breeding center for ornamental fish, many of which are exotic species. This is the case of the paulistinhas —despite the popular name, they are native to India and neighboring Asian countries. They only gained the nickname because of their stripes, which resemble the flag of the state of São Paulo.

The fish breeding tanks are very close to the streams, and usually there are no measures to prevent the animals from escaping through the effluent pipes, for example. Therefore, it is common for exotic species to end up escaping.

“I’ve already collected streams that had 20 non-native species against three native”, says the researcher.

There is even a chance that so-called biotic differentiation will occur, with each stream acquiring different sets of invasive species over time.

Since the last decade, Brazilian legislation has prohibited the sale of fluorescent fish, known by the trade name GloFish, but producers and aquarium shop owners are often not aware of the ban, according to him.

In an article published in the scientific journal Studies on Neotropical Fauna and Environment, Magalhães and his colleagues map the presence of the transgenic form of paulistinha in five streams, among which two had more numerous populations of the animal.

In addition to analyzing the fish’s eating habits, the scientists also monitored their population dynamics and reproductive characteristics. They found that they are reaching maturity at a modest size, which can be a sign of rapid development.

Males and females are present in similar proportions in the population. The females are producing eggs, and both sexes reach the peak of development of their reproductive organs in the rainy season, which matches the natural pattern of the species. That is, in theory, there are conditions for the species to be able to reproduce in the streams of Muriaé.

In addition to the competition with native fish for food resources, the presence of transgenic paulistinhas is also a concern due to the aggressiveness of the species, which has the habit of chasing other fish.

“It costs nothing for them to do this with native lambari species, for example”, says Magalhães.

Genetic modification, by itself, does not necessarily increase the risk of invasive species, at least in this case. As the paulistinha has no close relatives in the rivers of Brazil, it is practically impossible for its “brilliant” genes (from marine invertebrates, such as a type of coral) to be inserted into native populations.

However, there are also already forms of GloFish that are black tetras (Gymnocorymbus ternetzi), fish typical of the Pantanal.

“We still don’t have the introduction of this modified tetra here, but it is something very worrying, especially if it happens close to the natural distribution of the species”, says the scientist.