It seems incredible that in the 21st century we're still encountering biological surprises of this magnitude in inland waters, but nature always has a trick up its sleeve. Recently, the scientific world has turned its attention to South America after the confirmation of an unexpected visitor in Paraguay that has left more than one person speechless: the first freshwater jellyfish officially recorded in the country.
The researcher responsible for this discovery is Romina Melissa González de Dos Santos, affiliated with the Faculty of Exact and Natural Sciences (FACEN-UNA), who has carried out impeccable fieldwork. Thanks to her perseverance, what many locals already suspected based on previous sightings, but which until now lacked the necessary scientific backing to be included in national biology textbooks, has been academically documented.
What animal exactly is Craspedacusta sowerbii?
We're not talking about just any old jellyfish that ruins our swim in the Mediterranean, but a translucent hydrozoan that barely reaches the size of a two-euro coin. This species, scientifically known as Craspedacusta sowerbii , is native to the Yangtze River in China, but it has proven to have a very active passport, having colonized almost every continent except Antarctica, adapting to a wide variety of climates.
Physically, it is a fascinating creature with a bell-shaped body that is whitish or greenish and becomes almost invisible underwater. Despite its small size, which ranges from 20 to 25 millimeters, it has up to four hundred tentacles arranged along the edge of its bell, which it uses both to maintain its position in the water column and to capture its daily food.
The scene of the discovery: a quarry with history
The sighting occurred not in a natural lake, but in an old quarry located in Ypacaraà that accidentally filled with water in the 70s after an underground vein was drilled. In this environment of calm, confined waters, the researcher and her team, navigating in kayaks, managed to collect six jellyfish-stage specimens for later analysis in the university laboratory.
The curious thing is that, according to local residents, these little intruders have been seen there for over a decade, but no one had ever bothered to investigate what they were doing in a closed lagoon. Some even speculate about people who introduced species de peces exotic years ago, this could have served as accidental transport for jellyfish in their earliest stages.
How did an Asian species arrive in Paraguay?
The big question everyone is asking is how a creature from China ends up in an isolated quarry in the middle of South America. Experts point directly to human activity as the main means of dispersal, since these jellyfish possess structures called podocysts, which are like microscopic capsules of resistance capable of sticking to boots, wetsuits, or boat hulls for a very long time.
It only takes someone using their diving equipment or a small boat in an infested area and then going to the Ypacaraà quarry for the invasion to begin. This ability to remain dormant until it finds the ideal conditions is what makes them so dangerous from an ecological standpoint, as they are capable of crossing borders without raising the slightest suspicion.
Environmental impact and potential risks to humans
Although these jellyfish have traditionally been thought of as harmless, recent studies have raised concerns by detecting toxins that could cause inflammatory skin reactions. While it's not cause for immediate alarm, there is at least one documented case of a person experiencing skin damage after contact, so it's wise to be cautious if you encounter them during a recreational swim.
From an ecological perspective, the concern is more serious because these animals feed on zooplankton, the same food source that the young of many local fish need to survive. If the jellyfish population grows unchecked, they could deprive native species of food, completely disrupting the food chain of these delicate and closed aquatic ecosystems.
This scientific discovery not only puts an end to years of rumors among the local population, but also compels institutions to take the control of exotic species in the country's waters more seriously. The identification of Craspedacusta sowerbii in this quarry is a clear sign that biodiversity is changing and that it is essential to continue monitoring these environments to understand how new inhabitants interact with native fauna, thus preventing a curious anecdote from becoming a difficult-to-solve environmental problem in the near future.