A marine worm with colors similar to a jaguar’s fur and never before recorded by science was discovered at Playa Naranjo, within Santa Rosa National Park in Guanacaste.

The new species was given the scientific name Sthenelais onca and is part of a discovery made by researchers from the BioMar-ACG project, led by the Center for Research in Marine Sciences and Limnology (Cimar), the Guanacaste Conservation Area (ACG), and Minae.

“The analyses confirmed that this was a species completely new to science,” the scientific team explained.

In addition, the study was published on April 24 in the international journal ZooKeys.

The discovery began nearly a decade ago The first encounter with this species occurred in February 2016 during a scientific expedition to Playa Naranjo.

On that occasion, researchers collected four specimens buried in the wet sand of the intertidal zone.

However, it wasn’t until May 2024 that a new expedition allowed them to obtain more specimens and complete the scientific analysis.

University students and local parataxonomists associated with the BioMar-ACG project also participated in the work.

A worm inspired by the jaguar

The new species caught the researchers’ attention due to several unusual characteristics.

As the team explained, the worm features orange, gray, and cream tones reminiscent of the jaguar’s (Panthera onca) fur.

“Precisely because of that resemblance and because it is a predator within the marine ecosystem, it was named Sthenelais onca,” noted the ACG.

In addition, the specimen can grow up to 11 centimeters in length, making it one of the largest recorded in this type of sandy environment.

Scientists also identified unique structures known as smooth setae and a distinctive notch in the scales covering the front of the body.

The research included genetic analysis

To confirm that this was a previously undescribed species, the team conducted detailed morphological analyses, created scientific illustrations, and performed genetic studies.

In addition, the researchers used phylogenetic analysis to compare this marine worm with species recorded in different parts of the world.

The results showed that the specimen found at Playa Naranjo did not match any previously documented species.

Subsequently, the specimens were added to the Annelida scientific collection at the Zoology Museum of the University of Costa Rica.

At the same time, the genetic sequences obtained were incorporated into international scientific reference platforms.

Costa Rica Continues to Uncover Unknown Species

The discovery reaffirms the Guanacaste Conservation Area as one of the most important sites for marine biodiversity research in Costa Rica.

It also highlights how much remains to be learned about the species inhabiting the marine ecosystems of the Costa Rican Pacific.

Since 2015, the BioMar-ACG project has been conducting research to document the marine biodiversity present in the ACG’s protected areas.

“This project aims to document, study, and disseminate information on the marine biodiversity present in the ACG’s protected areas,” the experts noted.

Meanwhile, researchers continue to generate genetic and scientific data on marine species found in Costa Rica.

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