‘Slender’ creature with ‘large’ head found in Mexico river. It’s a new species
In a pebbly river of southern Mexico, a “slender” creature with a yellow tail swam through the water. Its silvery-gray eyes scanned its surroundings, but it wasn’t the only one looking around.
Passing scientists noticed the brown animal — and discovered a new species.
A team of researchers spent 20 years visiting streams and rivers of Chiapas State as part of a project to survey aquatic biodiversity, according to a study published Aug. 4 in the peer-reviewed journal Neotropical Ichthyology.
During the searches, researchers collected over 100 fish which, they realized after taking a closer look, “did not correspond to any other described species,” the study said. They’d discovered a new species: Profundulus hectori, or Hector’s killifish.
Hector’s killifish have “slender,” roughly “cylindrical” bodies reaching nearly 3.5 inches in length, the study said. Their heads are “large” and “compressed.”
Photos show the “brown-orange” coloring of the new species. Its tail is yellowish, and its sides have a “dark band” of spotted scales, researchers said.
Hector’s killifish were found in freshwater rivers, streams and sometimes near waterfalls, where the ground was “composed of pebbles, sand and Sabino (tree) roots,” the study said.
Much about the lifestyle, diet and behavior of the new species remains unknown.
Researchers said they named the new species “after our friend and colleague” the late Hector Espinosa Perez, a Mexican ichthyologist, “in recognition of his many contributions to the study and conservation of freshwater fishes in Mexico.”
So far, Hector’s killifish has been found at over a dozen sites in Chiapas, a state of southern Mexico bordering Guatemala and the Pacific Ocean.
The new species was identified by its head shape, coloring, body proportions, scale arrangement and other subtle physical features. DNA analysis found the new species had at least about 4% genetic divergence from related fish species.
The research team included Sara Elizabeth Domínguez-Cisneros, Ernesto Velázquez-Velázquez, Omar Domínguez-Domínguez and Rosa Gabriela Beltrán-López.
This story was originally published August 8, 2025 at 6:28 AM with the headline "‘Slender’ creature with ‘large’ head found in Mexico river. It’s a new species."
