Eupera troglobia is the first fully described cave-dwelling clam species discovered in the Americas, and possibly the second in the world.
Eupera is a genus of bivalve mollusks in the family Sphaeriidae relatively widespread throughout South America.
These mollusks are normally found in the roots of water hyacinth, an aquatic plant that floats in calm freshwater environments.
A total of 11 scientifically recognized Eupera species occur in South America east of the Andes, all of which have characteristic shell pigmentation with dark brown spots in a beige ground color.
“The typical troglobitic (cave-dwelling) mollusk usually exhibits the following characteristics: (i) absent or reduced pigmentation, (ii) absent or reduced eyes, (ii) some reduction in shell size,” said Dr. Rodrigo Lopes Ferreira from the Federal University of Lavras and Dr. Luiz Ricardo Simone from the Museum of Zoology of the University of São Paulo.
“Bivalves have eyes in only a few lineages, the Sphaeriidae are not among them, so the absence of eyes in Eupera cannot be considered.”
“However, small bivalves from Casa de Pedra Cave in the central region of Brazil have the other characteristics to be classified as a troglobite: absence of pigment, fragile shell, and small size.”
The first records of Eupera troglobia appeared in a 2006 technical report of Brazil’s National Center for Cave Exploration and Conservation.
In that report, a faunal survey of Casa de Pedra Cave was presented, focusing on invertebrates. Although the author presented some photographs of the clam, little attention was paid to it, which was thought to have been carried into the cave by the water.
In 2010, Dr. Lopes Ferreira accessed the report and considered the possibility that clam might be a cave-dwelling species due to its depigmentation.
He searched for sampled specimens but was unable to find any in the collection where the remaining specimens were deposited, suggesting that specimens were not collected on this occasion.
In 2021, Dr. Lopes Ferreira and Dr. Ricardo Simone visited Casa de Pedra Cave specifically to search for such shells.
Although the cave was partially flooded, the researchers were able to find specimens and described them in a paper in the journal Subterranean Biology.
“All known South American species of Eupera have well-defined dark spots in the central region of the valves, contrasting with the light brown background,” they said.
“Eupera troglobia is the only species that lacks these dark spots and has a shell of uniform pale yellow color, slightly distinguishing the new species from its relatives.”
“Our discovery is the latest reminder about how important the conservation of the fragile subterranean habitats is, given the treasure troves in their holdings,” they concluded.
“Meanwhile, recently amended laws in Brazil put caves at considerably higher risk.”
L.R.L. Simone & R.L. Ferreira. 2022. Eupera troglobia sp. nov.: the first troglobitic bivalve from the Americas (Mollusca, Bivalvia, Sphaeriidae). Subterranean Biology 42: 165-184; doi: 10.3897/subtbiol.42.78074
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