Blind Cave Shrimp Lost for a Century Rediscovered in Libya’s Underground Lakes

Deep beneath the city of Benghazi in northeastern Libya, a pale, eyeless shrimp that scientists feared might have vanished forever has quietly survived. Typhlocaris lethaea, a blind cave-dwelling prawn first described in 1920 from the mysterious Lethe cave, has been confirmed alive nearly a century after its original discovery, and it has turned up somewhere entirely unexpected. Field surveys conducted in 2023 and 2024 revealed the species in two caves of the Al-Coeffiah area northeast of the city, extending its known range by nine kilometers and suggesting that the subterranean waters beneath the Benghazi Plain form a far more connected and biologically rich network than anyone had realized.

The story of this species begins with an accidental observation. Vito Zanan was the first person ever to notice the decapod in the Lethe cave, also known as Al Jekh, and he sent specimens to the Italian zoologist Bruno Parisi. Parisi initially attributed the animal to Typhlocaris galilea, a related species from the Tabgha spring in the eastern Mediterranean, but after forwarding one specimen to William Thomas Calman at the British Museum, careful comparison with the type material of T. galilea revealed that the Libyan shrimp was something distinct. Parisi formally described it in 1920 as Typhlocaris lethaea, and then, remarkably, the trail went cold. The species was never reported again in the scientific literature, and even a recent molecular revision of the entire genus failed to obtain a single specimen. Faced with a complete absence of data, the International Union for Conservation of Nature classified T. lethaea as data-deficient, a category that left open the uncomfortable possibility that the species had already slipped into extinction.

The genus Typhlocaris itself is one of the Mediterranean region’s most enigmatic lineages of stygobiotic crustaceans, meaning organisms adapted exclusively to life in groundwater. All known species display classic stygomorphism: they lack eyes entirely and carry no body pigmentation, adaptations to a world of perpetual darkness. They are also distinguished by a longitudinal post-antennal suture running along the lateral surfaces of the carapace, a structural feature that helps taxonomists separate them from other decapods. Only four valid species are known, each confined to a single location around the Mediterranean with no representatives in the open sea. Typhlocaris galilea inhabits the Tabgha spring, while T. ayyaloni was discovered in the vast Ayyalon cave network roughly 120 kilometers to the south in Israel. Typhlocaris salentina lives in the Zinzulusa cave of southern Italy and has since been found in two additional caves. Until now, T. lethaea remained the sole member known from the southern shore of the Mediterranean, making it Benghazi’s only endemic cave species.

The rediscovery owes much to speleological exploration. The Lethe cave, located in the Bou-Atni area south of Benghazi at an altitude of 30 meters above sea level, was surveyed in 2007 and 2009 by a research group from the Centro Ibleo di Ricerche Speleo-Idrogeologiche di Ragusa in Italy together with the Earth Science Department at the University of Benghazi. The cave forms part of a line of collapsed dolines aligned in a northeast to southwest direction and splits into two main branches. During the initial exploration in January 2007, several individuals of the genus Typhlocaris, likely belonging to T. lethaea, were observed resting on the sandy muddy bottom of the first branch of a subterranean lake fed by a brackish aquifer. The animals sat in dark sections just a few meters from the platform landing stage, and the exceptional clarity of the water allowed the team to photograph and film one of them, providing the first visual evidence in decades that the species still existed.

The decisive breakthrough came in 2023, when researchers turned their attention to the Al-Coeffiah area northeast of the city. This suburban district covers roughly 835 square kilometers and is riddled with karstic features, including caves and dolines of various sizes connected by complex underground drainage systems carved into the carbonate rocks of the Benghazi Formation. In July 2023, during an exploration of the El-Khadim doline-cave, located about 15 kilometers northeast of Benghazi Port at an altitude of 21 meters, the team found a single specimen of T. lethaea resting on a rocky muddy surface just a few centimeters out of the water. It was the first new record of the species in over a hundred years, and from an entirely different cave system. During the same visit, the explorers noticed something else: a completely white isopod measuring only a few millimeters, hinting at a hidden community of depigmented subterranean life still waiting to be documented.

Three months later, in October 2023, a single specimen of T. lethaea was observed again, this time on the muddy bottom of the Al-Jebah collapse-doline cave, also within the Al-Coeffiah area. To confirm these sightings and secure physical evidence, researchers from the Departments of Zoology and Earth Sciences at the University of Benghazi returned to El-Khadim cave on December 7, 2024. Using a dip net, they collected two specimens from the surface of the first subterranean lake, preserved them in 96 percent ethanol, and transferred them to the Department of Zoology for further investigation. Both specimens proved to be female, each with a total length of five centimeters. The team also measured the physical conditions of the habitat: the average water temperature was 22 degrees Celsius, the average air temperature 21 degrees, the average pH 7.67, and the average salinity 4.72 parts per thousand, a mildly brackish chemistry consistent with the aquifer feeding these underground lakes.

Every observation of the shrimp occurred in sections of the caves characterized by complete darkness, mirroring the conditions described in Parisi’s original discovery. This consistency across sites separated by nearly a century and nine kilometers of distance carries real biological weight. The new records extend the species’ range nine kilometers north of the original Bou-Atni site into the Al-Coeffiah area, which lies just four kilometers southwest of the Mediterranean coast. Taken together with the confirmation that the shrimp persists in Lethe cave itself, the findings suggest that T. lethaea is widely distributed throughout the subterranean waters of the Benghazi plain rather than clinging to survival in a single fragile pool. The researchers note that the repeated encounters during brief visits indicate populations are likely abundant, at least in the Al-Coeffiah cave systems, and that the expanded distribution alters the species’ apparent extinction risk by adding new localities to its known range.

Perhaps the most intriguing implication concerns hydrology. The presence of the same stygobiotic shrimp in the Lethe caves of the Bou-Atni area and in the El-Khadim and Al-Jebah caves of Al-Coeffiah suggests that these underground water systems are somehow interconnected, because a species confined to groundwater cannot simply cross dry land between them. The authors argue that biospeleological methods, which analyze the DNA of subterranean stygobiotic animals to establish biogeographic connections between underground watercourses, should be used alongside traditional hydrogeological techniques to map these hidden conduits. Such an approach, they suggest, could be applied in future research not only to T. lethaea but also to other stygobiotic animals that may be prevalent in the subterranean watercourses of the region, turning the shrimp itself into a living tracer of the aquifer’s architecture.

The significance of the work extends beyond a single species. Research on cave biodiversity in Libya, and in Benghazi specifically, has never been systematically undertaken, leaving a substantial scientific gap in knowledge of subterranean organisms. The observations reported here and the earlier records from the same area represent essentially the only investigations of possible cave biodiversity in the country, and the authors describe the study as a spark intended to open new avenues of research. Future work, they argue, should fill the gaps in cave biology and ecology by potentially increasing the number of known species and addressing fundamental questions about the biodiversity and health of underground populations, including the unidentified depigmented isopod that escaped collection for lack of appropriate sampling equipment.

Conservation concerns cast a long shadow over the discovery. Typhlocaris species are classified as endangered and listed on the IUCN Red List, yet the caves in which they live are not designated as protected areas and receive no legal protection, and some have already been affected by human activity. The karst area hosting these shrimp lies outside existing protected zones and faces high levels of groundwater pumping and pollution, pressures that could rapidly degrade the very aquifers on which the species depends. The researchers emphasize that efforts must be made to engage local stakeholders in conservation actions to protect these unique cave ecosystems and the biological communities they harbor. For a species that survived a century of obscurity in the dark waters beneath Benghazi, the greatest threat now may not be anonymity but the growing human footprint above it, and the rediscovery of T. lethaea offers both a warning and a rare second chance to safeguard Libya’s hidden subterranean heritage.

Subject of Research: Rediscovery and range expansion of the blind cave shrimp Typhlocaris lethaea in subterranean karstic waters of Benghazi, Libya

Article Title: A century later: Rediscovery and range expansion of Typhlocaris lethaea Parisi, 1920 ( Crustacea , Decapoda ) in subterranean karstic waters of Benghazi, northeastern Libya

Article References: Ruggieri, R., Elbaraasi, H., Al Riaydh, M. H., Elshaafi, A., Bilal, A., Salloum, F., & Abdelmalik, M. (2025). A century later: Rediscovery and range expansion of Typhlocaris lethaea Parisi, 1920 (Crustacea, Decapoda) in subterranean karstic waters of Benghazi, northeastern Libya. Subterranean Biology, 51, 21-29. https://doi.org/10.3897/subtbiol.51.147950

Image Credits: AI Generated

DOI: 10.3897/subtbiol.51.147950

Keywords: Typhlocaris lethaea, blind cave shrimp, stygobiotic crustaceans, karst hydrology, subterranean biodiversity, Benghazi, Libya, cave conservation, Lethe cave, Al-Coeffiah caves, IUCN data-deficient, endemic species