Rare crustacean, believed to be extinct, found in a 2,500-foot-long cave

A species of lobster thought to be extinct has been found in Chilta Cave, where Dr. Matthew L. Nimmeler is diving (shown above). Credit: Amata Henkel

A cave has been discovered inside the city of Huntsville containing a small and rare crayfish that was previously thought to be extinct.

A team led by an assistant professor at the University of Alabama at Huntsville (UAH) has discovered a rare small crayfish believed to have been extinct for 30 years in a cave in the city of Huntsville in North Alabama. A lobster is a type of freshwater crustacean that resembles a small lobster.

The Shelta Cave Crayfish, known scientifically as Orconectes sheltae, was discovered by Dr. Matthew L. Nimmeler’s team during the 2019 and 2020 expeditions to Shelta Cave, its only habitat.

A study on the discoveries was published in the journal Underground biology. The study was co-authored by Dr. Niemiller, assistant professor of biological sciences at UAH University and a member of the University of Alabama System. Among the authors are Nathaniel Sturm of the University of Alabama, Catherine E. Dooley and K. Dennis Kendall Nimmler of Ohio University and Dr. Nimmeler.

The 2,500-foot-high cave system owned and operated by the National Speleological Society (NSS) is the lobster’s home. It is tucked separately under the NSS national headquarters in northwest Huntsville, and is surrounded by busy roads.

Shelta cave lobster

It is known that Shelta Cave Crayfish is only found in Shelta Cave. Credit: Dr. Matthew L. Nimmler

“Lobsters are only a few inches long with tiny pincers called dogs,” says Dr. Nimmeler. “Interestingly, crayfish have been known to cave biologists since the early 1960s, but were not formally described until 1997 by the late Dr. John Cooper and his wife Martha.”

Dr. Cooper, a biologist and speleologist who was a member of the NSS, studied aquatic life in the Chilta Cave with a particular focus on crayfish for his dissertation in the late 1960s and early 1970s. The aquatic ecosystem of the Shelta Cave was particularly diverse at the time, with at least 12 cave-based species documented, including three species of cave crayfish.

“No other cave system to date in the United States has more documented cave lobsters coinciding with each other,” says Dr. Nimmler.

But the aquatic ecosystem, including Shelta Cave Crayfish, collapsed sometime in the early 1970s. The incident may have been related to a gate that was built to keep people out of the cave yet still allow the population of gray bats to move freely in and out of the cave.

“The initial design of the gate was not suitable for bats, and eventually the bats evacuated the cave system,” says Dr. Nimmler. “In combination with groundwater contamination and possibly other stress factors, all of which may have resulted in a full-blown storm that led to the collapse of the aquatic cave ecosystem.”

Even before the decline in the aquatic cave community, the chileta cave crayfish was never very common compared to the other two species, the southern cave crayfish (Orconectes australis) and the Alabama cave crayfish (Cambarus jonesi).

“To our knowledge, only 115 individuals were confirmed from 1963 through 1975. Since then, only three have been confirmed – one in 1988 and two of the individuals we reported in 2019 and 2020,” says Dr. Nimmler.

“After two decades of no confirmed sightings and the dramatic decline documented for other watery cave life at Chilta Cave, some, including myself, feared that the lobster might now be extinct.”

While it’s encouraging that Shelta Cave Crayfish is still standing, he says scientists have not rediscovered other aquatic species that once lived in the cave system, such as the Alabama Cave Shrimp and Tennessee Cave Salamander.

“The groundwater level in Chilta Cave is the result of water naturally making its way through the layers of rock above the cave – called epikarst – from the surface,” says Dr. Nimmler. “However, urbanization in the area above the cave system may have altered the rates of water intrusion into the cave as well as increased rates of pollutants, such as pesticides and heavy metals entering the cave system.”

The crayfish was rediscovered during an aquatic survey aimed at documenting all life encountered in the cave system.

“I wasn’t really expecting to find Shelta Cave Gradfish. My students and colleagues and I visited the cave on several occasions prior to our May 2019 trip,” says Dr. Nimmeler. “We would be lucky to see only two Southern cavefish and a Southern cave lobster during the survey. “

While diving into about 15 feet of water in North Lake located in the Johns Hole section of the cave, Dr. Nimmeler spotted a smaller cave fish beneath.

“As I got around and closer, I noticed that the grapples, or pincers, were very thin and long compared to the rest of the crayfish we saw in the cave,” he says. “I was fortunate to have caught the lobster in my net and went back to the bank.”

She was a female, less than an inch long, and had internally developing eggs, so she was an adult.

“We noticed some other morphological characters, took pictures, got a tissue sample, and released the crayfish,” says Dr. Nimmeler.

“The second cave chela lobster we encountered was in August 2020 in the West Lake District,” he says.

The team searched a lot of the area and didn’t see much aquatic life. As they began to make their way out of the lake’s corridor to return to the surface, Nate Storm, the University of Alabama master’s student in biology who had accompanied the lab on the trip, noticed a small white lobster in an area the team had previously run through.

Dr. says. “I have already walked before the area and have not seen a lobster. Thank goodness for the young eyes!”

To help with identification, the team analyzed short fragments of mitochondria[{” attribute=””>DNA in the tissue samples collected.

“We compared the newly generated DNA sequences with sequences already available for other crayfish species in the region,” Dr. Niemiller says. “A challenge we faced was that no DNA sequences existed prior to our study for the Shelta Cave Crayfish, so it was a bit of a process of elimination, so to speak.”

While few crayfish are considered single-site endemics, in other words, known to exist in just one location, that’s somewhat more common in cave-dwelling species like the Shelta Cave Crayfish, he says.

“A couple other cave crayfishes are known from single cave systems in the United States. A challenge we face when trying to conserve such species is determining whether they really are known from a single cave system, or might they have slightly larger distributions but we are hampered by our ability to study life underground.”

Outside of the dissertation work done by Dr. Cooper, little about the life history and ecology of the species is known.

“The Southern Cavefish (Typhlichthys subterraneus) and Tennessee Cave Salamander (Gyrinophilus palleucus) may be predators of smaller young of the Shelta Cave Crayfish. Larger Southern Cave Crayfish and Alabama Cave Crayfish might also feed on small young,” Dr. Niemiller says.

“We know nothing of the diet of the species, but it likely is an omnivore feeding on organic matter washed or brought into the cave, as well as small invertebrates such as copepods and amphipods.”

Although this research occurred prior to the grant, Dr. Niemiller is currently conducting the first-ever comprehensive assessment of groundwater biodiversity in the central and eastern United States, a pioneering search for new species and a new understanding of the complex web of life that exists right under our feet. The research is funded by a five-year, $1.029 million National Science Foundation (NSF) CAREER award.

He says knowing the health of populations of the tiny creatures that are dependent on groundwater is important.

“Groundwater is critically important not just for the organisms that live in groundwater ecosystems, but for human society for drinking water, agriculture, etc.,” Dr. Niemiller says.

“The organisms that live in groundwater provide important benefits, such as water purification and biodegradation,” he says. “They also can act like ‘canaries in the coal mine,’ indicators of overall groundwater and ecosystem health.”

Reference: “Rediscovery and phylogenetic analysis of the Shelta Cave Crayfish (Orconectes sheltae Cooper & Cooper, 1997), a decapod (Decapoda, Cambaridae) endemic to Shelta Cave in northern Alabama, USA” by Katherine E. Dooley, K. Denise Kendall Niemiller, Nathaniel Sturm and Matthew L. Niemiller, 20 May 2022, Subterranean Biology.
DOI: 10.3897/subtbiol.43.79993

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