Rare crustaceans, believed to be extinct, found in a 2,500-meter cave

A cave in the town of Huntsville was discovered containing a small, rare crayfish previously believed to be extinct.

A team led by an assistant professor at the University of Alabama at Huntsville (UAH) has discovered a small, rare crayfish believed to have been extinct for 30 years in a cave in the northern Alabama town of Huntsville. Crayfish are a type of freshwater crustacean that resemble small lobsters.

The Shelta Cave Crayfish, scientifically known as Orconectes sheltae, was discovered by Dr. Matthew L. Niemiller during 2019 and 2020 trips to Shelta Cave, its sole habitat.

A study on the discoveries was published in the journal Underground biology. The study was co-authored by Dr. Niemiller, an assistant professor of biological sciences at UAH, a member of the University of Alabama System. Authors include Nathaniel Sturm of the University of Alabama, Katherine E. Dooley and K. Denise Kendall Niemiller of UAH, and Dr. Nimiller.

A 2,500-foot cave system owned and maintained by the National Speleological Society (NSS) is the crayfish’s home. It’s tucked discreetly under the NSS National Headquarters in northwest Huntsville and surrounded by busy roads.

“The crayfish is only a few inches long with tiny pincers called chelae,” says Dr. Nimiller. “Interestingly, the crayfish has been known to cave biologists since the early 1960s, but was 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 Shelta Cave with a particular focus on crayfish for his thesis in the late 1960s and early 1970s. Shelta Cave’s aquatic ecosystem was particularly diverse at the time, with at least 12 cave-dependent species documented, including three species of cave lobsters.

“No other cave system to date in the US has more documented cave crayfish coexisting,” said Dr. Nimiller.

But the aquatic ecosystem, including the Shelta Cave Crayfish, crashed sometime in the early 1970s. The crash may be related to a gate built to keep people out of the cave while still allowing a maternity population of gray bats to move in and out freely.

“The original gate design was not bat friendly and the bats eventually left the cave system,” says Dr. Nimiller. “Combined with groundwater pollution and perhaps other stressors, all of that could have led to a perfect storm that led to the collapse of the aquatic giant ecosystem.”

Even before the decline of the aquatic cave community, the Shelta Cave Crayfish was never common compared to the other two species, Southern Cave Crayfish (Orconectes australis) and Alabama Cave Crayfish (Cambarus jonesi).

“To our knowledge, only 115 individuals had been confirmed from 1963 to 1975. Since then, only three have been confirmed — one in 1988 and the two individuals we report in 2019 and 2020,” said Dr. Nimiller.

“After a few decades with no confirmed sightings and the documented dramatic decline of other marine life in Shelta Cave’s cave, some, myself included, feared the crayfish might now be extinct.”

While it’s encouraging that the Shelta Cave Crayfish still exists, he says scientists still haven’t 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 Shelta Cave is the result of water naturally making its way through the rock layers above the cave — called epikarst — from the surface,” says Dr Niemiller. “However, urbanization in the area above the cave system may have changed the rate at which water infiltrates the cave system and also 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 the life found in the cave system.

“I really didn’t expect to find the Shelta Cave Crayfish. My students, colleagues and I had already visited the cave several times leading up to the May 2019 trip,” says Dr. Nimiller. “We would be lucky enough to see just a few southern cave fish and southern cave lobsters during a survey.”

While snorkeling in about 15 feet of water in North Lake, located in the Jones Hall portion of the cave, Dr. Nimiller a smaller cave crayfish below him.

“As I dived and got closer, I noticed that the chelae, or pincers, were quite thin and elongated compared to other crayfish we’d seen in the cave,” he says. “I was lucky enough to drive the crayfish up with my net and returned to the bank.”

It was a female, measuring less than an inch in the length of the carapace, and had internally developing ova, so it was a mature adult.

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

“The second Shelta Cave Crayfish we encountered was in the West Lake area in August 2020,” he says.

The team had searched much of the area and didn’t see much aquatic life. As they began to leave the passageway to the lake to return to the surface, Nate Sturm, a master’s student of biology at the University of Alabama who had accompanied the lab for the trip, noticed a small white crayfish in an area the team had identified. had passed earlier.

“It was a male with thin and elongated chelae,” says Dr. Nimiller. “I had already walked in front of the area and did not see the crayfish. Thank goodness for young eyes!”

To facilitate identification, the team analyzed short fragments of mitochondrial[{” 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