Rare crustacean, thought to be extinct, found in 2,500ft long cave

A species of crayfish thought to be extinct has been discovered in Shelta Cave, where Dr. Matthew L. Niemiller is snorkeling (see above). 1 credit

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

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

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

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

A 2,500 foot cave system owned and maintained by the National Speleological Society (NSS) is the home of the crayfish. It’s tucked away discreetly below the NSS national headquarters northwest of Huntsville, and it’s surrounded by busy roads.

Shelta Cave Crayfish

The Shelta Cave Crayfish is known to only exist in Shelta Cave. Credit: Dr. Matthew L. Niemiller

“The crayfish is only a few inches long with tiny claws called chelae,” says Dr. Niemiller. “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.”

NSS biologist and caver Dr Cooper studied aquatic life in Shelta Cave with particular emphasis on crayfish for his thesis work in the late 1960s and early 1970s. Shelta Cave was then particularly diverse, with at least 12 cave-dependent species documented, including three species of cave crayfish.

“No other cave system to date in the United States has more documented cave crayfish coexistence,” says Dr. Niemiller.

But the aquatic ecosystem, including the Shelta Cave crayfish, crashed in the early 1970s. The accident may be linked to a door that was built to prevent people from entering the cave while allowing a population of gray bat maternities to enter and exit freely.

“The initial gate design was not bat-friendly, and the bats eventually left the cave system,” says Dr Niemiller. “Coupled with groundwater pollution and possibly other stressors, all of this may have led to a perfect storm causing the aquatic cave ecosystem to collapse.”

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

“To the best of 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,” says Dr Niemiller.

“After a few decades of no confirmed sightings and the documented dramatic decline of other aquatic cave species at Shelta Cave, some, including myself, feared that the crayfish were now extinct.”

While it’s encouraging that the Shelta Cave Crayfish persists, he says scientists still haven’t rediscovered other aquatic species that once lived in the cave system, such as the Shelta Cave Shrimp. Alabama and the Tennessee cave salamander.

“The groundwater level in Shelta Cave is the result of water naturally forcing 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 altered the rates of water infiltration into the cave and also increased the levels of pollutants, such as pesticides and heavy metals entering the cave. cave system.”

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

“I really didn’t expect to find the Shelta Cave crayfish. My students, my colleagues and I had already visited the cave several times before the May 2019 trip,” explains Dr Niemiller. “We would be lucky to only see a few southern cavefish and southern cave crayfish when surveyed.”

While diving in about 15 feet of water in North Lake located in the Jones Hall section of the cave, Dr. Niemiller spotted a smaller cave crayfish below him.

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

It was a female, measuring less than an inch in carapace length, and had developing eggs inside, so it was a mature adult.

“We noted other morphological characters, took photographs, acquired a tissue sample and released the crayfish,” says Dr. Niemiller.

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

The team had searched much of the area and had not seen much aquatic life. As they began to climb out of the lake passage to return to the surface, Nate Sturm, a master’s student in biology at the University of Alabama who had accompanied the lab on the trip, noticed a small white crayfish in an area the team had traveled before.

“It was a male with thin, elongated claws,” says Dr. Niemiller. “I had walked past the area before and didn’t see the crayfish. Thank goodness for the young eyes!

To aid 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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