El Nino rains could aid research on the population of California giant salamanders—or their close, not fully formed relatives—found in the Porter Cave system under UC-Santa Cruz.
by Madeleine Turner
Jan. 21, 2016—Porter Cave is known for being popular with college freshmen. Party-goers deposit their beer bottles and empty paint cans on the cave’s floor. Walls drip with graffiti. But below this debris lies a mysterious world—Porter Cave (also known as Empire Cave) is one entrance to a vast network of caverns.
UC Santa Cruz sits on two crisscrossing fault lines. The overlapping lines create schisms where water flows through and creates more space. The caves run in multiple directions under campus. The same processes have been in motion for an unfathomable time; the network of caves under UC Santa Cruz are millions of years old.
We’re too big to squeeze into the crevices beyond Empire Cave, but innumerable creatures can and do. Some of these species are so weird that they don’t have common names. Scientists may refer to them— but only by their latin genus. There are others, however, who do have common names. One is Dicamptodon ensatus, known as the California Giant Salamander.
Adults are kings and queens of the salamander world. Including tails, they can grow up to a foot in length. Some have black and tan jigsaw puzzles printed on their backs- like little amphibian jaguars. They have pale bellies and thick tails shaped like paddles, blades on either side.
Salamanders are amphibians; they need and like the wet. Adults pad along streamside and look for banana slugs to slurp. But before adulthood, Giant Salamanders actually have a larval stage.
Larvae look similar to adults, but with bigger tails and skimpy legs. They must live in water to survive. Gills are stuffed out the sides of their necks. Larvae seem capable of whipping their paddle tails back and forth to squirm away in a pinch. But instead they sit still, their torsos poised above the riverbed and their toes barely scraping the bottom. They look Zen.
Salamanders undergo metamorphosis, just like tadpoles transforming into frogs. A decade ago, however, Barry Sinervo noticed something weird: salamander larvae in Empire Cave never seemed to turn into full blown adults.
In any giant salamander population, a few larvae may never metamorphose. These oddballs live in local streams. They never leave the water, but they grow bigger and reproduce like normal adults. This phenomena is known as paedomorphosis.
Sinervo, an Ecology and Evolutionary Biology professor at UC Santa Cruz, says, “If salamanders happen to come [into the caves] and they’re paedomorphic, they might survive. But they may in fact be breeding in there.”
Paedomorphic salamanders are the minority aboveground, but people have discovered them in high numbers within other cave systems.
California Giant Salamander Larvae look similar to terrestrial adults, sans splotches. Spy them in local streams. ( Photo by Gary Nafis)
Uniquely Santa Cruz Salamanders?
A decade ago, Sinervo and his UCSC herpetology class began collecting larvae from Empire Cave and adjacent streams so they could compare the above and belowground populations. Maybe the stream and cave populations are genetically identical, despite their different life histories, and cave salamanders weren’t metamorphosing because they lived confined in the cave.
But maybe they are two different species. Maybe the cave population evolved and lost the ability to metamorphose.
Could a unique salamander species be thriving under the UC Santa Cruz Campus?
To find out, they raised both groups of larvae in a lab. If stream and cave populations were the same species, both groups should’ve transformed into adults in a controlled environment.
But as larvae from the stream grew their jaguar spots and shrunk their paddle tails, cave larvae stuck to the water and never turned into terrestrial adults. This is evidence that the Empire Cave population may be a separate species.
“I don’t know if this is a unique species,” Sinervo says. Genetic tests would be needed to confirm anything.
There are other unique species in this particular cave system, including two unnamed crustaceans- an aquatic isopod and amphipod. They are proven to be endemic, meaning they live nowhere else on earth. It’s also likely that they’re the underground salamander’s food of choice.
If other creatures had time to take up this underground real-estate and evolve into new species, maybe salamanders had time to do the same.
Since Empire Cave is only a porthole to the greater cave system, it’s impossible to say how many underground salamanders there could be. “We happen to have one or two salamanders with territory that comes up the little holes that go into the Empire Cave,” Sinervo says, “There may be a stable population, but we only see the tip of the iceberg.”
Sinervo’s study happened before the drought. In recent years water levels haven’t risen high enough to permeate Empire Cave, making it impossible to collect salamander larvae and continue further work. Water levels might rise high enough this year, after more rain.
Empire Cave and its adjoining networks are in the dark, figuratively. People could do more work to understand the underground Giant Salamander population, or any of the other cave species.
Aboveground activities could have an effect on underground ecosystems.
“We have to be very careful about certain things," Sinervo says, "People drive up to campus and park their cars. Oil drips off their cars, and water carries oil into the cave gulch ecosystem. It’s not a great situation.”
Sinervo would like to see regulations to protect the salamanders and the cave they inhabit. If these salamanders are in fact a separate species, they could become subject to protection under the Endangered Species Act. But if they aren’t unique, there could be other ways to indirectly protect them and their cave ecosystem.
Sinervo points out that there are other very rare species living in the cave, such as the blind cave amphipod and isopod, that could be protected under law; doing so would indirectly protect the paedomorphic giant salamanders. "They're just not on the endangered species [list]," he says.
But, “Life is life. The Endangered Species Act isn’t the Endangered Vertebrate Act,” Sinervo says, “It’s pretty clear, it should be equal protection under the law.”