New Antarctic Starfish Are Doting Parents and Vicious Predators

by Pelican Press
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Christopher Mah, a biologist at the Smithsonian, was scouring the shelves of the museum for deep-sea starfish when he had an idea: Why not see if any of the specimens were preserved with their last meal still digesting inside of them, to help understand their natural diet?

Following this whim, he cut open a preserved stellar sea creature from Antarctica, but instead of food, he found new life frozen in time within the creature’s coelomic cavity. There were around 10 baby sea stars, each the spitting image of their parent, which like many starfish was probably hermaphroditic.

Dr. Mah described the brooding starfish as a new species, Paralophaster ferax. He published the finding, along with a plethora of other natural history observations of Antarctic starfish, in the journal Zootaxa in June.

Dr. Mah also describes a new genus of starfish and 10 additional new species. Starfish are invertebrates of the class Asteroidea, so they’re also known as asteroids (yes, another cosmic name). You have to go back to 1940 to find “the last time a novel brooding species from Antarctica was described,” Dr. Mah said.

P. ferax is unlike most starfish species, which reproduce by shooting their eggs and sperm into the water and leave their young to fend for themselves. But the habit of holding onto offspring — brooding — has evolved multiple times and is especially common in Antarctic waters.

The popularity of parental care in Antarctic asteroids may have to do with the strength of the currents flowing through their frigid homes, said Cintia Fraysse, a starfish biologist at the Austral Center for Scientific Research in Ushuaia, Argentina. “The currents are tough, so it’s hard to reach the seafloor to settle as a larva,” Dr. Fraysse said.

Many species are also so deep down that sunlight can’t reach photosynthetic plankton, leaving the larvae with little food to eat. For the babies to survive, it makes sense for a parent to raise them until they’re big enough to scuttle off on their own.

While many starfish brood their young, they don’t all use the same parenting strategies. Some, like P. ferax, hold their little starlets in a special body cavity; others just put them in their mouths. Still others have developed baby-carrier-esque structures between their arms to hold the juveniles. “Kind of like an armpit cage,” Dr. Mah said.

While finding brooding babies was a pleasant surprise for Dr. Mah, his instinct to check out whether the starfish were caught chewing their food also proved fruitful for his original question. One specimen, an Antarctic sun star or Solaster regularis, had a smaller, partially digested starfish of the species Anasterias antarcticus in its mouth.

Often erroneously seen as docile or motionless, starfish are in fact voracious predators, Dr. Fraysse said, preying on sea urchins, crabs and, as Dr. Mah saw, even other starfish. “They control the benthic ecosystem,” Dr. Fraysse said. “They extend the stomach out of the mouth” so they can eat things bigger than themselves. One particularly ravenous specimen, kept at the Smithsonian but not used for this study, has the arm of another starfish sticking out of its mouth.

Dr. Mah didn’t have to travel to Antarctica to make these discoveries — he just had to go to work. Most of the deep-sea star specimens were collected in the 1960s by the U.S. Antarctic Research Program. When they ended up at the Smithsonian in 2010 nobody paid much attention to them. Dr. Mah hopes his work will shine a spotlight on the importance of good old-fashioned organismal biology.

“Very few people get down to species level and investigate the critters the way that people used to,” he said.

Observing the natural history of animals, be they in nature or sitting on a museum shelf, provides the foundation that the rest of zoology depends on. “When we do physiology or reproduction,” Dr. Fraysse said, “this kind of work makes it easier for us.”

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