Set up for a long life

In the depths of the ocean, life can extend far beyond its usual limits. Take the tube worm Escarpia laminata: living in an environment with a year-round abundance of food and no predators, individuals seem to live for over 300 years. And some may be 1000 years old or more – meaning they would have been around when William the Conqueror invaded England.

“E. laminata is pushing the bounds of what we thought was possible for longevity,” says Alanna Durkin at Temple University in Philadelphia, Pennsylvania.

These tube worms live between 1000 and 3300 metres below sea level in aggregations from five to more than 200 individuals around cold seeps. This environment also provides a habitat for brittlestars, shrimps, crabs, mussels, clams, snails, limpets and a huge variety of smaller species of worms.

“The tube worms look like oversized plastic straws with a delicate pink flower at the end when the animal extends its petal-like plume – a gill-like organ for gas exchange – out of the top of its tube,” says Durkin. They can measure more than 1.5 metres, and feed through a symbiotic relationship they form with bacteria that thrive in these seeps.

Growth model

Finding out exactly how old the worms were was tricky, says Durkin, given that they don’t produce a hard, permanent skeleton or tissue with annual, countable “growth rings”. Instead, her team had to rely on a growth model from an earlier study of a different worm species, which predicts how much a worm grows each year.

“The idea behind the growth model is that it lets us simulate how these tube worms grow and age without us having to wait hundreds of years to watch them grow in real time,” says Durkin.

Researchers fed real-life data into the model by looking at how much worms of different sizes grew over a single year. This served to reveal how fast they grow at varying stages of their lives, Durkin explains.

“Then we can use that data to simulate tube worms growing over time to find out how many years it would take these animals to reach a particular size,” she says.

According to the model, some of the tube worms have been around for hundreds of years – with some maybe even thousands of years old. It is hard to put an upper limit on their age, because they grow more slowly as they get older.

“There may indeed be large E. laminata over 1000 years old in nature, but given our research we are more confident reporting a lifespan of at least 250 to 300 years,” says Durkin.

Long-lived species of the deep

This suggests that the tube worms are the second-longest-living non-colonial species ever found in the depths of the ocean – the deep-sea clam Arctica islandica can live for 500 years or more. Colony-forming animals, including some corals, are estimated to live for over 4000 years.

“It’s possible that new record-breaking lifespans will be discovered in the deep sea, since we are finding new species and new habitats almost every time we send down a submersible,” says Durkin.

Journal reference: The Science of Nature, DOI: 10.1007/s00114-017-1479-z