Sucker-bearing spaghetti worms from Australian seamounts get a genus of their own

The find began with a tangle that did not look like an animal. On a seamount more than 670 meters deep near the Cocos (Keeling) Islands, numerous branching brown "tentacles" stood out when a beam trawl came up ^[5]. Kupriyanova, a senior research scientist at the Australian Museum, then spotted multiple orange spheres among the branches ^[6]. "I thought that those look suspiciously a lot like polychaete eggs," she said ^[7]. Dissection showed the branching structure was the elaborate extension of a worm's tubes, and bright orange worms up to 75 mm long emerged from them ^[8].

Spaghetti worms build tubes in soft sediment and collect fine food particles from its surface with long tentacles ^[17]. The new genus name, Terebellosuctoria, means "terebellids with suckers" and was inspired by sucker-like structures on the underside of the body ^[1]. "The sucker-like structure is what makes this new genus so interesting and unique," Kupriyanova said ^[21]. The scientists named the species T. jimii after a colleague, Naoto Jimi, who had described similar sucker-like structures on another marine worm species ^[18].

Getting from a new species to a new genus took three kinds of evidence. At the museum in Sydney, Kupriyanova and an international team of taxonomists ran morphological, DNA sequencing and scanning electron microscopy analyses before concluding the worms were a previously unknown genus ^[9]. According to Hutchings, such work often combines morphological and molecular data to establish evolutionary relationships with other species ^[10].

The researchers suggested that the suckers are an adaptation among sediment-dependent groups such as spaghetti worms to living attached in sediment-scarce places such as seamount slopes ^[20].

As for how much deep-sea life is still unnamed, more than 850 worms came up on the seamount expeditions, 13 species had already been described, and this paper adds seven, so at least 20 species are now named ^[3][4][19]. The 850 are specimens, and the account gives no count of how many species they represent.

Hutchings put it in broader terms. "Only a tiny fraction has been officially named and described," she said of marine worms ^[11]. She was speaking of marine worms in general. The 850 are one collection from seamounts at two island groups ^[3]. Establishing a genus is the rarer event: finding new deep-sea species is not uncommon, but it is rare for scientists to establish a new genus ^[12].

In our view the evidence best supports a claim about pace. "An expedition may collect hundreds or thousands of specimens, but discovering what they actually are can take years," Kupriyanova said ^[13]. New species are often discovered faster than researchers can describe them ^[15]. We would hold that for this collection only. The specimens go into museum research collections, and the 2021 and 2022 voyages have so far produced at least 20 described species ^[14][19].