An international team of researchers identified a new genus of deep-sea marine worms, with suction-cup-like structures on the underside of their bodies. The discovery strengthens knowledge of the still-unknown biodiversity of the seabed around Australia.
The new genus, named Terebellosuctoria, belongs to the polychaetes, a class of marine worms with a segmented body and lateral appendages equipped with numerous bristles. Although they may resemble centipedes, these animals are close relatives of terrestrial earthworms.
The designation Terebellosuctoria, which means “terebellids with suction cups,” was inspired by the unusual structures found on the underside of the body. According to Elena Kupriyanova, senior researcher at the Australian Museum, the uniqueness of these structures drew scientists’ attention when the specimens were presented to the other authors of the study.
Identification of new species in deep-water environments is not unusual, but the discovery of a genus previously unknown is rarer, since this rank of biological classification is above species.
Worms hidden in branched structures
The study, published in July in the scientific journal Records of the Australian Museum, analyzed specimens collected during expeditions conducted in 2021 and 2022 aboard the CSIRO research vessel Investigator. The campaigns, led by Museums Victoria, explored seamounts off Christmas Island and the Cocos (Keeling) Islands.
During these expeditions more than 850 marine worms were collected. Thirteen new species for science had already been described, and the new work adds seven more, belonging to three families. Two of these species belong to the genus Terebellosuctoria, of the family Terebellidae.
One of the specimens was found on a seamount more than 670 meters deep, near the Cocos (Keeling) Islands. When the researchers brought the organisms to the surface, they observed branching brown structures, among which small orange spheres stood out.
Kupriyanova suspected these spheres might be polychaete eggs. A more detailed analysis, including dissection, revealed that the branched structure was not an independent animal, but rather an elaborate extension of the tubes built by the worms.
The so-called “spaghetti worms” live in tubes installed in soft sediments and have numerous long tentacles, which they use to collect food particles from the sediment surface. From the analysed tubes emerged vividly orange marine worms, some up to 75 millimeters in length.
One of the new species was named Terebellosuctoria jimii, in honor of Naoto Jimi, a researcher who had described suction-cup-like structures in another species of marine worm.
Back at the Australian Museum in Sydney, Kupriyanova and an international team of taxonomists turned to morphological analysis, DNA sequencing, and scanning electron microscopy. The results allowed concluding that the specimens did not represent merely a new species but a genus hitherto unknown.
The researchers suggest that the suction-cup-like structures may constitute an adaptation to life in environments with little available sediment, such as the slopes of seamounts, enabling these animals to remain attached.
Naming species is also documenting biodiversity
Marine worms are among the most diverse and abundant animals on the ocean floors. Some can reach three meters in length, and many play important roles in nutrient recycling.
Despite their ecological relevance, they remain little known. Only a small portion of marine invertebrates has been formally identified and described, and the classification process can take years.
An expedition can collect hundreds or thousands of specimens, but determining which species they belong to requires detailed analyses and, often, different investigative methods. The specimens are preserved in scientific museum collections, where they can continue to be studied long after the expedition has ended.
Pat Hutchings, a marine worm specialist and senior research associate at the Australian Museum, notes that taxonomy is not limited to naming organisms. The process involves documenting and analyzing their characteristics, using, for example, morphological and molecular data to establish evolutionary relationships with other species.
The description of these seven new species represents another step in identifying the biodiversity that remains to be known in the oceans.
