An international team of marine biologists has described two new species of the polychaete worm genus Melinnopsis from deep waters off the east coast of Australia.
Light microscope images of Melinnopsis gardelli: (A) holotype, lateral view of complete specimen; (B) holotype, dorsal view of anterior region, arrow indicates postbranchial dorsal membrane; (C) holotype prostomium, arrow indicates slightly raised lip; (D) lateral view of anterior region, arrows indicate acicular neurochaetae and (E) ventral view of anterior region showing ventral shields. Scale bars – 1 mm. Image credit: Gunton et al, doi: 10.3853/j.2201-4349.72.2020.1763.
Polychaete worms are closely related to leeches and earthworms and together make up the phylum Annelida.
These segmented worms are among the most common marine organisms, and can be found living in the depths of the ocean, floating free near the surface, or burrowing in the mud and sand of the beach. Some, such as Eunice gigantea, may reach 3 m (10 feet) long.
The newfound polychaete species, named Melinnopsis gardelli and Melinnopsis chadwicki, inhabit the deep waters from Coral Sea Marine Park to Hunter Marine Park off the east coast of Australia.
They live in the sediment on the seafloor and use long tentacles, which they spread across the sediment surface to collect tiny food particles.
“The discovery of these species of deep-sea worm helps us to better understand the biodiversity of the ocean floor,” said lead author Dr. Laetitia Gunton, a researcher in the Australian Museum Research Institute.
“They may be small, around 4 cm (1.6 inches) long, but these worms play a very important role in the deep-sea ecosystem.”
“Deep-sea sediments are teeming with worms eating up bits of food and recycling those nutrients back into the deep-sea food web.”
Light microscope images of Melinnopsis chadwicki: (A) holotype, lateral view of entire specimen, (a) pygidium; (B) holotype, lateral view of anterior part; (C) prostomium, arrows indicate transverse nuchal organs; (D) holotype, sediment tube. Scale bars – 1 mm in (A and B), 0.5 mm in (C) and 2 mm in (D). Image credit: Gunton et al, doi: 10.3853/j.2201-4349.72.2020.1763.
The two new species were collected during RV Investigator’s ‘Sampling the Abyss’ voyage in May-June 2017 using a beam trawl.
Melinnopsis gardelli was collected around 2,500 m (8,202 feet) and Melinnopsis chadwicki around 1,000 m (3,281 feet) depth.
“These species form a monophyletic clade and are genetically distinct from each other and all other analyzed polychaete species,” the scientists said.
The discovery is reported in a paper in the Records of the Australian Museum.
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Laetitia M. Gunton et al. 2020. Two New Deep-water Species of Ampharetidae (Annelida: Polychaeta) from the Eastern Australian Continental Margin. Records of the Australian Museum 72 (4): 101-121; doi: 10.3853/j.2201-4349.72.2020.1763
