At depths sunlight never penetrates and pressures would be lethal to most life, scientists have found not one but three new species of deep-sea snailfish each with its own unique shape thanks to the convergence of advanced robots, high-resolution imagery, and genetic sequencing.
The discoveries were enabled by the remotely operated vehicle Doc Ricketts of the Monterey Bay Aquarium Research Institute and the human-occupied submersible Alvin, both of which are equipped with 4K cameras, robotic arms, and precision suction samplers. In 2019, these locations ventured into abyssal depths along Central California, capturing the bumpy snailfish at 3,268 meters in Monterey Canyon and the dark and slim snailfishes at around 4,100 meters at Station M, a longstanding deep-sea research observatory. “The fact that two undescribed species of snailfishes were collected from the same place, on the same dive, at one of the better studied parts of the deep sea in the world highlights how much we still have to learn about our planet,” wrote lead author and SUNY Geneseo marine scientist Mackenzie Gerringer.
The bumpy snailfish, Careproctus colliculi, is bubblegum pink alive, with a round head, big eyes, and skin covered with minute fleshy bumps. Its wide pectoral fins have long upper rays, and a large ventral suction disk allows it to cling to the seafloor. The dark snailfish, Careproctus yanceyi, is black, with a rounded head, horizontal mouth, and smaller but well-developed suction disk. The thin snailfish, Paraliparis em, diverges from its relatives with a sinuous, laterally compressed dark body, an angled mouth, and no suction disk at all.
Determining these fishes required more than the naked eye. Researchers employed microscopy and micro-computed tomography (micro-CT) scanning to capture skeletal and soft-tissue detail at voxel resolutions as low as 15.9 micrometers. These scans enabled scientists to identify taxonomically relevant traits like vertebral counts, fin ray patterns, and tooth morphology. The team complemented this with DNA barcoding through mitochondrial cytochrome c oxidase subunit I (COI) and ribosomal 16S rRNA gene DNA sequencing. Sequence lengths ranged from 379 to 641 base pairs for COI, and GenBank and Barcode of Life database matches confirmed all three genetically distinct from known species.
The genetic work was cautious: proteinase K-digested tissue samples, DNA extracted using a Qiagen DNeasy kit, Qubit fluorometry quantitation, and amplification using quality-checked primer sets. Maximum-likelihood phylogenetic estimation placed C. colliculi in the incertae sedis clade Osteocareprocta, close to Osteodiscus cascadiae, while C. yanceyi made a low-similarity monotypic branch divergent from all deposited snailfish. P. em nested within one of the Paraliparis clades, emphasizing the paraphyletic nature of the genus.
These findings also fill a sampling gap. Liparids extend from shallow tide pools to hadal trenches greater than 8,000 meters, but abyssal depths between 3,000 and 5,000 meters have yielded relatively few specimens presumably owing to sampling bias, not absence of occurrence. The new species record that snailfishes do occur at these depths, broadening the known ecological range of the family.
The technological function was key. MBARI ROVs integrate low-light 4K imagery, adaptive LED arrays, and AI-based navigation to venture into extreme darkness and pressure, while Alvin’s human handlers have the ability to make fine-scale collection decisions in real-time. Micro-CT datasets and the gene sequences have been made available to the public via MorphoSource and GenBank and are a resource for subsequent taxonomic and evolutionary research.
For the moment, the bumpy snailfish remains known from only one confirmed sighting, though MBARI archived video hints at a putative off-Oregon sighting in 2009. The rarity of such reports helps emphasize the susceptibility and perisher of abyssal diversity. As Gerringer put it, “Our discovery of not one, but three, new species of snailfishes is a reminder of how much we have yet to learn about life on Earth and of the power of curiosity and exploration.”
