In this new study, Werner Schwarzhans and I investigate how bones in the inner ear of fishes, called otoliths, vary in shape and morphology across species and habitat.
We show that deep-sea fishes tend to have simpler and smaller otoliths than shallower relatives. Deep-sea conditions could constrain these bone’s ability to mineralize, causing the reductions seen here.
Future research should study how changes impact sensory landscapes in deep fishes.
Together these findings provide new insights into the drivers of otolith diversity and the evolution of fishes into deep-sea environments.
SUNY Geneseo’s Assistant Professor Mackenzie Gerringer and thirteen biology undergraduates and alums partnered with the National Oceanic and Atmospheric Administration’s (NOAA) Ocean Exploration program to study the deep seas in an online classroom. Their project, partially funded by the National Marine Sanctuaries Foundation, focused on how to use deep-sea biology data in the classroom and its educational benefits. Gerringer’s students also produced unique research findings using NOAA data that may inform conservation efforts of deep-sea ecosystems. The project results were published this week in Frontiers in Marine Science.
The article shares lessons from SUNY Geneseo’s Marine Biology course and presents a model for bringing deep-sea research into undergraduate classrooms. As Gerringer notes, access to the deep oceans is limited to a select number of researchers, in large part due to the costs of ship time. Over the years, programs like NOAA Ocean Exploration have increased accessibility to the deep seas for scientists and the public through telepresence technology. Using telepresence, the program broadcasts live footage of deep-sea exploration through a remotely operated vehicle. NOAA Ocean Exploration provides valuable opportunities for research and education by sharing the video and other data open access.
“We hope this study will inspire others to use the incredible resources that NOAA Ocean Exploration and other telepresence-enabled programs offer. Opportunities for undergraduates to engage in deep-sea research increase the accessibility and strength of the marine scientific community,” says Gerringer.
Science is a process driven by questions. In training to be scientists, students develop skills in asking these scientific questions and employing the scientific method through research. Some fields, like deep-sea biology, are challenging to bring into undergraduate classrooms. But, as the Geneseo and NOAA Ocean Exploration team show, it can be done. Students who have the opportunity to learn science content and who can practice asking questions by engaging in original research benefit academically and experience increased feelings of belonging in the sciences.
The habitat students investigated in this original research study was a deep-water coral reef off Jarvis Island, about 1,000 miles west of Hawai‘i, in the Pacific Remote Islands Marine National Monument. Coral reefs in shallow waters captivate due to their beauty, diversity, and critical ecosystem functions. Though less accessible, corals also live in deep waters, relying on plankton and sinking organic material for nutrients. Deep-sea corals extend to depths greater than 13,000 feet. These corals also contribute essential habitat to a wide diversity of other deep-sea species, including brittle stars, worms, crabs, barnacles, and fishes. Because deep-sea corals can be very slow-growing, these habitats are especially vulnerable to human impacts and are essential to study.
In the fall of 2020, the Marine Biology lab class at SUNY Geneseo studied these deep-sea coral habitats to investigate the effects of habitat rockiness, or rugosity, on the diversity and abundance of organisms in the community. Students who participated in original research during this study reported increasing their understanding of deep-sea ecosystems, gaining experience in the scientific process, and feeling stronger senses of their own science identities. The collaborative nature of the work also helped students develop their teamwork, communication, and leadership skills.
“The deep oceans are the largest habitat on our planet and are home to a beautiful diversity of organisms,” says Gerringer. “We need a broad and diverse community of researchers in the ocean sciences so that we can better understand and protect these incredible ecosystems.”
The Atacama Trench is a deep-water channel running along the Pacific coast of Chili and Peru, South America. In 2018, an international team of scientists used free-falling “landers” to study the trench, gathering images and specimens of deep-sea creatures. The team discovered a new snailfish species unique to the Atacama Trench and to all other known fish species.
The small blue fish, named Paraliparis selti by the team—“selti” meaning “blue” in Kunza, the language of the indigenous peoples of the Atacama Desert—lives in the hadal zone, waters deeper than 6000 meters, or about 20,000 feet.
Roughly 15 known species of hadal snailfishes inhabit the deep-sea trenches, with more being found each year. Most trenches house one species of snailfish, but researchers have found up to three different species occupying some trenches. These snailfishes or Liparidae, seem particularly good at living deeper than other fish. “They are not at all what we expect from a deep-sea fish,” says Linley. “I love to show people that the world’s deepest fishes are actually pretty cute.”
The team used character trait analysis, a 3D x-ray technique called microcomputed tomography (micro-CT), and genetic barcoding to show that their blue snailfish belongs to the genus Paraliparis. “Species in this genus are particularly abundant in the Southern Ocean of the Antarctic and have rarely been seen deeper than 2,000 meters.,” says Johanna Weston, postdoctoral fellow at Woods Hole Oceanographic Institution. “We were excited to see this result—this is the first time this genus has been found living in the hadal zone.”
The researchers say the new species may have evolved from the cold-adapted species of the Southern Ocean. “This little blue fish opens up new questions about the relationship between cold temperature and high-pressure adaptation and gives a new understanding of how and when life evolved into the deep,” says Mackenzie Gerringer, assistant professor at the State University of New York at Geneseo. “It’s a reminder of the unique diversity yet to be discovered thriving in the deepest parts of our oceans.”
Researchers on the team and their primary affiliations are Head of Technology Thomas D. Linley, Armatus Oceanic; Assistant professor of biology Mackenzie E. Gerringer, SUNY Geneseo; Research Fellow Heather Ritchie, Japan Agency for Marine-Earth Science and Technology; Postdoctoral Research Fellow Johanna N. J. Weston, Newcastle University; 3D Visualization Specialist Amy Scott-Murray, The Natural History Museum, London; CT Facility Manager Vincent Fernandez, The Natural History Museum, London; Jhoann L. Canto, Chief of Vertebrate Zoology, Museo Nacional de Historia Natural, Santiago, Chile; Professor Frank Wenzhöfer, University of Southern Denmark; Professor Ronnie N. Glud, University of Southern Denmark; Professor Alan J. Jamieson, University of Western Australia.
Funding & Acknowledgements
HADES-ERC Advanced grant “Benthic diagenesis and microbiology of hadal trenches” grant (agreement number 669947) awarded to Ronnie N Glud (University of Southern Denmark)
RV Sonne cruise SO261 (ship time provided by BMBF, Germany)
Osvaldo Ulloa of the Instituto Milenio de Oceanografía, Universidad de Concepción (IMO-UdeC, Chile) for, on behalf of Chile, loaning us the specimen from their waters so that we may describe it.
We have been grateful to be selected as one of seven recipients of an Ocean Exploration Education Mini-Grant from NOAA Ocean Exploration and the National Marine Sanctuary Foundation in 2022. Our multi-part project was designed to support students from backgrounds historically underserved and/or underrepresented in ocean exploration with research and professional development opportunities. To share resources and strategies for students from diverse backgrounds interested in entering the marine science and/or STEAM workforce, Gerringer developed a semester-long professional development and discussion series for which the entire Biology Department was invited. Additionally, project funds supported the recruitment and training of three undergraduate students from historically excluded backgrounds in marine research and analysis techniques. This student team and others in the lab worked together on an independent research project on deep-sea fish abundance and diversity using NOAA Ocean Exploration video footage collected by ROV Deep Discoverer and presented their findings at GREAT Day, SUNY Geneseo’s student research symposium.
Learn more about this research from the NOAA article, blog from Nikki Fuller (SUNY Geneseo ’22), and science communication poem from Gabriel Rosado (SUNY Geneseo ’22), linked below!
One of our research team’s main goals is to understand how fishes have evolved and adapted into deep-sea environments. In our new paper in Marine Biology, we explore what it takes for fishes to live at the ocean’s greatest depths.
Bony fishes are extremely successful in the marine environment, having evolved into nearly every ocean habitat. However, bony fishes do not seem to inhabit the ocean’s deepest depths, likely due to constraints of pressure adaptation. How deep do bony fishes live?
Few studies have examined the deepest living vertebrates, because sampling in hadal environments, depths 6000–11,000 m, is technologically challenging. In this study, we review the literature on records of the deepest living bony fishes.
Current depth records are held by the hadal snailfish Pseudoliparis swirei (family Liparidae) in the Mariana Trench, collection depth 7966 m, filmed to 8178 m, and the cusk eel Abyssobrotula galatheae (family Ophidiidae) in the Puerto Rico Trench, collection depth 7965 m.
Observations of abyssal and hadal fish communities suggest that hadal snailfishes are endemic to trenches but occasionally cross into abyssal areas. On the other hand, cusk eels dwell on the abyssal plains, but can extend their ranges into the trenches. These habitat differences allow both snailfishes and cusk eels to occupy distinct niches in the greatest ocean depths.
We then comment on the ecological and physiological significance of these two major hadal families and present recommendations for future research.
This paper has been featured as a Highlight Article, with editorial comment from Dr. Scott Hamilton available here.
We tested the hypothesis that deep-sea fishes have poorly mineralized bone relative to shallower-dwelling species using data from a single family that spans a large depth range. The family Liparidae (snailfishes, Cottiformes) has representatives across the entire habitable depth range for bony fishes (0 m–> 8000 m), making them an ideal model for studying depth-related trends in a confined phylogeny.
We used micro-computed tomography (micro-CT) scanning to test three aspects of skeletal reduction in snailfishes (50 species) across a full range of habitat depths: 1) reduction of structural dimensions, 2) loss of skeletal elements, and 3) reduction in bone density.
Using depth data from the literature, we found that with increasing depth, the length of the dentary, neurocranium, and suborbital bones decreases. The ventral suction disk decreases width with increasing maximum habitat depth and is lost entirely in some deeper-living taxa, though not all.
Although visual declines in bone density in deeper-living taxa were evident across full skeletons, individual densities of the lower jaw, vertebra, suction disk, hypural plate, and otoliths did not significantly decline with any depth metric.
However, pelagic and polar taxa tended to show lower density bones compared to other species in the family.
We propose that skeletal reductions allow snailfishes to maintain neutral buoyancy at great depths in the water column, while supporting efficient feeding and locomotion strategies. These findings suggest that changes in skeletal structure are non-linear and are driven not only by hydrostatic pressure, but by other environmental factors and by evolutionary ancestry, calling the existing paradigm into question.
The remotely-operated vehicle, Deep Discoverer, explores the deep sea live, while anyone with an internet connection can tune in. The sense of excitement and discovery is palpable. As we watch NOAA’s Okeanos Explorer live feed, we sometimes discuss: what would be the top things you would want to see. This fish made the top of our lists and last year, we saw it! It’s an aphyonine cusk eel, in the family Ophidiidae, and this is the first time one has been seen alive!
Some deep-sea fish are full of a gelatinous goo—a watery tissue layer. These tissues show up in several different types of fishes, but why are they there? Our new open-access paper in Royal Society Open Science tackles this question. We describe which fishes have gelatinous tissue, show the chemistry of what gelatinous tissues are made of, and test some of the functions. Gelatinous tissues likely help deep-sea fishes maintain buoyancy. They may also act as faring, changing the shape of the fish to reduce drag. And, of course, we needed to build a robot hadal snailfish! Check out the full paper and coverage by Science News!