Meeting Abstract
Some deep-dwelling fishes have a gelatinous layer either directly below the skin or around the spine in the caudal region. We investigated the composition and potential function of this gelatinous tissue. Gel samples from eight deep-water species were analyzed for water content (97.14 ± 1.19%), ionic composition, and osmolality, bulk protein (0.4 ± 0.2 %), lipid (0.93 ± 0.01 %), and carbohydrate (0.6 ± 0.28%). These suggest that the gel is mostly extracellular fluid. These analyses do not support the hypotheses that this tissue plays a role in nutrient storage in an energy-limited environment or buoyancy in a high-pressure one. The gelatinous layer is most prominent in the hadal snailfish Notoliparis kermadecensis, one of the planet’s deepest-living fishes, making it an interesting model organism to investigate gel function. The authors propose that the gelatinous tissue may act as an energetically inexpensive method of increasing swimming efficiency by fairing the transition from trunk to tail. Swimming performance in the gelatinous hadal snailfish was compared to swimming performance in the tidal snailfish, Liparis florae, which have similar morphology, but no subcutaneous gel. Video analyses show that Liparis florae swam more body lengths per second than their hadal counterparts. A robotic snailfish model was also used to analyze the impacts of the gelatinous layer on locomotory performance. The model swam faster with a water layer, representing gel, around the silicone tail than with the silicone tail alone. Data from these three analyses suggest that the gelatinous layer may aid hadal snailfish locomotion at a low energetic cost.
