The tripod fish, Bathypterois viridensis, with parasitic isopods attached to two of its fins. Tripod fishes rest on the seafloor on the tips of elongated rays of their pelvic and lower caudal fins. They use the elongated rays of their pectoral fins as sensory “antennae” that project out and forward as the fish sits facing into the current. Image courtesy of the NOAA Office of Ocean Exploration and Research, Gulf of Mexico 2017. Download larger version (jpg, 732 KB).
A coronate medusa, Periphylla periphylla, that collided with the seafloor. These medusae undertake a daily vertical migration (toward the surface at dusk and toward the depths at dawn). It is suspected that this was a reaction to the bright lights on Deep Discoverer; the medusae attempted to swim deeper away from the light they thought was coming from the surface. Image courtesy of the NOAA Office of Ocean Exploration and Research, Gulf of Mexico 2017. Download larger version (jpg, 1.0 MB).
An olive-colored empty egg case of a cartilaginous fish – either a skate, ray, or shark – attached to the octocoral Swiftia koreni. Image courtesy of the NOAA Office of Ocean Exploration and Research, Gulf of Mexico 2017. Download larger version (jpg, 998 KB).

Dive 14: “Penchant Basin”

December 17, 2017

Dive 14: Cartoon Chimaera

A chimaera seen during Dive 14 of the expedition. These fish are also known as rabbit fishes and spook fishes. Video courtesy of the NOAA Office of Ocean Exploration and Research, Gulf of Mexico 2017. Download larger version (mp4, 21.1 MB).

Today’s dive took place at “Penchant Basin,” a geologically active site where possible seeps had been detected via seismic and multibeam surveys. Deep Discoverer touched down at a depth of 800 meters (2,625 feet) on a sedimented seafloor with an abundance of benthopelagic fauna, including many fish species and gelatinous creatures, such as ctenophores, jellies, and siphonophores. Moving upslope, the seafloor was covered with many burrows and mounds, which provided habitat for crustaceans, including blind lobsters (Acanthacaris caeca), giant isopods (Bathynomus giganteus), and galatheid squat lobsters. We also observed small areas of reduced sediments in shallow depressions with bacterial mats, empty vesicomyid (clam) shells, gastropods, tubeworms, and cusk eels. Towards the summit of the slope, we saw two straight-edged elongated carbonate ridges colonized by several coral species, as well as brachiopods, zoanthids, spiny crabs, and encrusting demosponges. One of the most interesting observations for the dive was several elasmobranch (cartilaginous fish) egg cases attached to the octocorals and antipatharians, indicating that these corals are a nursery for elasmobranchsa. Curiously, many of the egg cases had been overgrown by coral tissue with polyps.