Plumed gulper

The plumed gulper is large, eel-like, and nearly impossible to observe in motion because it rarely moves. It inhabits the still lower layers of the bathyal column — the water near the Vault of Hours is notably quiescent, held between two opposing current systems — and it uses this stillness. It hangs. It waits. When prey enters the field of its detection, what happens next is fast enough that no submersible camera has caught it in a single frame.

The animal is perhaps one and a half metres in body length, excluding the dorsal plume. The plume is the arresting feature: a series of elongated modified fin-rays extending from the back of the skull to mid-body, each ending in a fleshy lobe that fluoresces faintly in the near-ultraviolet. In darkness, these lobes are visible as a scattered dim array above the body. Whether they function as lure, as camouflage, or as something else is debated.

Anatomy

The jaw is distensible and the stomach expandable, in the manner of deep-sea gulpers generally. The body musculature is dense at the head and tapers sharply toward the tail, which terminates in a narrow finned blade used for directional correction rather than sustained propulsion. The dorsal plume is not retractable. When the animal passes through particulate matter, the lobes trail micro-turbulence that is visible under beam illumination.

At the Vault of Hours

The species was first described from Vault of Hours observations, where three individuals were logged by the same pilot over a two-day survey station. Whether these were the same animals returning to the same patch of water, or different animals using the same column, is not established. The Vault's acoustic properties may be relevant; the plumed gulper appears sensitive to the low-frequency noise profiles of submersible approach and adjusts depth accordingly.