In situ Observations of the Meso-Bathypelagic Scyphozoan,Deepstaria enigmatica(Semaeostomeae: Ulmaridae)

Abstract

Deepstaria enigmatica (Semaeostomeae: Ulmaridae) is one of the largest and most mysterious invertebrate predators of the deep sea. Humans have encountered this jellyfish on only a few occasions and many questions related to its biology, distribution, diet, environmental tolerances, and behavior remain unanswered. In the 45 years since its formal description, there have been few recorded observations of D. enigmatica, due to the challenging nature of encountering these delicate soft-bodied organisms. Members of Deepstaria, which comprises two described species, D. enigmatica and D. reticulum, reside in the meso-bathypelagic region of the world's oceans, at depths ranging from ∼600 to 1750 m. Here we report observations of a large D. enigmatica (68.3 cm length × 55.7 cm diameter) using a custom color high-definition low-light imaging system mounted on a scientific remotely operated vehicle (ROV). Observations were made of a specimen capturing or “bagging” prey, and we report on the kinetics of the closing motion of its membranelike umbrella. In the same area, we also noted a Deepstaria “jelly-fall” carcass with a high density of crustaceans feeding on its tissue and surrounding the carcass. These observations provide direct evidence of singular Deepstaria carcasses acting as jelly falls, which only recently have been reported to be a significant food source in the deep sea.