Yesterday the DSN crew first saw the video above. What is this large floating sheet of goo? Is it alive? Was it once alive?
The two leading contenders seems to be that it is A) an old whale placenta or B) a rare and enigmatic deep-sea jellyfish. And the answer is…. B)
A) So why is not an old whale placenta? The video is from approximately 5000 feet (1500 m). A placenta would need to sink to this depth without any other organism consuming it. Unlikely given that its rate of decent would have been slow and any organic food source in the deep sea is unlikely to last long.
B) So why is it a jellyfish?* In 1967, F.S. Russell described a very enigmatic deep-sea jellyfish, Deepstaria enigmatica.
During Dive 159 of the U.S. research submersible Deepstar 400 on 22 October 1966 Dr. Eric G. Barham, Dr. George Pickwell, and Mr. Ronald Church collected a remarkable scyphomedusan at a depth of about 723 m in the San Diego Trough…when first noted, the jellyfish’s margin was collapsed and the [outer, convex surface of the umbrella] indented.
In other words it didn’t look like much of a jellyfish. Sound familiar?
On opposite sides of the umbrella are two large tubular shaped processes…It has a yellowish brown tinge…The radial canal system is most striking. It consists of a meshwork, likened by Dr. Barham to wire-netting.
The meshwork, wire-netting like, radial canal system of Deepstaria enigmatica
The gonads are situated along the margins of fan-shape mesenteries, and tend to be broken up into several isolated processes with incurved edges.
Gonads on a fan shaped protrusion
Figure from Russell 1967
Specimen of Deepstaria enigmatica described by Russell 1967
In 1988 Larson and colleagues published further work describing this rare group of jellyfish. They too noted the unique canal system. But it is these researcher’s behavioral notes that I find most interesting.
These two species of Deepstaria display some unique behaviour; peristaltic locomotion and pursing of the bell margin are unknown in other medusae. Probably the peristaltic locomotion is necessary because the umbrella is too thin and the subumbrella musculature too diffuse to support more rapid pulsation. Our observations of both species of Deepstaria suggest that they usually hang motionless with the umbrella open…It seems probable to us that medusae in this genus are large ambush predators in the meso- and bathypelagic environment…we speculate that the feeding behaviour might be as follows. The medusae usually hang vertically and motionless with the bell open; occasional peristaltic contractions probably enable them to swim slowly, at least enough to retard sinking. Because the area of the subumbrella is so large, upward-swimming prey occasionally would swim into it. Once prey enter the large subumbrellar chamber, the contact stimulates rapid contraction of the coronal muscle, pursing the umbrella shut and trapping the prey. As the prey attempts to escape, it contacts nematocysts on the subumbrella, being repeatedly stung until weakened. It may additionally become covered with mucus and further immobilized. Then peristalsis and ciliary movement could transport the prey towards the mouth where the oral arms could grasp and engulf it…’Bagging’ prey in this way is not known in other medusae.
Plate 4 One of the large gelatinous organisms, Deepstaria enigmatica, that have been recently found to be very abundant in mesopelagic waters of the world ocean. This medusa was photographed in Monterey Bay by Kevin Raskoff © MBARI, 1998.
Russell, F. S. (1967). “On a remarkable new scyphomedusan Deepstaria enigmatica”. Journal of the Marine Biological Association of the UK 47: 469-473.
Larson, R.; Madin L., Harbison, G. (1988). “In situ observations of deep water medusae of the genus Deepstaria, with a description of D. reticulum sp. nov.”. Journal of the Marine Biological Association of the UK 68: 689-699.
*UPDATE: This has now also been confirmed by Dr. Steven Haddock of the Monterey Bay Aquarium Research Center, an expert on deep-sea and pelagic creatures.
UPDATE2: Steven Haddock provides some much better photos of Deepstaria engimatica on the Jellyfish Watch Facebook page.
UPDATE3: Several comments below suggest the species is Deepstaria reticulum. Important thing is that it is still a jellyfish and already known.