Cirrate octopod from the Aglantha footage
Deep sea "garden"
The rabbitfish Harriotta haeckeli
Date:26 July 2004
Author: Ingvar Byrkjedal, Bergen Museum, Norway and Andrey Dolgov, PINRO, Russia
Cirrate octopods and tennis balls
Today's sampling station was carried out at a depth of "only" 1200 metres. A very long and successful dive with the ROV Aglantha filled a substantial part of the day. Not only were standardized transects completed without any problems, but some really spectacular scenes unfolded before the camera lens. For the first time on this cruise a cirrate, or finned, octopod was filmed in the sea. So far we have got several species of these in the trawl. But being very fragile creatures, cirrate octopods are usually retrieved from the trawl in an all but perfect condition. In fact, they are often so badly beaten that they are hardly recognizable as cephalopods.
In reality, these cephalopods are most elegant, with their umbrella-like membranes between the tentacles and with two rounded steering fins on their body. Quite suddenly one of these octopods showed up in front of Aglantha, slowly and deliberately folding its "umbrella", stretching its tentacles in a streamlined fashion, and starting to swim by movements of its two fins. There was dead silence before the screen, everybody taken by surprise by this sudden sight. In fact, the thrill factor got so high that the ROV pilot for a brief moment lost concentration and the Aglantha touched the substrate in a cloud of mud. No harm done, however, and the usual steady manoeuvering control was soon regained.
Cirrate octopods are probably quite common over the deep sea bottoms, but they may also venture higher up in the water. They have been difficult to study and little is known about their systematics, and maybe even less about thir ecology. This cruise has, however, captured a good number of individuals, and these will form an important reference collection of cirrate octopods to be housed by Bergen Museum for future study.
The Aglantha dive proceeded over a stretch of rugged and rocky bottom. Here, bright yellow bushes of Lophelia corals, red sea stars, and green cushions of Demospongiae created colourful patterns that bore a slight reminisence of a tropical coral reef. But only slightly so. Yet, spectacular they were, and we greatly enjoyed the beauty of this deepwater "garden". For the first time of this cruise black corals (Anthipatharia) were spotted as small bushes on a rocky wall.
Not all organisms are to the same extent spectacular, yet they may be just as interesting. On a stretch of muddy bottom a number of balls the size of tennis balls were discovered. They lay scattered about on the mud surface, and as many as ten of them could be spotted on the same screen frame. Aglantha enabled a close-up view of some of them, and they turned out to be a species of giant single-cell organisms, apparently belonging to one of the foraminiferan groups Xenophyophorea or Komokiea ("komoki" meaning small balls in Russian). Each of these balls consists of only one cell, and having no hard protecting cover, they are extremely difficult to sample, so therefore, needless to say, we know very little about the biology of these organisms. In fact, they are very easily overlooked. Yet, they may occur in high densities on deep sea soft sediments, as demonstrated by today's dive, and may represent a high biomass of great ecological significance.
An increase in number of seabirds (notably fulmars and great shearwaters, but also occasional manx and grey shearwaters, and kittiwakes) indicated that we have entered surface waters richer in food. And in the afternoon, just before the trawl was to be hauled, two good-sized fin whales appeared close to the ship.
The trawl catch of the day, like many of the previous catches, brought a bewildering number of rattail fishes (Macrouridae). These pose great challenges with regard to identification and, in particular, we struggle to "key out" the smaller individuals. We continue to get the outlandish rabbitfishes of genus Harriotta, the long and pliable snout of which makes one think of gigantic shrews! They are said to use the snout when probing for food in soft substrate.