Lophodolos acanthognathus, a deep-sea anglerfish
Teuthowenia megalops, juvenile
Teuthowenia megalops, adult
Date:June 10, 2004
Author: Annelies Pierrot-Bults, Univ. Amsterdam; Tracey Sutton, Harbor Branch Oceanographic Institution; Dick Young, Univ. of Hawaii
Most of the day was taken up by processing the samples, which were made yesterday, last night, and morning today. The whole group of scientists was busy all night, regardless of their watch, because nobody wanted to miss the opportunity to see what was there and to help with processing the samples. So we did not get much sleep today. In all, thousands of fish specimens were preserved or frozen for later analyses. Catches were dominated by lanternfishes, deep-sea smelts, and dragonfishes, but rarer fishes were also caught including deep-sea anglerfishes and daggertooths.
Cephalopods were not abundant in the catch but some interesting species were caught. The most interesting was a squid represented by both paralarvae and an adult. In many species of squids adults are rarely captured. The figure below shows the remarkable transformation in the shape and size of the eyes of the juvenile and adult.
After the big fish trawl, samples were identified, labelled, photographed and stored. Zooplankton samples were made by the multinet. This is a plankton net hauled vertically in 4 different layers, starting by about 2000 m and one net over the total vertical distance. These nets have a small mesh size (180 microns) and catch only small plankton animals. The catches in the closing nets showed a good variety of species, which were preserved in formaldehyde and will be looked at later when we are ashore again. These animals are small and it is very difficult to identify them on a ship under the microscope due to the ships motion. Specimens were picked out of the open net for genetic studies and we found quite a good representation of the species we expected. In the superficial 0-100 m catch consisted almost exclusively salps (gelatinous zooplankton); the sample was virtually a big tray full of jelly. So, sadly, no other animals were alive in this sample that could be preserved for genetic studies.
At five oclock in the morning the krill trawl came in and brought much excitement again. The trawl was towed from 2000 m to the surface, which was fished in 5 different depth layers. We found a very good representation of deep-sea and midwater fishes. One of the myctophid fishes found was a species belonging in warm waters and never before found so far north. Small transparent medusae (jellyfishes) were found along with big decapod shrimps.
A giant ostracod (pea shrimps, because they are round and look like peas instead of shrimps), Gigantocypris, was found which, instead of the usual 3-5 mm length, is about 15 mm long. This giant species is especially interesting since it also occurs as far south as the Antarctic region. Genetic studies are needed to see whether it really is the same species throughout its range (we think it is different).
Besides the net catches, video recordings were made. These video recordings are particularly important for fragile creatures that may be damaged by conventional net sampling.