A recent expedition to one of the deepest places on Earth has discovered one of the most enigmatic creatures in the deep sea: the 'supergiant' amphipod.
Similar to shrimps, amphipods are a type of crustacean particularly common in the deep sea, and are found in greater numbers the deeper you look. Typically deep sea amphipods are two to three centimetres long with the exception of the slightly larger 'giant' amphipod found in Antarctica. The supergiants dwarf the Antarctic giant.
They were discovered in the Kermadec Trench, north of New Zealand, by scientists from the University of Aberdeen and the National Institute of Water & Atmospheric Research (NIWA), who led a joint UK/New Zealand expedition to the area. Also aboard NIWA's research vessel, the 'Kaharoa', were scientists from the Museum of New Zealand/Te Papa Tongarewa and Whitman College, USA.
Using specially designed ultra-deep submergence technology, the team deployed a camera system and a large trap to depths ranging from 6,900 to 9,900 metres. The team was aiming to recover specimens of the deep-sea snailfish, which had not been captured since the early 1950s but had been photographed previously by the team at approximately 7,000 metres depth. The trap managed to capture seven specimens of the snailfish. However, on further inspection of the trap, the team noticed that amongst hundreds of 'normal' amphipods lay several that were 10 to 14 times larger than any of the others.
"At the moment the traps came on deck we were elated at the sight of the snailfish as we have been after these fish for years," said voyage leader Dr Alan Jamieson from Aberdeen University's Oceanlab. "However, seconds later I stopped and thought 'what on earth is that?' whilst catching a glimpse of an amphipod far bigger than I ever thought possible."
The new sightings and specimens of the supergiant represent both the biggest specimen ever caught (28 centimetres long) and the deepest they have ever been found (7,000 metres deep).
"For such a large and conspicuous animal to go unnoticed for so long is just testament to how little we know about life in New Zealand's most deep and unique habitat," said Dr Ashley Rowden from NIWA.
"The surprising thing here is that we have already been to this deep trench twice and never come across these animals before," added Dr Jamieson. "In fact a few days after the discovery we deployed all the equipment again on the same site and we failed to photograph or capture a single supergiant; they were there for a day and gone the next".
The challenge for the team now is to determine whether these new samples are the same species as those from Hawai'i and to try and establish why, out of the hundreds of species of deep-sea amphipods, these ones have evolved to be so large. The supergiant and the fish specimens are current residing in Wellington, New Zealand until after the team's next expedition in February.
