Polarstern / CAML expedition: amphipods captured !
The mysterious Eusirus
© C. d'Udekem d'Acoz / Alfred Wegener Institute
A traps-dedicated evening ! Christian prepares his fish traps to obtain the specimens he needs for his physiology research. Captured fish will be put in an aquarium for several days to recover from the stress of being caught. They will then be transferred to a "chamber", where a sophisticated device will measure their blood flow rate in various organs, at varying temperatures, with the aim to better understand their sensitivity to high temperatures. This is typically fundamental research even if, with climate change, it could unfortunately find some application in coming decades.
Secured on a metal frame, equipped with a weight and buoys able to cope with the high pressure at the bottom, the baited traps were put at 800 meters depth. Other smaller traps aimed at catching amphipod crustaceans were added to the frame. Once on the right spot, Christian sent an acoustic signal from an hydrophone located on the surface to release the weight and allow the whole system to come back up. Spotted thanks to its bright yellow buoys, the frame is hauled back on deck by the crew.
Time to open the traps! For Christian and his team it's a disappointment: no fish this time. But for Henri and Cedric, what a treat! Like they hoped and considering the depth, the big fish traps have attracted about 100 amphipods of huge size, at least huge for their group. The most numerous are the "Eurythenes gryllus", effective swimmers with a length of 10 cm and a bright orange color. Found worldwide under 2000 meters, this species requires a temperature not exceeding 5°C: it can be found closer to the surface only in polar regions. But our "amphipodologists" also quickly discovered ten specimens of another species, a superb pink and red-legged "Eusirus". After careful examination Cedric expresses his verdict: it could well be a new species!
