20.02.2013 - Marbled and spotted form of Eusirus perdentatus

20.02.2013 (Wednesday). I go up at 09:30.  Weather foggy and windy.  Early in the morning we are into the ice but soon after we are again in open water. I look more carefully at the remaining protective sheet of linoleum of the dredge. It is also damaged and I cannot take the risk to loose it (and to have the bag of the dredge damaged as a consequence). So I have to remove it and replace it as soon as possible. I will have to do in two step, due to the lack of time, but let's go. I start by removing the bolts and nuts. The damaged sheet is removed. I replace it by the sheet of stronger rubber. I make small holes in it for the bolts and start to assemble them. I have not the time to finish. The next trawl arrive on deck.  As for previous benthic stations, we do two close benthic  stations: one around 200 m and one around 450 m. So we sample in the same sector as yesterday but deeper. It gets even more windy than yesterday. When we go out for the Agassiz trawl, we first have the feeling that the net is empty. Actually, the bottom was simply more sandy and all the sediment went through the mesh of the net. As there were also no stones, we only got the organisms. The abundance of the fauna is not huge, but we got a lot of crustaceans, especially Eusirus (several species) and again Ceratoserolis. In the same vein as the case presented yesterday, we get side by side the "marbled" and the "spotted" form of Eusirus perdentatus, which are actually two different (large and spectacular) species. The "spotted form" is actually an undescribed species, as shown in the master thesis of Marie. 

Immediately after the trawl, we use the Rauschert dredge: not the usual one, which is temporarily out of use but the old one, which got into big troubles some years ago and that Henri Robert repared with the very limited material available to him, in using his practical imagination. This dredge looks a bit weird but it works more or less properly. We are working in windier and windier conditions (probably wind force 8). Our buckets are flying and we have to secure them in a corner sheltered from the wind. The catch is of medium quality. In the evening we sort out the material of the trawl and the dredge and after that I finish to repare the first dredge (fixing the last bolts and nuts). 22:05, I see by the window of our lab that we again in the ice. The sky is deep gray and gloomy. A tabular iceberg in the distance also looks quite dark due to the lack of light.

(Cédric)

Wednesday 20.02.2013

An Agassiz trawl is planned for the afternoon. The quantity of the catch is not big but surprisingly very clean. We got used until now to play in the mud but this time, only organisms were brought to the surface. The fine sediment probably got out of the net during the way up. A lot of Eusirus perdentatus can be found again, belonging to the two different chromotypes, one with a marbled red coloration and a spotted one with bright red gnathopods. 

Later in the day, the wind begins to blow very strongly. When we go out again for the dredge, it´s very difficult even to walk around, our buckets are flying away and we have to shelter behind the containers to be able to work more or less properly. It´s quite impressive, I think I never experienced wind of that force before. 

(Marie)

"Eusirus perdentatus marbled form" (65 mm). This is presumably the true Eusirus perdentatus. 

"Eusirus perdentatus spotted form" (75 mm). This is presumably an undescribed species. The colour variations of the two colour morphs exhibit no overlap. The two forms are genetically distinct and exhibit minor morphological differences. The "spotted form" has a slightly larger maximum size, and its maximum of abundance is located deeper.