Thursday 17 January 2008 à 15:16

A day without end (through the eyes of Team Leader Catherine Ozouf).

Par Sophie Mouge. Correspondent aboard the Aurora Australis

23h30: The alarm clock rings. I jump out of bed, boot up the computer and rush to the shower: a great way to wake up!

Catherine does her hair in the bathroom.

I have ten minutes to wash and dress, and a quarter of an hour to pick up all the e-mail that accumulated during the evening. The urgent ones will be addressed later between trawls.

00h00: I go down to the wet lab to see what’s new. When sorting is underway, I stay and help with the fastidious operation.

Bernard and I sort the benthos in the wet lab.

But often, it’s a chance for everyone to enjoy a hot drink and a light snack while we exchange comments on what has been collected in the past twelve hours. Samuel and Bertrand give me the data necessary to follow up for the next shift.
Work is carried out by two 4-man teams working twelve-hour shifts, or watches, from midnight to noon and from noon to midnight.

Between 1h00 and noon: When a drag net arrives on the trawl deck, its contents are sifted by Fred and Marc, assisted by Australian colleagues. The fish are rinsed and quickly placed in a container of running sea water before being analyzed, or put in an aquarium for later treatment.

You said “fish”? Guillaume Lecointre, one of our CEAMARC correspondents at the Museum, would tell you that “fish” is a culinary term not a scientific one. It designates several distinct groups with no direct kinship. The two main ones are: Chondrichthyes, cartilaginous fish like rays and sharks, and Teleosts, bony fish like trout and icefish. In truth, teleosts are more closely related to mammals than they are to chondrichthyes. In other words, a trout or icefish is more closely related to human beings than to sharks!

With Fred’s assistance, I am essentially occupied with the fish, just lending a hand to sort the benthos when there is time left between trawls.
The fish are subject to a number of measurements and samples before being conserved in formol. We work in pairs: one with hands in the water and the other with dry hands!

As to the CEAMARC benthos team, each of the ichthyologists on board works not just with his team but also with other specialists, who will later study the taxonomy, phylogeny and ecology of the collected materiel.

7h30: short break: In 10 minutes, we take turns by twos to eat breakfast. When we fail to make the official mealtime (which deprives us of eggs and bacon!), we catch up with leftovers and bread and butter. There is always something to snack on and a way to fix hot beverages.

Sometimes the trawls come so fast one after another that we do not have time to finish work on the fish between two operations. In such a case, Marc leaves Bernard to finish sorting the benthos and comes to assist us.

Noon: We leave the area and give way to the day shift that arrives a few minutes beforehand in order to find out about the tasks remaining to be done. We hurry to eat lunch before meal service ends at 12h30. Every day, we go over plans for the operations for the coming 24 hours, during lunch or over coffee with the mission leader. Sometimes, we go up together to the bridge to look at the bathymetric charts and to consult the satellite data.

13h00: For me, a second day begins with a cup of very strong coffee to keep my eyes open. I normally move to Laboratory 2 where the chromosome preparations are carried out on the fish kept in the aquariums. To save time, Stefan and I organize a real assembly line, handling the same specimens that we use for our respective purposes.

Stefan and I work together in a tight laboratory.

I am a cytogeneticist, that is, I have been studying the chromosomes of teleosts and particularly Antarctic species for about twenty years.

How do you visualize the chromosomes of a fish?
The dissection of a fish provides access to certain organs that are rich in dividing cells, like the spleen and the kidney.

I take spleen and cephalic kidney samples from a Notothenioid fish.

The cells from these organs are dissociated then we let them multiply in a culture medium for several hours. The process of cellular division is stopped at a stage in which the chromosomes are highly visible (metaphase) then the cells are split to recover the chromosomes that are stained so they can be observed with a microscope.

My work aims to identify the chromosomal alterations that are produced in the course of the diversification of Antarctic species of Notothenioids. These alterations can affect the number or the arrangement of the chromosomes (karyotype) as well as their fine structure (localization of genes or particular sequences in the DNA of which they are made up).

Microscopic observations of chromosomes carried out on 3 Notothenioids with red blood (presence of the globin gene but in pairs of different chromosomes) and one Notothenioid without hemoglobin - icefish (absent the globin gene). The green arrow points to the globin gene.

I am studying the tempo of their appearance in order to understand how genomes evolve over time. For example, in the genus Trematomus, chromosomal diversification is massive and is produced over a period of about 3 million years, which is short.

17h00: I write my e-mails, I edit the mission accounts and reports, discuss the log with Sophie, etc.

I work beside Romain in the conference room.

A stealthy trip to the bridge allows me to contemplate the immense iceberg that we are slowly approaching. It measures 38 km by 18 km.

Immense iceberg in the distance.

18h00: Now it’s time to think about sleeping. The night will be short but fortunately I do not need much sleep.
And from time to time, I take an afternoon off to recuperate without karyotypes!

To go further...
There are several methods for preparing the chromosomes.

All of them in the end obtain cells in the metaphase stage of cellular division, when the chromosomes, distributed on the equatorial plate, are best separated from one another. For this campaign, I am essentially using a cell culture protocol. I choose tissues likely to produce a great number of cellular divisions: the cephalic kidney, in which lines of blood cells are generated, and the spleen, in which the lymphocytes divide. I put the cells in suspension in special beakers filled with a synthetic culture medium, enriched with serum, to which I add a mitogenetic product (concanavalin A), and I cultivate them in an incubator at +2°C. After 5-6 days, I add colchicine to the beakers to stop the cells at the metaphase stage and I let it act for at least 6 hours. The colchicine breaks the microtubules and keeps the chromosomes on the equatorial plate from migrating toward the poles. Then I collect the cells with centrifugation and transfer them into a hypotonic liquid (KCl) where osmotic shock breaks their walls and frees their contents. The cellular suspension is again centrifuged and the hypotonic liquid replaced with a fixator (a mixture of methanol and acetic acid) before being spread on microscope slides, stained and observed at high magnification. The karyotype is produced from several photographs of the metaphases. The chromosomes are classified by pairs and by category as a function of the position of the centromere (metacentric, telocentric, etc.). The number and the pattern thus established define the karyotype of a species.
With these chromosomal preparations, it is possible to localize genes by the fluorescence in situ hybridization method.



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