Polar cod embryotoxicity to crude oil water soluble compounds

Exper­i­ment Com­plet­ed: Three days ago, we com­plet­ed our exper­i­ment. It was not with­out a lot of work and some trou­bles on the way.

After a mass mor­tal­i­ty that seemed pret­ty much out of con­trol in all our incu­ba­tors and not at all dose relat­ed we were left with too few sam­ples. After bare­ly a week of expo­sure (start of gas­tru­la­tion), we decid­ed over a week-end (it always hap­pens then) to start from scratch again!!!

Not with­out a lot of doubts and ques­tions: Since our rock oiled sys­tem had been run­ning for a week already, con­cen­tra­tion is the water were already very dilut­ed for this new start. Would we see any effects at all? Were we in such low lev­els that even sub-lethal effects would be tricky to see?

We need­ed to through away (well fix…) all the remain­ing eggs of exper­i­ment 1, to pre­pare the incu­ba­tors for the new batch­es. But the fish left in our tanks seemed almost all done with spawning…would we find enough of then for a new start? Were we going to throw all away and not get enough eggs and sperm?

We took our courage “under our arms” and just did it!

New strat­e­gy: Obvi­ous­ly the egg qual­i­ty was very dif­fer­ent from female to female…basically spoil­ing all the incu­ba­tors if you mixed all the eggs of all avail­able females togeth­er. We thus sep­a­rat­ed the eggs from incu­ba­tor to incu­ba­tor, hop­ing that at least some of the eggs would be of good qual­i­ty and not just die as soon as the devel­op­ment would reach a lit­tle more com­pli­cat­ed stage than division…



And it worked, not with­out the (almost) loss of 2 out of 5 egg batch­es. But so far the data is real­ly nice…not mor­tal­i­ty from the treat­ment, but clear sub-lethal effects (see fig). The pic­ture shows bach­e­lor stu­dent Antoine and col­league Mar­i­anne strip­ping polar cod on sun­day evening!

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The Fig­ure shows the lar­va from one batch of eggs (out of 5) at the end of the exper­i­ment (lar­va left after all pre­vi­ous sam­plings, etc). The blue bars are the per­cent­age lar­va free swim­ming in the incu­ba­tors, the red are those (still alive) mal­formed and lay­ing on the bot­tom of the incu­ba­tor. The num­bers on the bars are the total count of lar­va per incubator.

Click on this link and you will see the heart beat of our eggs: embry­otox



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