Invasion of the Comb Jellies!

We passed a long quiet night with the Scanfish in the water,

View from the bridge at night.

View of the stern from the bridge at night.

collecting data, reminiscing about cruises past, and of course, hitting the ice cream freezer hard.  Mapping the conditions is not the most exciting thing we do in terms of activity, but it’s important because we were able to discern that near the mouth of the Rapahannock River the oxygen in the deep water rose to about 2 mg per litre, which is one definition of the cutoff value for hypoxia. Up near the mouth of the Choptank deep water dissolved oxygen was almost zero, and what that really means for us is that we can revisit the same two stations we visited in May to make a nice comparison between cruises and stations.

But I digress. The big news is the jellies.  Just standing on the deck and looking down we could see the comb jellies, known by their scientific name Ctenophores. These animals are not the same as the sea nettles, in fact they are in an entirely different phylum and have a very different physiology.  While the sea nettles are characterized by their stinging cells, or nematocysts, ctenophores have coloblast cells to capture prey, which are sticky rather than stingy.  Stingy nettles, sticky ctenos. They are called ctenophores because ‘cteno’ means “comb”, and they are called that because of their rows of comb-like structures with tiny hairs that they wave to swim. There are plenty of beautiful pictures on the internet of ctenophores swimming with their iridescent combs refracting light into rainbow colors.  I don’t have the capacity to take pictures like that on this trip, but here are some pics of our jelly net and a sample jar with a jelly…

jelly net

Retrieving the closed jelly net.

jelly net codend

The codend of the jelly net, full of ctenophores.

jar with ctenophore

Sample jar containing a ctenophore.

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About planktoneer

I'm a zooplankton ecologist who studies how individual behaviors and variability affect populations of copepods in marine and estuarine systems.
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