Monday, 8 September 2008

Hey, this looks familiar...!

Yesterday we went past Toalanaro again - the place where we swapped crew about a week or so ago. I thought the coastline looked familiar... Seems strange to have gone so far and to have ended up in exactly the same place!

Essentially, we had to rush to Toalanaro because of the bad weather early in the trip, and then rush back the way we had come in order to do the work that we needed to do on that section of coastline; yesterday we completed it and started the survey along the East coast of Madagascar - an area that is very poorly surveyed from an oceanographic point of view, so we're very interested to see what our detailed investigations will show!

Yesterday, I awoke to the sound of what my brain thought was the abandon ship signal. It *was* the abandon ship signal, but it turns out they were only testing the system. Not a great start to the day. Then it was into a whole load of trawling.

On one of the trawls, I noticed a paper nautilus, Argonauta sp., whilst we were sorting. It looked rather unhappy with life, having been more or less separated from its "shell"; I put it in a bucket (which it immediately filled with ink - I washed this away with plenty of water and left the water running). By the time we had finished sorting the catch, it had reattached itself. Paper nautiluses are actually pelagic octopi; the females secrete this "shell" from their egg-glands, whilst the males are comparatively dwarfs and have no shells. This shell is not analagous to the shell of other molluscs - it is a new evolutionary adaptation. Unfortunately, the photos Bradley took didn't come out that well (the macro on his camera isn't easy to use, nor particularly macro!), but I have attached a few here. I think they're quite cute, despite all the tentacle-y sliminess! I suspect, based on the darkness of the shell, it may be Argonauta bottgeri. For more pictures of argonauts, click here. If you look carefully at the bucket picture, you can see the syphon the animal uses to jet-propel itself around sticking out of the lower part. Bradley got squirted in the face when he tried to look at it earlier; clearly they can pump water out of there quite hard! After we took a few quick pictures, I released it back into the sea.

In a later trawl, we caught a sea catfish. These animals have venomous spines and considering my unfortunate history with venomous fishes, I wasn't too keen to have a repeat performance - miles out to sea. Nevertheless, we had to weight it, and I thought some photos would be a good idea. Identifying it proved to be tricky; the key called for examining the inside of the mouth. Clearly, whoever designed that key didn't think they'd be holding a large, live, struggling animal with stout, venomous spines flopping around. I gave that character up as a bad idea; the other part of the key couplet suggested the back of the head was fairly rough. Well, it looked fairly bony to me (as opposed to "covered in muscles"), so I therefore took it to be Ariodes dussumieri. It also went back over the side. We even managed to rescue a few thornfishes and horse mackerel (Terapon theraps and Trachurus delagoa), which recovered nicely in one of the JESRT plastic buckets.

Oooh, the name has changed - I just tried searching for it on Fishbase, and it seems this sea catfish species is now called Plicofollis dussumieri. Latin (scientific) names are often in a state of flux as more research is carried out. Taxonomy is partly a historical detective story (uncovering what has been written about the species you're working on - often in other languages, even Latin sometimes - sometimes with very vague descriptions), partly measuring and observing a hell of a lot of animals (and the analysis of that data) and partly (though I hate to say it) a "gut feeling" thing. Biology isn't neat and tidy like chemistry and physics!

Pinning down exactly what is a species is harder than you might think - and because animals are still evolving, they are not going to be fixed forever! But the pigeonhole of a "species" is certainly very useful in terms of doing research and trying to understand what is going on in an ecosystem. New genetic tools are re-arranging a lot of what we thought we knew about taxonomy. If you look very carefully, the picture on the left has at least 5 species (somewhat) visible in it, but the overwhelming majority is horse mackerel.

Of course, all this flux and uncertainty makes preserving voucher specimens (preferably with an associated DNA sample these days) very valuable. You may think you know what species you're working on, but what happens if someone finds out there are actually two species? Which one was all your work done on? How about if other people want to verify in three hundred years time the work you did, and what species you were referring to? (I regularly used literature [mainly in French, one in Latin] from the late 1700s and early 1800s when I was doing some taxonomic work). The descriptions were not always very good. Putting an example of what you think you're working on in a recognised biological collection and then referring to it in your publications is a very, very good idea.

Preserving specimens in a recognised collection also means that there is a "library" of material that taxonomists can do their work on. As nice as it is to go out there and hunt down elusive species, you often have neither the time nor the funding to do so; carefully preserved specimens are the bread and butter of taxonomists.

We're currently here, steaming along at around 9 knots with nearly 5 kilometers of water under the ship!

Images courtesy Bradley Flynn (3) & James Stapley (1).

Comments: Post a Comment

<< Home

This page is powered by Blogger. Isn't yours?

Subscribe to Posts [Atom]