By Kevin Kocot |
Currently we are breaking ice and making our way westward. The region we are approaching is particularly interesting to some of the biologists on board because very little biological sampling has been conducted in this part of the Weddell Sea. The Genetics Team is a group of biologists who study diverse animals using DNA-based tools. We have experts on fish, brittle stars, molluscs, corals, and sponges and are also collecting specimens of other animals for other colleagues not on board. The tools of our trade are the Agassiz trawl (see photo 1) and bottom trawl. These instruments are basically large metal frames with a net attached that are lowered out behind the ship and towed for about ten minutes to collect benthic animals (animals living on the sea floor). When the net is pulled back to the surface it can be full of animals, which are released onto the deck and quickly sorted into buckets of cold sea water. Sometimes the net fills up with mud and this mud must be sieved to reveal the animals inside (photo 2).
Back in the lab, specimens are given a unique identification number and photographed with a scale (for example the sea star on photo 3). Small tissue samples are then preserved in ethanol or another molecular biology fixative for genetic work and the rest of the specimen is preserved in formalin for morphological/anatomical study. When we return to our laboratories, we will conduct a number of different types of studies. For example, population genetics is the study of the genetic diversity among populations of an organism and can help us understand if different populations of an organism are interbreeding or isolated. Some species that have larvae that swim/float in the water column before settling on the bottom and turning into an adult may be genetically uniform across vast distances, even all the way around Antarctica. On the other hand, organisms that hatch out of the egg as a miniature version of the adult and lack such a dispersal phase may have many, genetically different populations that can be so genetically different that they can be considered separate species. Understanding the genetic diversity among populations of an organism and how this diversity is structured with respect to geography (phylogeography) is important for
understanding the potential effects of climate change on biological diversity and for making management decisions.
Some particularly interesting animals will be used for high-throughput DNA sequencing. This type of work allows us to determine all the genes present in an organism or which genes are “turned on” in an organism during a particular developmental stage or in a particular tissue. Taken together, this information can help us understand how the myriad of different animal forms have evolved.
In addition to conducting genetic work, some of us are also conducting classical taxonomic work. For example, there are no acorn worms (Hemichordata) described from Antarctica, but we have collected two specimens of an as yet unnamed species (see photo 4). Acorn worms are interesting from an evolutionary perspective because they are (distantly) related to humans and other animals with a backbone (as evidenced by their fish-like gill slits). We have also discovered at least two new species of mollusc, including a very strange worm-like species that lives inside of sponges. As we continue west, we hope to be able to sample areas that have been the subject of little study and expect to continue to make exciting discoveries.
Best regards from Polarstern,
Kevin Kocot, Uni Alabama & Alabama Museum of Natural History