>Seas: ca 1-2 feet >Winds 20 knots >Temp -1.5 C ; w/ wind chill –17.5 C >Location: Latitude 63 degrees 42 42’ S; Longitude 57 degrees 22.00 W

Above: A "brooding" starfish (i.e., a mother with babies beneath it). Below: An octopus, about 4-inches long, that "inked" when it was removed from the benthic trawl. (Photo by Susie Balser) Click on images for larger views.

2 December 2004

Today was the first day where we have clearly entered Antarctica. Our first sampling station was in the middle of a field of icebergs. The Salp Group sent out a group of divers to collect gelatinous zooplankton in water that measured –1C. As these holoplanktonic organisms live in a world without walls, they are significantly damaged when collected using nets. The problems of collection are overcome by capturing individuals with hand held jars. Using this collection method, the animals are brought on board in pristine condition and can be immediately used in experiments. Alas, no salps were seen and the overall visibility was reduced by the presence of a bloom of diatoms.

As we steamed around the tip of the Antarctic Peninsula we saw hundreds of icebergs, it lightly snowed, and had our first glimpse of the snow and glacier covered continent. The day’s activities were dominated by collections of benthic animals for studies of population genetics and linking larval forms to their benthic adults. We retrieved a Blake Trawl at ca. 4 p.m. and finished processing tissue samples at 10 p.m. The taxonomic diversity contained in this trawl was astounding. At least three species of pterobranchs brought a smile to the faces of Drs. Balser and Halanych. The echinoderms, as always, were the dominant group in this tow. The sea floor at the sample site was very fine silt, and we found an abundance of burrowing sea urchins (the so-called heart urchins). I am hopeful that the Biology 219 students will recall that these forms have secondarily acquired bilateral symmetry. Interestingly many members of the genus Abatus have deep depressions on their aboral surface that serve as brood chambers. In these forms development is direct and a juvenile urchin emerges from these depressions.

Our "team" finished processing the benthic sample just in time to deploy a plankton net at 10:30 p.m. The abundance of larval forms in our plankton tows has exponentially increased since we left the Drake Passage and we passed off the remainder of the tow to the 12-4 team at midnight. Before we departed for a well-deserved sleep, we did collect larvae of sea urchins, sea stars, a limpet (patellogastropod), worms and more worms, and, for the first time, an ascidian. Once again, let us recall that the benthic ascidians are members of our own phylum (Chordata), but reveal the majority of their chordate characteristics during the larval phase. These "tadpole" larvae possess a notochord, dorsal hollow nerve cord, and post anal tail, while the adult forms lose these characters, but possesses a perforated pharyngeal wall. The tadpole larvae were relatively "simple" and will undergo a rather extensive morphological change at the time they undergo metamorphosis and become affixed to the sea floor. It is during this transformation that some chordate characters are lost and others (e.g., the perforated pharynx) are acquired.