>Waves=15 feet >Temperature 7C >Wind speed 30 knots

24 November 2004

We woke this morning with no land in sight. The sea condition were less than optimal – 15 foot seas and 35 knot winds. Those venturing onto the fantail to work were tethered to the ship and were constantly doused by the waves. Although these weather conditions have slowed out progress, we will complete sample two times each the organisms that reside in the water column (especially planktonic larvae) and those that are sessile on the sea floor by midnight tonight.

Invertebrate larvae were not very abundant. Larvae of polynoid polychaetes (w/ elytra) and gastropod mollusks (caeonogastropods) were the most abundant, but even these forms were not very common.. What was astounding about the morning sample was the presence of a tremendous amount of phytoplankton (planktonic photosynthetic organisms). The color of the sample was literally dark green and the abundance of plant cells greatly exceed the zooplankton (animal plankton). Blooms of phytoplankton are not unusual in these waters this time of the year. Why might this be?

The benthic samples were spectacular. The diversity of the fauna of the sea floor was remarkable. All six extant classes of echinoderms were present. We found large keyhole limpets, enormous colonial tunicates and tunicate that remains attached to the sea floor via tethers. All of these pale when compared to the enormous number of pterobranch hemichordates. As some of us remember, the Pterobranchia are a group of hemichordate worms which live in tubes, are colonial, and bear a coelom filled tentacular crown. These members of the genus Cephalodiscus were large (visible without the aid of a microscope) and formed colonial clumps the size of one’s fist. Absolutely remarkable – this is the first time I have seen living pterobranchs.

Pterobranchs are of interest to all interested in the evolution of the phylum Chordata (our own). Members of this class and the class Enteropneusta together form the phylum Hemichordata, a group that was thought to be the sister taxon of the Chordata. Recent studies of gene sequences has resulted in a new interpretation of the phylogentic position of the Hemichordata. Now these “half chordates” are proposed to be more closely related to the echinoderms (sea stars etc.) than they are to the Chordata. These are radically different hypotheses about the relatedness of groups. Dr. Susie Balser (IWU) is collecting specimens of Cephalodiscus in hopes of addressing questions about the relatedness of these three major Deuterostome phyla (Chordata, Echinodermata, Hemichordata).

Off to work, we are on a rotating 4:8 work cycle and my bell is about to ring again.