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>Seas: ca 1 foot
>Winds 5 knots
>Temp -1.5 C ; w/ wind chill –2.9 C
>Location: Latitude 62 degrees 08.74’ S; Longitude 57 degrees 32.86 W

A large sea star was the Catch of the Day. Click on image for larger view.

4 December 2004

As you have no doubt noticed, today we have moved the north. The sun is shining and the air temperature has crept above freezing. It really is a rather pretty day.

Our work area is the Bransfield Strait on the southern side of the South Shetland Islands. We had an uneventful plankton tow this morning and we are currently steaming to the site of our first benthic sampling station.

The benthic samples collected yesterday contained several species of "irregular" sea urchins. These are sea urchins that have secondarily developed a degree of bilateral symmetry. They commonly burrow in soft sediments and have a more or less flattened profile to their endoskeleton. What is particularly interesting about these collections was the presence of species that exhibit direct development and brood their young in depressions in the skeleton of females (the so-called marsupium). Contained within these chambers we found a number of different stages of developing embryos and juveniles. These species also produce large eggs (ca. 1 mm diameter) at the cost of a reduced fecundity.

As one might predict, the maternal investment in brood protection should reduce the likelihood of mortality during the development. Sea urchins are not the only echinoderm present in our samples where females provide brood protection. We also collected a number of individuals of a sea star species that were brooding their young beneath their mouth. This species also undergoes direct development, but in this case, the adults are likely not capable feeding while they are holding a brood.

Today I am beginning a series of experiments designed to evaluate the sites of nutrient assimilation and the subsequent translocation of assimilated nutrients by pterobranchs. I will be incubating several specimens in a solution or either iron dextran (a polysaccharide) or ferritin (an iron containing protein). After each incubation period, the specimens will be treated with an acidic potassium ferrocyanide solution to visualize the presence of iron in cells. He change in the distribution of the blue reaction product as a function of time of incubation will provide insight into the patterns of nutrient distribution in these species.

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