The Antarctic marine environment is characterized by extreme seasonality in primary production, and herbivores must cope with a prolonged winter period of food shortage. In this study, tissue mass and biochemical composition were determined for various tissues of the bivalve Laternula elliptica (King & Broderip) over a 2 yr period, and its storage and use of energy reserves were investigated with respect to seasonal changes in food level and water temperature. Total ash-free dry mass (AFDM) accumulated rapidly following phytoplankton blooms (with peak values immediately before and after spawning) and was depleted considerably during the spawning and winter periods. Most of the variation was in the muscle, gonads and digestive gland. Spawning peaked in January and February and caused considerable protein and lipid losses in the muscle, gonads and digestive gland. In winter (March to August), the muscle and digestive gland lost considerable mass, while gonad mass increased; this suggests that the muscle tissue and digestive gland serve as major energy depots for both maintenance metabolism and gonad development in winter. There were also marked year-to-year differences in the seasonal patterns of mass variation and reproduction. Overall, the relative and absolute tissue-mass values were positively correlated with chlorophyll concentration, and were not related to water temperature; thus, for the first time, this study clearly shows that food is an important factor governing growth and gonad maturation in this bivalve. It is also noteworthy that protein, constituting ~75% of AFDM, served as the major energy reserve throughout the study, closely following the AFDM variation. In particular, during the winter months, protein comprised >60% of AFDM loss, while lipids and glycogen served as minor (< 20% each) reserves. Protein loss was most substantial in the muscle tissue, which comprised half of the body tissue. Thus, protein use, with muscle tissues as a depot for protein reserves, may be a result of selective pressure on Antarctic marine herbivores undergoing a prolonged period of food shortage in winter.

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Generic boundaries among the genera Cheilosporum, Haliptilon, and Jania-currently referred to the tribe Janieae (Corallinaceae, Corallinales, Rhodophyta)-were reassessed. Phylogenetic relationships among 42 corallinoidean taxa were determined based on 26 anatomical characters and nuclear SSU rDNA sequence data for 11 species (with two duplicate plants) referred to the tribe Corallineae and 15 species referred to the tribe Janieae (two species of Cheilosporum, seven of Haliptilon, and six of Jania, with five duplicate plants). Results from our approach were consistent with the hypothesis that the tribe Janieae is monophyletic. Our data indicate, however, that Jania and Haliptilon as currently delimited are not monophyletic, and that Cheilosporum should not be recognized as an independent genus within the Janieae. Our data resolved two well-supported biogeographic clades for the included Janieae, an Indian-Pacific clade and a temperate North Atlantic clade. Among anatomical characters, reproductive structures reflected the evolution of the Janieae. Based on our results, three genera, Cheilosporum, Haliptilon, and Jania, should be merged into a single genus, with Jania having nomenclatural priority. We therefore propose new combinations where necessary of some species previously included in Cheilosporum and Haliptilon.

A new mechanism for the abiotic production of molecular iodine (I2) from iodate (IO3 –), which is the most abundant iodine species, in dark conditions was identified and investigated. The production of I2 in aqueous solution containing IO3 – and nitrite (NO2 –) at 25 °C was negligible. However, the redox chemical reaction between IO3 – and NO2 – rapidly proceeded in frozen solution at −20 °C, which resulted in the production of I2, I–, and NO3 –. The rapid redox chemical reaction between IO3 – and NO2 – in frozen solution is ascribed to the accumulation of IO3 –, NO2 –, and protons in the liquid regions between ice crystals during freezing (freeze concentration effect). This freeze concentration effect was verified by confocal Raman microscopy for the solute concentration and UV–visible absorption spectroscopy with cresol red (acid–base indicator) for the proton concentration. The freezing-induced production of I2 in the presence of IO3 – and NO2 – was observed under various conditions, which suggests this abiotic process for I2 production is not restricted to a specific region and occurs in many cold regions. NO2 –-induced activation of IO3 – to I2 in frozen solution may help explain why the measured values of iodine are larger than the modeled values in some polar areas.