On the Biology of an Intertidal Chthamalid (Crustacea, Cirripedia) from the Chukchi Sea

A Pacific-boreal species, Chthamalus dalli occurs in the narrow intertidal zone near Cape Thompson, Alaska. Diatoms and filamentous green algae, but no other animals, were associated with the barnacles, which apparently survive the winter frozen in the ice foot. Growth is less than in southern species, but continues for five or more years; maturity is reached in two years and breeding can occur at a water temperature of 6C. There appears to be only a very slight cold adaptation, shown by cirral activity, compared with C. dalli from Southeast Alaska and southern California.Sur la biologie d'un chthamalide intertidal (Crustacea, Cirripedia) de la mer de Tchoukotsk. Près du cap Thompson, Alaska, on trouve dans la zone intertidale l'espèce pacifique-boréale Chthamalus dalli. A part quelques algues éphémères, les autres organismes sont absents de la zone intertidale : la cirripède en question passe l'hiver gelée dans le pied-de-glace. La croissance, étudiée sur les anneaux de la coquille, semble plus lente que dans des localités plus méridionales, mais dure cinq ans ou plus : la maturité est atteinte en deux ans et la reproduction a lieu à une température de l'eau de mer de 6ºC. La comparaison entre les courbes de l'activité cirrale et de la température montre un léger déplacement latéral (adaptation au froid) par rapport à la même espèce dans le sud-est de l'Alaska et le sud de la Californie.Les auteurs discutent de l'absence de l'espèce boréale-arctique Balanus balanoides et concluent que pour les conditions hydrographiques existantes, la période de reproduction estivale plus longue chez C. dalli a pu lui donner un avantage sur B. balanoides dans la colonisation de l'est de la mer de Tchoukotsk

Chemoautotrophic Microbial Mats in Submarine Caves with Hydrothermal Sulphidic Springs at Cape Palinuro, Italy

Observations were made on the distribution, morphology, and chemoautotrophic potential of microbial mats found in submarine caves of dolomitized limestone which contain hydrothermal sulphidic springs at Cape Palinuro, Italy. The distribution of microbial mats is closely associated with the flow of hydrothermal fluid from springs whose activity is intermittent and initiated during low tide. Fluid emitted from active springs in the Grotta Azzurra has a maximum temperature of 24.6°C and is enriched in dissolved sulfur species (H2S, S2O3 2−) and dissolved gases (CH4, CO2). However, it is depleted in NaCl and dissolved O2, in comparison with ambient seawater. This fluid is less dense and rises above the ambient seawater to form a visible thermocline and chemocline separating both layers in the submarine caves. Microbial mats were attached to rock surfaces immersed in fluid above the chemocline and were differentiated into brown and white forms. Brown mats were composed of trichomes (4.2 ± 0.1 μm and 20.3 ± 0.7 μm in diameter) resembling the calcareous rock-boring cyanobacterium Schizothrix and clusters (6 μm in diameter) of sarcina-like cells morphologically resembling methanogenic bacteria. White mats were composed of attached filaments resembling Beggiatoa (19.3 ± 0.5 μm, 39.0 ± 1.7 μm, and 66.9 ± 3.3 μm in diameter) and Thiothrix (4.2 ± 0.2 μm in diameter). Flexibacteria (\u3c1 μm in diameter) were common to both mats. Beggiatoa-like filaments were morphologically similar to those attached to rocks and the byssal threads of mussels from Lucky Strike vent field on the Mid-Atlantic Ridge. Morphological comparisons were also made with typical gliding Beggiatoa from shallow seeps in Eckernförder Bucht, Baltic Sea. White mats displayed chemoautotrophic fixation of CO2 under relatively well-oxygenated laboratory conditions (maximum rate 50.2 nmol CO2/mg dry wt/h) using internal S0 or possibly S2O3 2− as electron donor. Photosynthesis may be limited in the Grotta Azzurra by insufficient illumination (6.3 × 10−7μ einsteins/c

Unusual fatty acid composition of storage lipids in the bresilioid shrimp Rimicaris exoculata couples the photic zone with MAR hydrothermal vent sites

Lipid and stable carbon isotope analyses of Rimicaris exoculata, the dominant bresilioid shrimp found at the MAR (Mid-Atlantic Ridge) vent sites, have indicated that these animals possess a highly unusual storage lipid composition. The dominant neutral lipid classes, triacylglycerols and wax esters, contained very high levels of polyunsaturated fatty acids (PUFA, up to 89% of neutral lipid fatty acids). Gas chromatography isotope ratio mass spectrometry (GC-IRMS) analysis of the PUFA from neutral lipid gave d13C (v-PDB) values of -17.6 to -27.1[per thou], which is within the range expected for a photosynthetic origin for these compounds. Fatty acid analyses of bacterial/detrital material collected from the vent sites contained only very low amounts of PUFA. It is clear from these findings that R. exoculata has evolved a highly specialized lipid metabolism which allows it to store substantial amounts of PUFA during its early planktotrophic life stages. These PUFA reserves will be subsequently mobilized to enable growth and maturation of the shrimp on return to a suitable vent site and are therefore an important factor allowing R. exoculata to inhabit deep sea vent ecosystems

Tackling the Sulfide Gradient: A Novel Strategy Involving Marine Nematodes and Chemoautotrophic Ectosymbionts

The Stilbonemutinue (marine free-living nematodes) arc remarkable for cctosymbiotic bacteria, which cover the greatest part of their body in a highly ordered and species specific pattern. Using SEM we describe the main types of symbiotic cover and give evidence for the role of the bacteria in the nutrition of their host on the basis of stable carbon isotope ratios. In experimental systems the worms migrated repeatedly across a sulfide gradient during 12 h when sulfide concentrations were low, but stayed above the sulfide maximum at high concentrations. The migration across the chemocline exposes the symbionts alternately to reduced sulfur compounds and oxygen; this constitutes an alternative strategy to the ventilation/circulation systems in symbiotic macrofauna from sulfidic habitat