ALBERT

Description: 〈span〉〈div〉Abstract〈/div〉The majority of sediment-dwelling foraminifera are thought to be deposit feeders. They use their reticulopodia to gather sediment with associated algae, organic detritus, and bacteria. Uptake of diatoms by foraminifera have been observed but rarely quantified. We measured the clearance (gathering) rate and ingestion rate of diatoms by the common benthic foraminifer 〈span〉Quinqueloculina seminula〈/span〉 using 〈span〉Nitzschia closterium〈/span〉 as prey under laboratory culture conditions. Grazing experiments were performed to evaluate the effects of temperature (at 12, 15, 18, 21, and 24°C) and food availability (10 to 800 cells mm〈sup〉−2〈/sup〉) on uptake rates of diatoms. The clearance rates, estimated from the disappearance of food items, were variable (0.59–4.4 mm〈sup〉2〈/sup〉 foram〈sup〉−1〈/sup〉 h〈sup〉−1〈/sup〉) and did not show a clear relationship with food availability. The maximum clearance rates increased from 1.80 ± 0.21 to 2.69 ± 0.32 mm〈sup〉2〈/sup〉 foram〈sup〉−1〈/sup〉 h〈sup〉−1〈/sup〉 when temperature increased from 12 to 18°C and decreased to 2.28 ± 0.25 mm〈sup〉2〈/sup〉 foram〈sup〉−1〈/sup〉 h〈sup〉−1〈/sup〉 at 24°C. Ingestion rates varied from 1.0 to 43 × 10〈sup〉3〈/sup〉 diatoms foram〈sup〉−1〈/sup〉 h〈sup〉−1〈/sup〉, following a hyperbolic response to food concentrations at all experimental temperatures. The maximum individual ingestion rates increased from 842 ± 180 to 1648 ± 480 (mean ± SE) cells foram〈sup〉−1〈/sup〉 h〈sup〉−1〈/sup〉 and then decreased to 316 ± 54 cells foram〈sup〉−1〈/sup〉 h〈sup〉−1〈/sup〉 as temperature increased from 12 to 24°C. Experimental results revealed that 12–18°C was the optimal temperature range for 〈span〉Q. seminula〈/span〉 feeding for specimens adapted to local conditions. Our study indicates that 〈span〉Q. seminula〈/span〉 plays an ecological role by feeding upon benthic diatoms in marine benthic ecosystems.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉We carried out a series of experiments to evaluate the efficiency of preserving DNA from porcelaneous foraminifera (〈span〉Quinqueloculina〈/span〉 spp.) and a second set to assess the effect of Rose Bengal staining on molecular processing. The first experimental setup assessed three methods of DNA preservation (air-drying, freezing with or without seawater, and Guanidine lysis buffer treatment with or without EDTA (Ethylenediaminetetraacetic acid)). Our study produced the following results: 1) there were no significant differences in DNA preservation when samples were air dried across a range of temperatures (20–120°C); samples frozen at −20°C appeared better preserved than at those frozen at –80°C, and freezing without seawater appeared to produce better preservation than with seawater, though differences in freezing treatments were not significant (〈span〉p〈/span〉 〉 0.05); samples in Guanidine lysis buffer with EDTA and stored at –20°C were well preserved (〈span〉p〈/span〉 〈 0.05); 2) sometimes, DNA was successfully extracted from samples stained with Rose Bengal. We recommend Guanidine lysis buffer with EDTA, stored at –20°C for up to six weeks, as the best protocol for preservation of DNA from porcelaneous foraminifera.〈/span〉