Genetic structure of Octopus minor around Chinese waters as indicated by nuclear DNA variations (Mollusca, Cephalopoda)

Octopusminor is an economically important resource commonly found in Chinese coastal waters. The nuclear gene (RD and ODH) approach of investigation has not reported in this species. Rhodopsin (RD) and octopine dehydrogenase (ODH) genes were used to elaborate the genetic structure collected from eight localities ranging from the northern to the southern coast of China. In total, 118 individuals for the RD gene and 108 for the ODH were sequenced. Overall (RD and ODH) genes resulted in high (0.741±0.032; 0.805±0.038) haplotype and low nucleotide (0.01261±0.00165; 0.00747±0.00086) diversity. Molecular variance displayed higher values among the populations and lower values within the population where the fixation index FST denoted 0.880 and 0.584 in RD and ODH genes respectively. The Dongshan population clustered separately in a phylogenetic tree as in the haplotype networking assessment. The current data suggests that the Dongshan population needs separate management.

Changes to coral health and metabolic activity under oxygen deprivation

On Hawaiian reefs, the fast-growing, invasive algaeGracilaria salicorniaovergrows coral heads, restricting water flow and light, thereby smothering corals. Field data shows hypoxic conditions (dissolved oxygen (DO2) < 2 mg/L) occurring underneath algal mats at night, and concurrent bleaching and partial tissue loss of shaded corals. To analyze the impact of nighttime oxygen-deprivation on coral health, this study evaluated changes in coral metabolism through the exposure of corals to chronic hypoxic conditions and subsequent analyses of lactate, octopine, alanopine, and strombine dehydrogenase activities, critical enzymes employed through anaerobic respiration. Following treatments, lactate and octopine dehydrogenase activities were found to have no significant response in activities with treatment and time. However, corals subjected to chronic nighttime hypoxia were found to exhibit significant increases in alanopine dehydrogenase activity after three days of exposure and strombine dehydrogenase activity starting after one overnight exposure cycle. These findings provide new insights into coral metabolic shifts in extremely low-oxygen environments and point to ADH and SDH assays as tools for quantifying the impact of hypoxia on coral health.

Proteomic responses to hypoxia at different temperatures in the Great Scallop (Pecten maximus)

Hypoxia and hyperthermia are two connected consequences of the ongoing global change that constitute major threats for coastal marine organisms. In the present study, we used a proteomic approach to characterize the changes induced by hypoxia in individuals of the great scallop, Pecten maximus, subjected to three different temperatures, i.e. 10°C, 18°C and 25°C. We did not observe any significant change induced by hypoxia in animals acclimated at 10°C. Contrastingly at 18°C and 25°C, 16 and 11 protein spots were differentially accumulated between normoxia and hypoxia, respectively. Moreover, biochemical data, i.e. octopine dehydrogenase activity and arginine assays suggests that animals grown at 25°C switched their metabolism towards anaerobic metabolism when exposed to either normoxia or hypoxia, suggesting that this temperature is out of the scallops’ optimal thermal window. In all, 11 proteins could be unambiguously identified by mass spectrometry, involved in protein modifications and signaling (e.g. CK2, TBK1), metabolism (e.g. ENO3) or cytoskeleton (GSN). The potential roles of these proteins in the thermal-dependent response of scallops to hypoxia are discussed.

Proteomic responses to hypoxia at different temperatures in the Great Scallop (Pecten maximus)

Hypoxia and hyperthermia are two connected consequences of the ongoing global change that constitute major threats for coastal marine organisms. In the present study, we used a proteomic approach to characterize the changes induced by hypoxia in individuals of the great scallop, Pecten maximus, subjected to three different temperatures, i.e. 10°C, 18°C and 25°C. We did not observe any significant change induced by hypoxia in animals acclimated at 10°C. Contrastingly at 18°C and 25°C, 16 and 11 protein spots were differentially accumulated between normoxia and hypoxia, respectively. Moreover, biochemical data, i.e. octopine dehydrogenase activity and arginine assays suggests that animals grown at 25°C switched their metabolism towards anaerobic metabolism when exposed to either normoxia or hypoxia, suggesting that this temperature is out of the scallops’ optimal thermal window. In all, 11 proteins could be unambiguously identified by mass spectrometry, involved in protein modifications and signaling (e.g. CK2, TBK1), metabolism (e.g. ENO3) or cytoskeleton (GSN). The potential roles of these proteins in the thermal-dependent response of scallops to hypoxia are discussed.

Voyage of the argonauts in the pelagic realm: physiological and behavioural ecology of the rare paper nautilus, Argonauta nouryi

Rosa, R., and Seibel, B. A. 2010. Voyage of the argonauts in the pelagic realm: physiological and behavioural ecology of the rare paper nautilus, Argonauta nouryi. – ICES Journal of Marine Science, 67: 1494–1500. The metabolic demands of a rare paper nautilus, Argonauta nouryi, in the eastern tropical Pacific (ETP) are evaluated. After adjusting for temperature and size, the rates of oxygen consumption and of aerobic and anaerobic metabolic potential (as evidenced by citrate synthase and octopine dehydrogenase activities, respectively) of A. nouryi were much higher than those in holopelagic octopods that exhibit float-and-wait predation strategies. In fact, the rates were similar to those found in small epipelagic squids and benthic octopods. The critical oxygen partial pressure was 4.9 kPa at 20°C, suggesting that the strong oxygen minimum layer found at intermediate depths in the ETP may constrain the vertical distribution of A. nouryi to the upper few metres of the water column. We also report the occurrence of a chain of shelled females at the surface, in which each animal was attached, as if on the benthos, to the next individual in the chain. Although it may constitute an effective strategy to increase the rates of mate encounter in the vast open ocean, there may be an important ecological trade-off for such behaviour, namely the increase in visibility at the surface with concomitant attraction of predators.

Aerobic and anaerobic enzymatic activity and allometric scaling of the deep benthic polychaete Hyalinoecia artifex (Polychaeta: Onuphidae)

The enzymatic activity of aerobic and anaerobic metabolic pathways in Hyalinoecia artifex, a polychaete inhabiting the deep ocean, is reported. In addition, the allometry of its anaerobic and aerobic enzymatic activity is analysed. The aerobic metabolism was measured using the electron transport system activity technique (ETS), whereas the anaerobic metabolism was estimated using the activity of lactate dehydrogenase (LDH), octopine dehydrogenase (OPDH), alanopine dehydrogenase (ALPDH), strombine dehydrogenase (STRDH), and ethanol dehydrogenase (EtOHDH). The ETS activity was about 296.18 (µLO2 h−1 g−1), which is within the range described for polychaetes and other benthic metazoans. The anaerobic enzymatic activity expressed as µmol NADH min−1 g−1 was: LDH = 0.35, OPDH = 0.11, ALPDH = 12.66, STRDH = 10.78 and SDH = 0.48. The slope of the allometric relationship between specific aerobic metabolism and body size was −0.35. In the case of the allometric scaling of the anaerobic metabolism, only LDH presented a significant relationship, with a slope of b = 0.44. This positive scaling is consistent with the pattern emerging from the scarce literature on the allometry of anaerobic metabolism in marine biota.