Air Temperature and Emersion Time Can Affect the Survival Rate and Ammonium Loading of Swimming Crab Portunus trituberculatus Exposed to Air

Ammonium overloading is a common response of aquatic organisms to air exposure during transport. This study elucidated the relationship between ammonium overloading and mortality of crab Portunus trituberculatus. Additionally, we also explored the effects of emersion time and air temperature on ammonium loading and concomitant physiological change. To test the air temperature effect, the crab was exposed to 16, 23 and 30℃ in air for 3 h, respectively, and then recovered in seawater at 23℃ for 12 h. To test the emersion time effect, crab was exposed to 23℃ in air for 0.5 and 3 h, respectively, and then recovered in seawater at 23℃ for 12 h. In the control group, crab was always immersed at 23℃. At each time interval(0.5, 1.5 and 3 h during air exposure and 0.5, 2, 4 and 12 h during recovery), ammonium excretion rate, level of total ammonium, total free amino acids and urea concentration in hemolymph and the hepatopancreas enzyme activity involved in detoxifying ammonium were analysed. Results showed that crab mortality was positively related with emersion time and temperature while ammonium loading was lower at 16 and 30℃ than at 23℃. For crab experiencing thermal inconsistence of culture media(i.e., 16 or 30℃), they were higher in ammonium excretion rate and activities of ammonium detoxification enzymes, which may be the reason that they had a lower ammonium loading. Prolonged emersion time(3.0 h vs. 0.5 h) increased the ammonium overloading and the activity of ammonium detoxification pathways in crab. Our results demonstrated that emersion-induced ammonium overloading may not be the main reason leading to P. trituberculatus death during air exposure and subsequent recovery. When the culture medium changed, thermal variation, compared with constant temperature, could reduce ammonium overloading in crab by elevating the activities of ammonium detoxification enzymes and ammonium excretion rate during recovery period.

From Enaction to Emersion:A body perception by awareness of living body

Body perception has analysed by motor activity. This is largely the result of Le Boulch’s work on psychokinetics and psychomotor education,which made new levels available for the description of body schema activity beyond that of conscious movements. Reflex movements,involuntary gestures,and emotions are all evidence of the pre-attentional activation and preparation for motor actions. Body perception is built from the interaction between the body and the world. With this in mind,we would like to draw attention to the current paradoxical gap in the literature that exists between the living and the perceived body. We then propose a means of overcoming this gap through a description of the activation of the living body and its emersion at the level of perception. Enaction,in Francisco Varela’s groundbreaking work,explains how neurodynamics bring emergences from our living body to our consciousness by awakening and activating our potential capacities. In this sense enaction is a neurodynamics,while emersion ensures the bottom-up transition of implicit information from the living body(Leib) to consciousness and to the attentive perception of the lived body(Korper).

Metabolic Plasticity of Nitrogen Assimilation by Porphyra umbilicalis(Linnaeus) Kützing

The physical stresses associated with emersion have long been considered major factors determining the vertical zona- tion of intertidal seaweeds. We examined Porphyra umbilicalis （Linnaeus） Kiitzing thalli from the vertical extremes in elevation of an intertidal population （i.e. upper and lower intertidal zones） to determine whether Porphyra thalli acclimate to different vertical elevations on the shore with different patterns of nitrate uptake and nitrate reductase （NR） and glutamine synthetase （GS） activities in response to different degrees of emersion stress. We found that the nitrate uptake and NR recovery in the emersed tissues took longer in lower intertidal sub-population than in upper intertidal sub-population; and GS activity was also significantly affected by emersion and, interestingly, such an activity was enhanced by emersion of thalli from both upper and lower intertidal zones. These results sug- gested that intta-population variability in post-emersion recovery of physiological functions such as nutrient uptake and NR activity enables local adaptation and contributes to the wide vertical distribution ofP. umbilicalis. The high GS activity during periodic emer- sion stress may be a protective mechanism enabling P umbilicalis to assimilate nitrogen quickly when it again becomes available, and may also be an evidence ofphotorespiration during emersion.