The hemodynamics of the crustacean open circulatory system: Hemolymph flow in the crayfish ({\it Procambarus clarkii/}) and the lobster ({\it Homarus americanus/})
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Hemolymph
Procambarus clarkii
American lobster
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Few studies have evaluated the joint effects of elevated temperature and pCO2 on marine organisms. In this study we investigated the interactive effects of Intergovernmental Panel on Climate Change predicted temperature and pCO2 for the end of the 21st century on key aspects of larval development of the American lobster, Homarus americanus, an otherwise well-studied, iconic, and commercially prominent species in the northeastern United States and Atlantic Canada. Our experiments showed that larvae (stages I–III) and postlarvae (stage IV) reared in the high temperature treatments (19 °C) experienced significantly lower survival, developed twice as fast, and had significantly higher oxygen consumption rates, than those in ambient treatments (16 °C). Larvae from the ambient temperature/high pCO2 (750 ppm) treatment had significantly longer carapace lengths, greater dry masses in stages I–III and higher C: N ratios in stage IV than larvae from all other treatments. Stage IVs raised in the high pCO2 treatment at 19 °C had significantly higher feeding rates and swimming speeds than stage IVs from the other three treatments. Together these results suggest that projected end-century warming will have greater adverse effects than increased pCO2 on larval survival, and changing pCO2 may have a complex effect on larval metabolism and behaviour. Understanding how the most vulnerable life stages of the lobster life cycle respond to climate change is essential in connecting the northward geographic shifts projected by habitat quality models, and the underlying physiological and genetic mechanisms that drive their ecology.
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The growth energetics of postlarval lobsters (Homarus amer icanus) fed a brine shrimp diet (Artemia salina; 51% prot e in, prot e in:carb ohydrate = 5.1) were compared with the energetics of l obsters fed three arti{icial diets.The artificial diets were pel letized shrimp meal diets, varying in both protein (16.65-23.30%)and carbohydrate content (22.85-31.27%)and the protein:carbohydrate ratio (0.5-1.0).The best growth was measured among lobsters fed the brine shrimp diet and the 23.30% protein diet, followed by the two lowe r protein diets.
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Columbia university
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The maximal activities of enzymes in energy pathways were measured in the ventricle, hepatopancreas, and white muscle of lobster (Homarus americanus; abdominal flexor) and giant scallop (Placopecten magellanicus; phasic adductor). Both animals show an energy metabolism based upon the utilization of carbohydrate. Carnitine palmitoyltransferase activity was not detected, and this was interpreted as an incapacity for mitochondrial β-oxidation of fatty acids; the absence of 3-hydroxybutyrate dehydrogenase and D-3-hydroxybutyrate indicated that ketone bodies were not a significant energy source. The levels of hexokinase, phosphofructokinase I, citrate synthase, and cytochrome c oxidase in the myocardia of both animals suggest a dependence on the aerobic processing of both blood-borne and glycogen-derived glucose. The significance of the enzyme activity data in the hepatopancreas of both animals was not immediately apparent. The abdominal flexor muscle of the lobster and the phasic adductor of the scallop showed enzyme profiles that suggest a reliance on glycolysis to fuel rapid bursts of activity. In the lobster flexor the presence of hexokinase and phosphofructokinase I along with low levels of citrate synthase and cytochrome c oxidase indicated that this tissue can utilize blood-borne and glycogenic glucose anaerobically. The absence of hexokinase, the low levels of citrate synthase and cytochrome c oxidase, and the presence of phosphofructokinase I in the scallop adductor suggested a reliance upon glycogen-fueled glycolysis to power burst activity. 3-Hydroxyacyl-CoA dehydrogenase was found in all tissues except the lobster flexor, which was curious in light of the undetectable activity of carnitine palmitoyltransferase.
Hepatopancreas
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