Paul L. Zubkoff

Anaerobic metabolism of the ribbed mussel, Geukensia demissa

Abstract 1. 1. Mussels, Geukensia demissa were incubated anaerobically for up to four days and major metabolites of each mussel were then analyzed. 2. 2. Succinate, propionate and alanine were found to accumulate anaerobically. The time dependent accumulation of alanine suggests that alanine is an important end product of anaerobic metabolism of G. demissa . 3. 3. A hypothetical scheme of bivalve anaerobic metabolism is proposed in which redox balance is maintained independently in cytosol and mitochondria.

ISOZYMES OF AURELIA AURITA SCYPHISTOMAE OBTAINED FROM DIFFERENT GEOGRAPHICAL LOCATIONS

ABSTRACT . The malate dehydrogenase (MDH, EC 1.1.1.37) and tetrazolium oxidase (TO) isozyme patterns of Aurelia aurita polyps show variations which are related to the geographical location from which these organisms were obtained. In contrast, glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) from these A. aurita polyps shows a single band with identical electrophoretic mobilities.

The occurrence of the anemone Peachia parasitica as a symbiont in the scyphozoan Cyanea capillata in the lower Chesapeake Bay

Juveniles of the burrowing anemone Peachia parasitica, living on the scyphozoan Cyanea capillata, were obtained from Virginia, thus extending the southern limit for this species. Anemones were easily maintained in the laboratory; one lived for over four years. The feeding behavior is described.

The effects of mercury, copper, and zinc on calcium uptake by larvae of the clam, mulinia lateralis

A sensitive and rapid bioassay system using Ca-45 uptake by larvae of Mulinia lateralis as indicator is described. The values of Ca uptake per larva−1 versus elapsed time were linear and some of the Ca uptake rates, expressed as pg Ca larva−1 h−1, were 148.2 (no added heavy metal), 114.4 (20 µg kg−1 of added Hg), 89.7 (200 gg kg−1 of added Zn) and 20.5 (40 µg kg−1 of added Cu). Linearities were also obtained by plotting log of Ca uptake per larva−1 against heavy metal concentrations. A new terminology, xCainf50supt, was proposed which expressed the concentration of heavy metal, x, causing 50% depression of Ca uptake over the exposure time, t. For Cu, Hg, and Zn, the values of xCainf50sup72hwere 18.5, 26.5 and 176.0 µg kg−1 respectively, which were comparable to the published values of LC50. The effectiveness of Ca uptake depression on a weight basis was Cu > Hg > Zn, and the same sequence was also observed for larval mortalities.

The calcium uptake by larvae of the oyster, Crassostrea virginica, and the clam, Mulinia lateralis

Abstract 1. 1. The uptake of calcium by larvae of the oyster ( Crassostrea virginica ) and the clam ( Mulinia lateralis ) was measured using the 45 Ca isotope tracer method. 2. 2. An equation was established for the calculation of true calcium uptake and the rates expressed as ng Ca/larva/hr were 0.39 and 0.34 ± 0.16 ( n = 4) for 3- and 11-day-old oyster larvae, and 0.03 and 0.15 for 7- and 9-day-old clam larvae, respectively. 3. 3. This system is sensitive, rapid, simple and potentially useful for the measurements of calcium metabolism, shell formation, aquaculture and toxicity.

Volatile fatty acids of the ribbed mussel, Geukensia demissa

Abstract 1. 1. Volatile fatty acids were extracted and purified from the mussel, Geukensia demissa, by a simple solvent extraction method and quantified by gas liquid chromatography. 2. 2. Propionate was most abundant with about 3 μmol/g dry weight, iso-butyrate and butyrate were near 1 μmol/g dry weight; iso-valerate was present in trace amount and valerate was virtually absent. 3. 3. The anaerobic accumulation of propionate is discussed.

Krebs cycle intermediates of the oyster, Crassostrea virginica and the mussel, Geukensia demissa☆

Abstract 1. 1. Seven Krebs cycle intermediates were extracted from the American oyster, Crassostrea virginica , and the ribbed mussel, Geukensia demissa . They were purified by Celite R 545 and basic alumina column chromatography, derivatized by boron trifluoride/methanol and quantified by gas-liquid chromatography. 2. 2. On average, succinate and malate were most abundant, then citrate and α-keto-glutarate. Cisaconitate and iso-citrate were present in trace amounts. Fumarate was detected in C. virginica but not in G. demissa . 3. 3. Concentrations of Krebs cycle intermediates of C. virginica and G. demissa were comparable to those of guinea-pig and rat. 4. 4. The potential usefulness of this method in study of anaerobic metabolism, heavy metal accumulation, calcification and osmoregulation is discussed.

MALATE DEHYDROGENASE ISOZYMES OF DIFFERENT STAGES OF CHESAPEAKE BAY JELLYFISH

1. In Aurelia aurita, there is no change in the mitochondrial MDH isozyme pattern in different stages, although a relatively small change in the cytoplasmic MDH isozyme pattern can occur.2. In Chrysaora quinquecirrha, three MDH isozyme patterns are observed: a dominant cytosol pattern in the cysts, a complex pattern in the scyphistomae and strobilae, and a simpler cytosol and mitochondrial pattern in the ephyrae and medusae.3. In Cyanea capillata, two MDH isozyme patterns occur in the different stages: the planula and planulocyst pattern and the scyphistoma and medusa pattern.4. Temperature induced differences were not observed in MDH isozyme patterns of the scyphistomae of A. aurita and C. quinquecirrha when cultured under different temperatures.5. No differences in the MDH isozyme patterns of the red and white medusae of C. quinquecirrha were detected.6. Changes in G6PD enzyme electrophoretic mobility during the development of A. aurita, C. capillata and C. quinquecirrha were not observed.

Malate dehydrogenase and tetrazolium oxidase of scyphistomae of Aurelia aurita, Chrysaora quinquecirrha, and Cyanea capillata (Scyphozoa: Semaeostomeae)

KurzfassungIm Gewebe der Scyphistomae vonAurelia aurita, Chrysaora quinquecirrha undCyanea capillata wurde das Isoenzymmuster der Malatdehydrogenase (MDH) und der Tetrazoliumoxydase (TO) durch Anwendung der Polyacrylamidgel-Elektrophorese bestimmt. Entsprechend der Reihenfolge der genannten Arten betrug die Anzahl der gefundenen MDH-Isoenzymbanden 4,5 bzw. 1, während sich die der TO-Isoenzymbanden auf 2,1 bzw. 1 belief. Es wird darauf hingewiesen, daß das Isoenzymmuster für die taxonomische Zuordnung der schwer zu unterscheidenden Scyphopolypen neben anderen Merkmalen mit herangezogen werden kann.Summary1. The malate dehydrogenase (MDH) isozyme patterns of the three most common polyps of Chesapeake Bay (USA) differ in number and in electrophoretic mobilities:Aurelia aurita: 4 bands (Rm=0.29, 0.33, 0.39, 0.43);Chrysaora quinquecirrha: 5 bands (Rm=0.21, 0.22, 0.40, 0.53, 0.54);Cyanea capillata: 1 band (Rm=0.50) or sometimes a second (Rm=0.25).2. The tetrazolium oxidase (TO) isozyme patterns differ as follows:Aurelia aurita: 2 bands (Rm=0.39, 0.51);Chrysaora quinquecirrha: 1 band (Rm=0.58);Cyanea capillata: 1 band (Rm=0.39).3. Isozyme components of MDH and TO, either singly or in combination, may be used to distinguish the common Chesapeake Bay polyps of unknown origin.

Enzymes associated with carbohydrate metabolism of scyphistomae of Aurelia aurita and Chrysaora quinquecirrha (Scyphozoa: semaeostomae)

Abstract 1. 1. A functional tricarboxylic acid cycle in the scyphistomae of Aurelia aurita and Chrysaora quinquecirrha is indicated by the presence of NADP + -linked isocitrate dehydrogenase (IDH, E.C. 1.1.1.42), succinate dehydrogenase (SDH, E.C. 1.3.99.1), and malate dehydrogenase (MDH,E.C. 1.1.1.37). 2. 2. These scyphistomae are potentially capable of survival under low oxygen conditions by utilizing phosphoenol pyruvate carboxykinase (PEPCK, E.C. 4.1.1.32), MDH, and SDH in the absence of lactate dehydrogenase. 3. 3. The Michaelis constants ( K m ), energies of activation ( E a ), and temperature dependence are reported for several enzymes. 4. 4. The scyphistomae cultured at lower temperature always have a higher substrate enzyme affinity (lower K m ) and lower E a than organisms maintained at room temperature. The reduction in velocity of enzymatic reaction with decreased temperature may be partially, or, sometimes fully, offset by a decrease of K m and E a . 5. 5. The pH dependence of pyruvate kinase (PK, E.C. 2.7.1.40), PEPCK, and MDH is discussed in relation to possible pH control at the branch point of phosphoenol pyruvate.