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Adenylate energy charge (AEC) has been used as a practical index of the physiological status and health in several disciplines, such as ecotoxicology and aquaculture. This study standardizes several procedures for AEC determination in penaeid shrimp that are very sensitive to sampling. We concluded that shrimp can be frozen in liquid nitrogen and then stored at -76°C for up to two years for further analysis, or freshly dissected and immediately homogenized in acid. Other cooling procedures, such as immersion in cold water or placing shrimp on ice for 15 min resulted in 50% and 73% decreases in ATP levels, and 9-fold and 10-fold increases in IMP levels, respectively. Optimal values of AEC (0.9) were obtained in shrimp recently transferred from ponds to indoor conditions, but decreased to 0.77 after one month in indoor tanks when stocked at high densities; the AEC re-established to 0.85 when the shrimps were transferred to optimal conditions (lower density and dark tanks). While the levels of arginine phosphate followed the same pattern, its levels did not fully re-establish. Comparison of different devices for sample homogenization indicated that a cryogenic ball mill mixer is the more suitable procedure.

Temperature and hypoxia anomalies are observed in many coastal regions, and climate change is likely to cause a more frequent and intense occurrence of environmental extremes. Understanding their impacts on benthic populations is critical, especially on those with little or no mobility. In this contribution, the effects of hyperthermia (to 26[degrees]C) and hypoxia (to 1.0 mg [O.sub.2] [L.sup.-1]) were analyzed and compared with their combined occurrence through the evaluation of the physiological condition of juveniles of the green abalone Haliotis fulgens. Sudden, single-time exposure of 8 h and the recurrent exposure to 8-h weekly episodes for 6 wk were tested to identify changes in the physiological condition by estimating the respiration rate (RR), the biochemical contents (soluble protein [SP] and glucose [Glc]), and physicochemical variables (osmolality [Osm] and pH) in hemolymph, and energy status (adenylate energy charge [AEC]) was measured in the muscle. The strongest responses under sudden hyperthermia were an increase in RR and Osm as well as a reduction in SP, pH, and AEC, and under hypoxia and combined effects, reductions in RR, Osm, and pH were observed. Abalone's responses to the combined stressors under the recurrent regime were different, showing increases in SP and Glc contents and reductions in pH and AEC. Results suggest that under recurrent stress of hyperthermia or hypoxia alone, the juveniles of H. fulgens can adapt, whereas under recurrent events of the combined stressors, the observed response is similar to that of sudden stimuli (without evidence of adaptation). KEY WORDS: green abalone, Haliotis fulgens, temperature, hypoxia, sudden stress, recurrent stress, INTRODUCTION There is increasing awareness of the potential impacts of extreme events of high temperature (hyperthermia) and depletion of dissolved oxygen (hypoxia) in coastal marine ecosystems worldwide. Climate change projections [...]

Although laboratory experiments allow greater control of environmental conditions than field studies, they have several drawbacks. To analyze physiological responses to forcing environmental variables, experimental conditions should mimic natural conditions as closely as possible. For filter-feeding organisms in particular, diet quality and quantity is one of the environmental parameters that can differ markedly between experimental and field conditions. In the hatchery, Pacific oysters, Crassostrea gigas, commonly show good physiological performance and growth on a mixed algal diet of Tisochrysis lutea, formerly Isochrysis aff. galbana clone Tahiti (T-Iso), and Chaetoceros calcitrans, presumably as it provides a good supply of essential polyunsaturated fatty acids (PUFA) as 20:4n-6, 20:5n-3 and 22:6n-3. The present study tests whether the fluctuating biotic and abiotic conditions in the field modify the structure and function of oyster mitochondria. One group of oysters was maintained in the intertidal zone, and the other group was fed the mixed diet in a nearby experimental hatchery under salinity and temperature conditions equivalent to those in the field. After 4 weeks of conditioning, the functional capacities and membrane lipid composition of gill mitochondria were measured. For essential polyunsaturated fatty acids, only the proportion of 20:5n-3 differed between field and laboratory oysters, and confirmed the capacity of the mixed diet T-Iso + C. gracilis, to provide the essential PUFA. Nevertheless, proportions of other FA (e.g., 22:5n-6 and non-methylene-interrupted FA) differed markedly between laboratory and field-conditioned oysters. Mitochondrial oxygen uptake, cytochrome c oxidase activity, content of cardiolipin and concentration of cytochrome b were significantly lower in laboratory-conditioned than in field-conditioned oysters. These results indicate that laboratory conditioning, although allowing similar growth and gonad maturation, only partially mimics conditions that allow C. gigas to maintain mitochondrial function. Although our experimental design cannot ascertain what difference between experimental laboratory and field conditions led to changes in membrane composition and mitochondrial function, differences in nutritional quality (other than known essential PUFA) and abiotic factors (e.g., oxygen availability, emersion or daily temperature fluctuations) had a major impact on mitochondrial properties in oysters., Author(s): Tony Dudognon[sup.1] , Helga Guderley[sup.4] , Claudie Quere[sup.2] , Philippe Soudant[sup.1] , Ilie S. Racotta[sup.3] , Edouard Kraffe[sup.1] [sup.5] Author Affiliations: (1) Laboratoire des Sciences de l'Environnement Marin, Institut [...]

ABSTRACT Knowledge of the reproductive cycle of marine invertebrates of economic importance is essential for management of natural stocks and to initiate aquaculture activities. The reproductive biology of Nodipecten subnodosus [...]

Constant and oscillating egg incubation temperatures on embryonic development and early larval morphology were studied in longfin yellowtail (Seriola rivoliana Valenciennes). We investigated the effects of constant temperatures from 16 to 32°C on embryo development and larval morphology at hatch, and whether oscillating temperature during embryogenesis could lead to larval morphological variations. After hatching, larval morphology and development during yolk sac (YS) utilization were examined in larvae at constant temperatures and larvae at 25°C that had oscillating temperature during egg incubation. Hatching rates were > 75%, only decreasing to ~ 50% at 30°C. At constant temperatures, the largest larvae occurred at 22 and 24°C. The oscillating temperature did not affect the timing of embryo development but resulted in larger and smaller larvae with a smaller and bigger YS, respectively, with a similar hatching time. Therefore, a growth response occurred in embryos during a window of development before hatching, depending on the adaptive response to temperature (spawn‐specific). After hatching, most of the YS was absorbed within 24 hr in all treatments, and the growth of the larval head was a priority with an optimal development at 26°C. There was compensatory growth in smaller larvae resulting in similar sizes after YS utilization, but larvae showed variations in body structure that could be important in further aquaculture research. [ABSTRACT FROM AUTHOR]