The mechanism of crustacean salinity tolerance: Cell volume regulation by K+ and glycine effluxes

The regulation of muscle fiber K⁺ and free amino acid (FAA) concentrations during hypoosmotic stress was investigated in the moderately euryhaline crab Cancer irroratus. After 6 h of exposure to 60% ASW, muscle fiber K⁺ concentration declined from 185 mM to 140 mM. Following this, the blood glycine levels began to increase, indicating an FAA efflux from the cells. These data indicate that both muscle fiber K⁺ and FAA contribute to cell volume regulation in C. irroratus. The early release of K⁺ limits the initial rate of cell hydration. The subsequent efflux of glycine accounts for the volume regulation response of the muscle fibers. The cell volume regulatory system of C. irroratus is a coordinated use of both inorganic ions and FAA.     

The metabolic demands of swimming behavior influence the evolution of skeletal muscle fiber design in the brachyuran crab family Portunidae

We investigated the influence of intracellular diffusion on muscle fiber design in several swimming and non-swimming brachyuran crabs. Species with sustained swimming behavior had aerobic dark fibers subdivided into small metabolic functional units, creating short diffusion distances necessary to support the high rates of aerobic ATP turnover associated with endurance activity. This dark fiber design was observed in all swimming species including Ovalipes ocellatus, which has apparently evolved swimming behavior independently of other Portunidae. In addition, we observed fiber and subdivision size-dependent differences in organelle distribution. Mitochondria, which rely on oxygen to function, were uniformly distributed in small fibers/subdivisions, but were clustered at the fiber periphery in larger fibers. The inverse pattern was observed for nuclei, which are not oxygen dependent, but rely on the transport of slow diffusing macromolecules. Phylogenetically independent contrast analysis revealed that these relationships were largely independent of phylogeny. Our results demonstrate cellular responses to diffusion that were necessary for the evolution of swimming and that are likely to be broadly applicable.     

Reproductive behaviour and larval development of Tanais cavolinii (Crustacea: Tanaidacea)

Mature female stages of Tanais cavolinii Milne Edwards are described according to degree of oostegite development. Sexual dimorphism of the chelipeds of copulatory males is explained functionally. An aberrant marsupium consisting of two closed ovisacs with a small slit for sperm transfer protects the brood from sudden unpredictable changes in salinity. Behavioural traits, courtship, copulation, and parental care are described and compared to those of Heterotanais oerstedi Kröyer. The different habitats selected by the two species are reflected by several adaptations in their morphology and behaviour as tube dwellers. A phenomenon unique among invertebrates is that the female T. cavolinii supplies additional yolk to the larvae just before their release. The production and timing of this food supply is described and its adaptive significance is discussed.     

The feeding mechanisms in plankton eaters

The feeding mechanisms of 15 whitefish Coregonus lavaretus (Lin.) from the Gulf of Bothnia near Holmsund were studied. The fishes were very susceptible to infection. Different preparation and anaesthesia methods were tested. Careful dissections revealed a vestigial epibranchial organ extending from the dorsal part of the fifth gill slit. It is suggested that this little sac receives and accumulates plankton organisms which may then be carried to the oesophagus via a special pharynx groove. In this way the whitefish could effectively use small plankton as a complementary food source to larger food particles.     

Assessment of non-invasive techniques for monitoring mercury concentrations in species of Amazon turtles

This study determined the concentrations of mercury (Hg) in four tissues of six species of turtles from the Rio Negro in the Amazon Basin. For two species, blood and carapace tissues were correlated with concentrations in internal tissues to establish whether blood or carapace could serve as a non-lethal indicator of internal metal exposure or body burden. The four tissues’ Hg levels were also correlated to turtle size and gender. The liver in five species of turtles had the highest concentration, followed by carapace, muscle, and blood. The exception was Chelus fimbriatus, which had a higher metal concentration in the muscle than carapace. Regarding the correlation between total Hg concentrations in tissues of the two species, no significant correlation was noted for Podocnemis erythrocephala. However, for Podocnemis sextuberculata significant correlation was found between muscle?×?liver, muscle?×?blood, and liver?×?blood. For P. erythrocephala, there was a correlation between Hg concentration in carapace and turtle size. For P. sextuberculata, there was no marked correlation between Hg concentration and size, but concentration in muscle was significantly influenced by gender. The patterns of Hg accumulation in tissues of the five species followed those described for freshwater species and some species of sea turtles. The difference in C. fimbriatus may be a result of a different pattern of non-living keratin layers on the carapace tissue. The use of carapace to infer internal concentrations of Hg is common in freshwater and sea turtles, but in this study it was found that only blood might be a reliable indicator of Hg concentrations in liver and muscle tissues for P. sextuberculata. Thus blood may be used as a non-invasive method to study concentrations of Hg in liver and muscle of P. sextuberculata.     

Functional morphology of the larval tentacles of Phragmatopoma californica (Polychaeta: Sabellariidae): composite larval and adult organs of multifunctional significance

Larvae of the sabellariid polychaete Phragmatopoma californica (Fewkes), which were collected in San Diego, California and were competent to metamorphose after 18 to 30 d of development were observed in vivo by videoequipped light microscopy, and the fine structure of the larval tentacles was examined by transmission and scanning electron microscopy. Each tentacle has tufts of at least two types of immotile cilia arranged in dorsolateral and ventrolateral rows, and a ventral groove covered by two types of motile cilia that beat independently of each other. The epidermis is regionalized into glandular, sensory, locomotory, and support cell types and contains four longitudinal bundles of basiepithelial nerve fibers. A layer of connective tissue separates the epidermis and the nerve tracts from obliquely striated muscles that occur within the peritoneum that lines the central coelomic cavities. The peritoneum forms an intact coelomic epithelium that overlies and interdigitates with the muscle cells, with no intervening basal lamina. The muscle cells are considered to be intraperitoneal because they are located above the basal lamina and they lack intercellular junctions with the peritoneal cells. Specialized peritoneal cells form a striated myoepithelial blood vessel that partitions the coelom into medial and lateral cavities. No neuromuscular junctions were found, but both muscular and ciliary movement seem to be under neuronal control. The basiepithelial nerve terminals appear to synapse into the connective tissue layer toward the intraperitoneal muscle. Several similarities in tissue organization are noted between the larval tentacles of P. californica and the tube feet of echinoderms. Observations on the ontogeny, morphology, and behavior of the tentacles suggest that they are multifunctional organs involved in feeding, construction of the juvenile sand tube, locomotion, attachment, and sensory perception during larval and adult lives.     

Biochemical adaptations of the mudskipper Boleophthalmus boddaerti to a lack of oxygen

Specimens of the mudskipper Boleophthalmus boddaerti, collected along the estuarine canal at Pasir Ris, Singapore between April 1987 and December 1989, were examined in the laboratory. After being exposed to environmental hypoxia for 6 h, no accumulation of lactate, alanine or succinate was observed in the muscle tissue of B. boddaerti. In addition, the blood lactate content and muscle creatine phosphate (CrP), adenosine triphosphate (ATP) and glycogen contents were not significantly different from those of the control. During normoxic recovery, oxygen debt repayment was only a small fraction of the oxygen deficit incurred during the 6 h of hypoxic exposure. Therefore, it would appear that B. boddaerti coped with environmental hypoxia by undergoing metabolic rate reduction. After anoxic exposure, the CrP, ATP and adenosine diphosphate (ADP) contents in the muscle tissue of B. boddaerti were significantly lower than the corresponding control values. Lactate accumulated in the blood and muscle tissue of the anoxic fish though the muscle energy charge and glycogen content remained constant. Hence, B. boddaerti was able to cope with such a period of anoxia without increasing its glycolytic rate. Succinate, which was not detected in the muscle tissue of the control and hypoxia-exposed fish, accumulated in significant quantities in the muscle tissue of B. boddaerti exposed to environmental anoxia and functional hypoxia. In the case of functional hypoxia, there was a significant decrease in the muscle glycogen content, and the muscle lactate content increased 17.3-fold, indicating that glycolysis was activated to provide the source of energy during muscular exercise.     

Neutral lipid compositions of antarctic fish tissues may reflect use of fatty acyl substrates by catabolic systems

Antarctic fishes contain large quantities of lipid in adipose tissue, blood and oxidative muscle. In this study, the fatty acyl compositions of free fatty acids (FFA) and triacylglycerol (TAG) in serum, adipose tissue and oxidative muscle were determined in two species of Antarctic fishes, Trematomus newnesi Boulenger, 1902, and Notothenia gibberifrons Lönnberg, 1905, collected off the Antarctic Peninsula in February and March 1987. Total lipid contents of serum and oxidative muscle in each species also were measured. T. newnesi, a mesopelagic species, has significantly more lipid in the serum than N. gibberifrons, a demersal species (17.6±2.4 and 10.4±1.0 mg lipid g^-1 serum, respectively). The oxidative muscle of T. newnesi also contains more lipid than does that of N. gibberifrons (12.5 and 9.3% by dry weight, respectively). Fatty acids comprising greater than 5% of one or more of the lipid pools assayed in both species include 14:0, 16:0, 16:1, 16:2, 18:0, 18:1, 20:5 and 22:6. The percentages of 16:1 were lower (p<0.05) in oxidative muscle FFA than in all other assayed lipid pools in both species, suggesting a catabolic preference for some monoenes in oxidative muscle of these fishes. The percentage of 14:0 was two-to three-fold higher in adipose tissue TAG than in all other lipid pools in both species. Differences in fatty acid compositions between lipid pools indicate than proteins involved in the mobilization, transport or catabolism of fatty acids exhibit differential recognition of fatty acids in T. newnesi and N. gibberifrons.     

Comparative biochemical composition of ploidy groups of the lion-paw scallop (<Emphasis Type="Italic">Nodipecten subnodosus</Emphasis> Sowerby) supports the physiological hypothesis for the lack of advantage in triploid mollusc’s growth in food-rich environments

Induction of triploidy in aquatic organisms has increased worldwide in the last two decades, mostly because triploids have better growth than diploids. According to a physiological hypothesis, partial or total sterility of triploids allows the accumulation of reserves in muscle and other tissues instead of being transferred to the gonad. The present study analyzes lipid, protein, carbohydrate, and fatty acid levels in muscle and gonads of Nodipecten subnodosus triploids and diploids over 18 months from June 2001 to December 2002. An important increase in gonadosomatic index of diploids scallops was observed from May to June 2002 reaching the highest values in August. Such increase was not observed in triploid scallops. Changes in biochemical composition in female gonad were in general related to the accumulation of reserves during gonad development of diploid scallops. This accumulation was lower for triploid scallops, in accordance to their sterility, especially for carbohydrates and acylglycerides. Adductor muscle index as well as protein and carbohydrate levels in muscle increased in both ploidy groups during the reproductive period indicating no mobilization of reserves to sustain gonad development in both ploidy groups. These results partially support the physiological hypothesis on the advantage of triploids: in a rich food locality no mobilization of reserves is needed to sustain gametogenesis. This, together with a possible lower efficiency of energy assimilation at high food concentration for triploids, may be the reason for an apparent lack of superiority of N. subnodosus triploids in terms of adductor muscle growth. Only the levels of particular highly unsaturated fatty acids levels (namely 20:4n-6 and 20:5n-3) in muscle of diploid and triploid decreased during the reproductive period, indicating a possible transfer of selected fatty acids to gonads, even in triploids. The muscle of triploids has a slightly but significantly higher proportion of 22:6n-3 compared to diploids, which can have implications for the nutritional and commercial value of triploid adductor muscle.     

Effects of the toxic dinoflagellate <Emphasis Type="Italic">Gymnodinium catenatum</Emphasis> on uptake and fate of paralytic shellfish poisons in the Pacific giant lions-paw scallop <Emphasis Type="Italic">Nodipecten subnodosus</Emphasis>

Juvenile Pacific giant lions-paw scallops Nodipecten subnodosus were fed the toxic dinoflagellate Gymnodinium catenatum, a producer of paralytic shellfish poison (PSP), supplied with Isochrysis galbana (a nontoxic microalgae). Short-term (<24 h) experiments were performed to determine clearance and ingestion rates of G. catenatum. Kinetics of PSP was examined in longer-term experiments (>2 days). At high food concentrations, juvenile scallops showed production of pseudofeces, partial shell valve closure, and reduction in feeding. According to HPLC analysis, the only toxins present in the dinoflagellate G. catenatum and in the scallops were the gonyautoxins (GTXs), except in the labial palps and digestive gland, where trace amounts of saxitoxin (STX) were present in scallops. These tissues could play an important role in toxin biotransformation. The ranking of toxin concentration in tissues was: digestive gland > labial palps > intestine > gills > mantle > adductor muscle, where the total contribution of viscera was more than 80% of the total toxin body burden. Juvenile scallops exhibited no apparent detrimental physiological responses during the long-term feeding experiment. The dinoflagellate may contribute nutrients to the scallop, in addition to the microalgae I. galbana. The dinoflagellate may enhance cell uptake and byssus production. Once PSP accumulated during the first 12 days, it was slowly eliminated. The limited capacity for accumulating toxins in the adductor muscle favors domestic marketing of scallops.     

Metals concentration and bioaccumulation in the marine-coastal trophic web from Buenos Aires province southern coast,Argentina

Metals accumulated in the tissues of organisms inhabiting marine ecosystems generally reflect their bioavailable levels within that environment. The aim of this work was to study the presence and concentration of metals (Cd, Cr, Cu, Fe, Ni, Pb and Zn) and its bioaccumulation in liver-ink sac (n?=?12) and muscle (n?=?12) tissues of loliginid squids, Loligo sanpaulensis, in liver (n?=?15) and muscle (n?=?15) tissues of white croakers, Micropogonias furnieri, and in muscle (n?=?12) tissues of franciscana dolphins, Pontoporia blainvillei, as representatives of different trophic levels of an estuarial ecosystem from the southern coast of Buenos Aires. Except for Pb, all metals were detectable in the hepatic tissues. Bioaccumulation was observed for Fe, Cr and Ni in muscle of squids. Zn levels in muscle samples increased with the trophic level of the species analysed. Necochea-Quequén presents relatively high levels of Ni and Cr in the tissue samples of squids and fishes given other locations of southern hemisphere, indicating a possible anthropic enrichment. These outcomes provide the necessary basis for the environmental monitoring of an area with relevance for fishing and high anthropic activity.     

Concentrations of Cd,Ni, Pb,and Cr in the two edible fish species Liza klunzingeri and Sillago sihama collected from Hara biosphere in Iran

The concentrations of four metals (Cd, Ni, Pb, and Cr) were determined in the muscles, gills, and livers of two edible fish species (Liza klunzingeri and Sillago sihama) caught from the Hara biosphere of Southern Iran. In both fish species, metal concentrations and bioaccumulation factors were in the sequence liver?>?gill?>?muscle. Bioaccumulation factors were found to be highest in S. sihama. The metal concentrations were descending in the order of Ni?>?Cr?>?Pb?>?Cd, except for muscle samples from S. sihama showing an inversion of Pb and Cr. There is a significant negative correlation between the concentrations of the metals in each tissue with length, weight, and age, except for muscle in L. klunzingeri. Some metal levels in the muscle exceeded the limits recommended by FAO, WHO, and FEPA.     

New insights into temperature-induced white muscle growth plasticity during Dicentrarchus labrax early life: a developmental and allometric study

Dicentrarchus labrax is a major finfish of interest in Mediterranean aquaculture. As the development of its hatchery production had gone with an increase of its larval rearing temperature, we studied the effect of a constant high (20°C) and two lower (13 and 15°C) temperatures on its early white muscle growth, with developmental and allometric approaches. D. labrax, sampled at hatching and at three developmental stages corresponding to main events in fish early life (first exogenous feeding, notochord flexion and completion of fin ray counts), were histologically processed in order to follow changes in the white myotomal muscle size, cellularity and localisation of proliferative nuclei. Morphometric analyses showed that, for 13, 15 and 20°C incubated/reared D. labrax, the total cross-sectional area of white muscle increased slowly in eleutheroembryos shorter than 5.2 mm, and four times faster in longer fish (free-swimming larvae). White muscle growth occurred both by hypertrophy (increase in muscle fibre size) and hyperplasia (increase in total number of muscle fibres) in all sampled fish, but both processes were higher in free-swimming larvae than in eleutheroembryos. The morphometric establishment of a higher hyperplastic growth of white muscle in free-swimming larvae was confirmed at immunological level by a high occurrence of proliferative nuclei. Early thermal environment was demonstrated to affect the growth process of white muscle on a different way in eleutheroembryos and free-swimming larvae: in the former, white muscle hypertrophy was stimulated at 20°C and hyperplasia at lower temperature, whereas in the latter, both white muscle hypertrophy and hyperplasia were more stimulated at 20°C than at lower temperatures. This was verified at once when the fish length and the white muscle total cross-sectional area were used as explicative variables.     

Distribution of mercury in some organs of the Kani Barazan wetland common coot (Fulica atra)

We document mercury distribution in the tissues (kidney, liver, breast feathers and pectoral muscle) of a waterbird, the common coot (Fulica atra) from the Kani Barazan wetlands in north-western Iran. Bird samples were collected between November 2011 and January 2012, and mercury was assayed by using a Varian 220 atomic absorption spectrophotometer. Mean levels of mercury in kidney, liver, breast feathers and pectoral muscle were 0.13, 0.22, 0.20 and 0.09 μg/g, respectively. Mercury concentrations in tissues of F. atra were in the following order: liver>feather>kidney>pectoral muscle. The mercury level was significantly (one-way ANOVA, p<0.05) different between kidneys, livers, pectoral muscles and feathers in F. atra. Although mercury concentrations were higher for all tissues in female birds compared with males, significant (p<0.05) differences were observed in muscle only.     

Lipid composition of eggs and adductor muscle in giant scallops (Placopecten magellanicus) from different habitats

Scallops (Placopecten magellanicus Gmelin) were collected during August 1989 from shallow water (10 m) and deep water (31 m) habitats at Sunnyside, Trinity Bay, Newfoundland, to compare the lipid composition of eggs and adductor muscle tissue. Less favorable food levels and lower temperature conditions associated with deeper water have previously been shown to produce slower growth and reduced fecundity in individuals from this habitat. Triacylglycerol reserves consistently accounted for 60% of the total lipids present in both groups. The total lipid content of the eggs and the composition of their triacylglycerol fatty acid pools were similar in shallow water and deep water scallops, indicating very little if any nutritional difference between the two groups. Relative to their counterparts from shallow water, individuals from deeper water contained higher proportions of docosahexaenoic acid [22:6(n-3)] in the egg phospholipids and higher levels of 24-methylenecholesterol (a phytosterol commonly found in diatoms) in the adductor muscle. Differences in fatty acid composition are interpreted as biochemical adjustments of cell membranes to increase membrane fluidity, thereby compensating for the lower temperatures prevailing at the greater depth.     

The chemical basis of food detection in the lobster Homarus gammarus

A synthetic mixture of chemicals, based on the composition of an extract of squid muscle, has been developed, which is highly attractive for the lobster Homarus gammarus (L.). None of the components of this mixture was as attractive as the complete mixture, and substitution of D-amino acids for the natural L-forms also greatly reduced the attractiveness. This would indicate that several different types of chemosensory cell must be simultaneously stimulated to initiate exploratory feeding behaviour, and that a high degree of stereospecificity is involved. The results are discussed in the context of the wide range of food materials known to attract lobsters.     

Effects of experimental feeding and starvation on the proximate composition of the European bass Dicentrarchus labrax

Juvenile bass, Dicentrarchus labrax (L.), fed ad libitum on trout pellets, the shore crab Carcinus maenas and filleted saithe, Gadus virens, did not differ significantly in proximate composition although the diets were absorbed with high efficiencies of 94 to 99% and differed greatly in composition. Compared with wild fish, the white muscle, dark muscle, liver and mesenteric fat bodies of laboratory-reared bass were lower in moisture and higher in lipid. Starvation caused a rapid initial decrease in carbohydrate and a progressive decline in lipid in all tissues, coupled with an increase in moisture and ash contents. The liver and fat body somatic indices also declined, indicating that these organs are the major lipid storage depots in bass, in contrast with the skeletal muscle which has this role in other active fishes such as salmonids and clupeids. Lipid and protein are inversely related to moisture content in whole specimens.     

Biochemical composition of cephalopods with different life strategies,with special reference to a giant squid,<Emphasis Type="Italic"> Architeuthis</Emphasis> sp.

The present study is a comprehensive comparison of the biochemical composition (protein, lipid, glycogen and cholesterol contents, and amino acid and fatty acid profiles) of 14 species of cephalopods with different life strategies (benthic, nektobenthic, benthopelagic and pelagic) in distinct habitats (neritic, demersal, oceanic and deep sea), with special emphasis placed on a male Architeuthis sp. The giant squid showed a significantly lower protein and total amino acid content in the gonad and digestive gland. The major essential amino acids were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and proline. The benthopelagic cirrate octopus Opisthoteuthis sp. showed a lower content of these nitrogen compounds in the muscle. In respect to lipid and fatty acid contents, the giant squid showed the highest values in the gonad and digestive gland and the lowest in the muscle. Most of saturated fatty acid content was presented as 16:0; monounsaturated fatty acid content, as 18:1 and 20:1; and polyunsaturated fatty acid content, as 20:4n-6, 20:5n-3 and 22:6n-3. The highest cholesterol content in the gonad was detected in Opisthoteuthis sp. and Architeuthis sp.; in the digestive gland. in Todarodes sagittatus; and in the muscle, in Sepia elegans. The highest glycogen value in the gonad was detected in Octopus vulgaris; in the digestive gland and muscle, the highest values were attained in Opisthoteuthis sp. The relationships between life strategies and biochemical composition were investigated and principal component analysis (PCA) was performed. The different cephalopod life strategies could be well separated on the basis of the first two principal components. The nektobenthic and pelagic strategies were clearly separated from the benthic, suggesting that these groups of species are characterized by lower lipid content and higher protein content in the gonad. A rather similar life-strategy distinction was obtained for the digestive gland. The benthopelagic strategy was also well separated from benthic and pelagic strategies and from Architeuthis sp. In the muscle, the results indicated lower nitrogen and carbon compound contents in Architeuthis sp. and Opisthoteuthis sp. The environmental conditions that possibly explain the Architeuthis sp. stranding, the relationships between biochemical compositions and the life strategies of the different cephalopod species studied are discussed.Communicated by S.A. Poulet, Roscoff     

The biology of colonial hydroids. II. The morphology and ultrastructure of the medusa of Eirene viridula (Thecata-Leptomedusa: Campanulinidae)

The free-swimming medusae of Eirene viridula are typical marine hydroids, with distinct subdivisions into body regions, which were studied by comparison of light and electron microscopy. Particular attention is given to the epithelio-muscular and digestive muscle cells. The epidermis — apart from a few nerve cells and cnidocytes-consists of epitheliomuscular cells. At their bases these cells form a musculature and at the apex many secretory vesicles. In the velum, large expansions of the intercellular space are found. The gastrodermis — apart from the mucous and zymogen cells in the manubrium — consists of digestive muscle cells, the structure of which corresponds in principle to that of the epitheliomuscular cells. In its apex, this type of cells contains both normal coated vesicles and discoidal coated vesicles. In the solid tentacles, the digestive muscle cells form a turgescent vesicular tissue. The central nervous system consists of the exumbrellar, subumbrellar, and gastrodermal nerve rings. They are composed of ganglion cells, their processes, and intraepithelial flagella. The static organs are purely ectodermal statocysts which have only one lithocyte and only one sensory cell.     

Seasonal variation in the properties of muscle mitochondria from the tropical scallop Euvola (Pecten) ziczac

In scallops, gametogenesis leads to considerable transfer of energetic reserves from the adductor muscle to the gonads. During an annual cycle, the scallops are exposed to changes in temperature and food availability. As these changes may affect muscle metabolic capacities, we examined whether the properties of the mitochondria in the phasic adductor muscle were modified during the annual cycle of the scallop Euvola (Pecten) ziczac (L. 1758). During our study, temperature and chlorophyll a levels generally showed an inverse relationship: high temperatures and low chlorophyll a levels occurred from mid-April to early June. Lower temperatures and higher chlorophyll a levels were found from January to late March and from mid-June to mid-September. Throughout the annual cycle, the substrate preferences and the pH sensitivity of the isolated muscle mitochondria changed little, whereas the maximal oxidative capacities and respiratory control ratios (RCR) varied considerably. Consistently, the maximal capacities for substrate oxidation were 30 to 80% lower in mitochondria isolated in May than at other times in the year. The RCR values of mitochondrial oxidation of glutamate, glutamine and succinate varied throughout the year with lower values characterizing the mitochondria from scallops harvested in May and in certain cases in August. In May, adductor muscles had lower protein levels than at other times. These data suggest that the requirements of gametogenesis, coupled with␣the high temperatures and low food availability occurring during April and May, led to a mobilization of muscle proteins which concomitantly decreased the oxidative capacity of isolated mitochondria. Received: 29 November 1996 / Accepted: 5 December 1996