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Atmospheric particulate matter (APM) emitted by iron ore processing industries has a complex composition, including diverse metallic particles and nanoparticles. Settleable APM (SePM) causes air to water cross-contamination and has recently been demonstrated to have harmful sublethal impacts on fish, eliciting stress responses, affecting the immune system, and reducing blood oxygen-carrying capacity. These findings imply potential consequences for fish aerobic performance and energy allocation, particularly in their ability to tolerate respiratory challenges such as aquatic hypoxia. To assess that potential limitation, we analyzed metabolic, cardiorespiratory, and morphological alterations after exposing tilapia, Oreochromis niloticus, to an environmentally relevant concentration of SePM (96 h) and progressive hypoxia. The contamination initiated detectable gill damage, reducing respiratory efficiency, increasing ventilatory effort, and compromising fish capacity to deal with hypoxia. Even in normoxia, the resting respiratory frequency was elevated and limited respiratory adjustments during hypoxia. SePM increased O2crit from 26 to 34% of O2 (1.84 to 2.76 mg O2·L−1). Such ventilatory inefficacy implies higher ventilatory cost with relevant alterations in energy allocation. Progression in gill damage might be problematic and cause: infection, blood loss, ion imbalance, and limited cardiorespiratory performance. The contamination did not cause immediate lethality but may threaten fish populations due to limitations in physiological performance. This was the first investigation to evaluate the physiological responses of fish to hypoxia after SePM contamination. We suggest that the present level of environmental SePM deserves attention. The present results demonstrate the need for comprehensive studies on SePM effects in aquatic fauna.

Seawater temperatures in Antarctica are low, and typically rather stable seasonally. Associated with this, many marine invertebrates have low resting metabolic rates with a limited aerobic scope, and are often stenothermal. We have therefore investigated the response of metabolic rate and protein synthesis to feeding in the large Antarctic isopod, Glyptonotus antarcticus, at two different temperatures. The resting oxygen consumption of starved Glyptonotus was low, and comparable with a previous measure for this species and other Antarctic marine invertebrates. Resting metabolic rate exhibited a Q10 of 2.18 between 0°C and +4°C. After feeding at 0°C, oxygen consumption increased by a factor of 2.5 and ammonia excretion eightfold, before returning to prefeeding levels, in a classic if somewhat prolonged SDA (specific dynamic action) response. At 4°C, the postprandial factorial increase in both oxygen uptake and ammonia excretion was reduced. Whole-body protein synthesis rates for prefeeding animals showed a similar Q10 to oxygen consumption. Rates of synthesis increased significantly after feeding, and there was an associated drop in the O:N ratio, indicating that protein formed the primary metabolic substrate during the SDA response. The contribution of the costs of protein synthesis to the overall SDA was estimated to be 68%, although this estimate is based on a previous estimate of the costs of protein synthesis in Glyptonotus which is higher than typical values for temperate-water crustaceans. The fraction of ingested energy utilised in the SDA was, however, low (2-3%). Further work is needed to determine whether these unusual features in Glyptonotus are typical of polar marine invertebrates in general.

Transgenic tilapia hybrids (Oreochromis mossambicus × O. hornorum) carrying a single copy of a homologous cDNA growth hormone exhibit higher growth rates than their wild-type conspecifics (Martinez et al. 1999). Swimming respirometry was employed to determine whether the increased growth rate was linked to elevated rates of maintenance metabolism in transgenics, and if this, in turn, influenced their scope to increase O2 uptake and perform exercise or their ability to maintain O2 uptake during progressive hypoxia. Individual transgenics or wild-types, of similar mass and length (60.0 ± 10 g and 14.7 ± 0.9 cm vs. 75.8 ± 16 g and 15.7 ± 1.0 cm, respectively, n = 6) were exposed to stepwise increments in swimming speed (U), of 0.5 body lengths s-1 (bl s-1) every 30 min, in a Brett-type swimming respirometer at 25¡C. Oxygen uptake was measured at each speed until fatigue. Extrapolation of the exponential relationship between U and O2 uptake back to a notional stationary baseline was taken as an estimate of maintenance metabolism. This was significantly higher in transgenic vs. wild-type fish (8.63 ± 0.86 vs. 5.39 ± 0.27 mmol O2 kg-1 h-1, respectively). However, maximum O2 uptake was also slightly higher in transgenics, such that aerobic scope was similar in both groups, and there was no difference in maximum sustainable U (5.2 ± 0.5 vs. 4.5 ± 0.7 bl s-1 in transgenics vs. wild-types, respectively). Following 2 h recovery from exercise, tilapia were exposed to progressive hypoxia (stepwise reductions in water O2 partial pressures (PO2) from 18.4 down to 1.3 kPa), and O2 uptake measured at each PO2. Despite higher routine rates of O2 uptake in transgenics, the critical P

Udgivelsesdato: May, 2000, European eels (Anguilla anguilla, L.) were fed on a commercial diet supplemented either with 15% by dry feed weight of menhaden oil (MO), an oil rich in highly unsaturated fatty acids of the n-3 series (n-3 HUFA), or with 15% by dry feed weight of coconut oil (CO), an oil composed primarily of saturated fatty acids (SFA). Following 90 days of feeding, the mean final masses of eels fed the two different oil supplements were similar, and higher than the mean final mass of a group fed the commercial diet alone. The diets created two distinct phenotypes of eels, distinguished by the fatty acid (FA) composition of their tissue lipids. Eels fed MO had significantly more total n-3 FA and n-3 HUFA in muscle and liver lipids than did eels fed CO, leading to higher n-3/n-6 and eicosapentaenoic acid/arachidonic acid ratios in the MO group. Measurements of O2 uptake (MO2) revealed that the MO group had a significantly lower routine metabolic rate (RMR) than the CO group. When exposed to progressive hypoxia, both groups regulated MO2 at routine normoxic levels until critical water O2 partial pressures that were statistically similar (9.62±1.08 kPa in MO versus 7.57±1.07 kPa in CO), beyond which they showed a reduction in MO2 below RMR. The MO group exhibited a significantly lower MO2 than the CO group throughout hypoxic exposure, but the percentage reductions in MO2 below their relative RMR were equal in both groups. During recovery to normoxia, both groups exhibited an increase in MO2 to rates significantly higher than their RMR. Throughout recovery, MO2 was significantly lower in the MO group compared with the CO group, but the percentage increases in MO2 relative to RMR were equal in both. During progressive hypoxia, neither group exhibited a marked ventilatory reflex response, both showed similar reductions in blood O2 partial pressure and content

Editors: Aug. 1859-July 1865, J. D. White, J. H. McQuillen, G. J. Ziegler.--Aug. 1865-Dec. 1871, J. H. McQuillen, G. J. Ziegler.--Jan. 1872-May 1891, J. W. White.--July 1891-Apr. 1930, E. C. Kirk (with L. P. Anthony, Dec. 1917-Apr. 1930).--May 1930-Dec. 1936, L. P. Anthony., Vols. 1-13 are called "new series.", Merged in Jan. 1937 with: Journal of the American Dental Association, ISSN 1048-6364, to form: Journal of the American Dental Association and dental cosmos, ISSN 0375-8451., The Dental cosmos; a monthly record of dental science. [Vol. 64] : Vol 64 : Issue 5, Page(s) 527-529, (dlps) volume: 0527912.0064.001, (dlps) article: 0527912.0064.001:309, http://quod.lib.umich.edu/t/text/accesspolicy.html