P. Bronzi

Oxygen consumption and ventilatory reflex responses are influenced by dietary lipids in sturgeon

The effects of one years feeding with diets enriched either in highly unsaturated fatty acids of the w3 series (w3 HUFA) (fish oil-supplemented diet, FOD) or in saturated fatty acids (SFA) (coconut oil-supplemented diet, COD) on fatty acid composition of tissue lipids, on patterns of resting oxygen consumption and on responses to hypoxia and hypercapnia were investigated in the Adriatic sturgeon (Acipenser naccarii). FOD sturgeon had higher levels of w3 HUFA in liver and muscle lipids than COD fish, which had higher levels of SFA. A frequency distribution of instantaneous oxygen uptake rates (M]O2), as measured every 10 min for 8 h, revealed a different pattern of resting oxygen consumption between the two groups. The FOD sturgeon consumed oxygen in a narrow range of low rates, with a lower mean M]O2 than COD sturgeon, which showed a wide range of more elevated rates. FOD sturgeon had a lower opercular pressure amplitude than COD fish in normoxia. Exposure to three levels of hypoxia PO2s = 10.8±0.2; 6.6±0.2 and 4.6±0.2 kPa) or mild hypercapnia (PCO2 = 1.0±0.2 kPa) did not affect ventilation in FOD fish but elicited hyperventilation in COD animals. Mild hypoxia (PO2 = 10.8±0.2 kPa) and hypercapnia caused less reduction in blood oxygen content in FOD as compared with COD sturgeon. The effects of adding vitamin E supplements to the diets was investigated; groups fed vitamin E supplements had elevated M]O2 and hyperventilated in hypoxia. The data indicate that dietary fatty acid composition influences resting M]O2 in sturgeon and that this influences the regulation of ventilation and blood O2 levels in hypoxia and hypercapnia. The low resting M]O2 of fish fed w3 HUFA supplements (the FOD group) obviated the need for hyperventilation in hypoxia or hypercapnia, thereby making them less sensitive to these stresses than sturgeon fed SFA (COD group) or sturgeon fed either diet supplemented with vitamin E.

Effects of diet on responses to exhaustive exercise in Nile tilapia (Oreochromis nilotica) acclimated to three different temperatures

Abstract The effects of exhaustive exercise on O 2 consumption (Ṁ O 2 ), waste nitrogen (ammonia and urea) excretion, and on lactate, ammonia and water content of white muscle and liver, were determined in tilapia fed a diet enriched either in long chain polyunsaturated fatty acids of the ω3 series (ω3 LCPUFA) as menhaden oil (menhaden oil diet; MOD) or in saturated fatty acids (SFA) as coconut oil (coconut oil diet; COD), and acclimated to three different temperatures (16°, 23° and 33°C). At all temperatures, exhaustive exercise elicited an increase in postexercise Ṁ O 2 and ammonia excretion rates, and in white muscle lactate and ammonia levels. There were no differences between the two dietary groups in the total amount of O 2 consumed and muscle lactate accumulated, but at 23°C and 33°C exhaustive exercise stimulated a significantly greater increase in ammonia excretion in COD as compared with MOD tilapia. The magnitude of the difference in postexercise ammonia excretion between COD and MOD animals increased with increases in environmental temperature, being greater at 33°C than at 23°C. The increased ammonia excretion observed in the COD group was not a result of differences in white muscle ammonia or water content following exhaustive exercise. The data indicate that diets enriched in ω3 LCPUFA are beneficial in that tilapia fed these diets exhibited reduced ammonia excretion following exhaustive exercise, compared with tilapia fed diets enriched in SFA.

Effects of Plasma Total Ammonia Content and pH on Urea Excretion in Nile Tilapia

Nile tilapia (Oreochromis niloticus) were infused with ammonium salts, acid, and base to investigate the effects of changes in arterial plasma total ammonia content (Tamm) and pH (pHa) on plasma urea‐nitrogen (urea‐N) levels and urea‐N excretory fluxes (Jurea‐N). The tilapia did not possess a functional hepatic ornithine urea‐cycle (no significant carbamyl phosphate synthetase III activity). Infused substances were dissolved in a saline vehicle and injected twice (5 mL kg−1), the first infusion to “prime” the animal and promote a more marked response to the second infusion, given 2.5 h later. The results reported are those of the second infusion. Infusion of 200 mM NH4Cl increased Tamm, reduced pHa, and increased plasma urea‐N and Jurea‐N. Two hundred mM NH4HCO3 increased Tamm and arterial plasma total CO2 content ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Some aspects of osmotic and ionic regulation in Adriatic sturgeon Acipenser naccarii. II: Morpho-physiological adjustments to hyperosmotic environments

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Highlights of the 3rd International Symposium on Sturgeon: Conclusions and Recommendations

\end{document} ), reduced pHa, and increased Jurea‐N. Fifty mM HCl reduced pHa but had no effects on urea dynamics. Fifty mM NaOH increased pHa, plasma urea‐N levels, and Jurea‐N. Two hundred mM NaHCO3 increased pHa, \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Aspects of early development in the Adriatic sturgeon Acipenser naccarii

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