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The article presents a study about the prevalence of epitheliocystis disease in both freshwater and marine fishes such as Nile tilapia or Oreochromis niloticus in Brazil. It examines the inhabitants of the gram-negative bacteria that cause hypertrophy of the target host cells. It also notes that the bacteria have been characterized as endosymbiontic organisms in amoeba and ciliates that reduced gill surface area for gas exchange and osmoregulation.

A feeding experiment was carried out to determine the optimal dietary lipid: carbohydrate ratio ( L: CHO, in %) on growth performance and feed efficiency in beluga, Huso huso ( Linnaeus, 1758), juveniles fed two L-carnitine supplementation levels. Triplicate groups (25 fish/tank) were fed one of eight isoproteic (41% crude protein) and isoenergetic (20 kJ kg−1 diet) diets with increasing L: CHO ratios (12 : 21, 15 : 16, 18 : 5 and 21 : 0) and one of two L-carnitine supplements (0 or 300 mg kg−1). Fish (initial body weight 480 ± 18.4 g) were housed in 24 fiberglass tanks and fed to apparent satiation for 114 days. Fish fed the 18 : 5: and 21 : 0 had higher weight gain, growth rate, feed conversion ratio and protein efficiency ratio than fish fed the other diets. Growth performance was significantly improved by supplementing 300 mg L-carnitine to diets. Liver lipid increased with increasing dietary L: CHO ratios and decreased with dietary L-carnitine level. These results indicated that juvenile beluga did not utilize dietary carbohydrate as efficiently as lipid. Moreover, diets with a dietary lipid: CHO ratio between 18 : 5 and 21 : 0 and supplemented with 300 mg L-carnitine kg−1 successfully improved growth performance and feed utilization of beluga sturgeon reared in intensive culture conditions. [ABSTRACT FROM AUTHOR]

In the present study, dry mass ( MD, μg) and routine respiration rate ( RR) (μl O2 ind−1 h−1) were measured for larval cod, Gadus morhua (L.) that were reared and tested at 5.0, 7.5, and 10.0°C. Bi-hourly measurements of RR were made on groups of larvae using a closed-circuit respirometer over a 24-h period (14L : 10D light regime) to test temperature and body size effects and whether unfed larvae exhibited diel differences in metabolism. At 10°C, the relationship between mean RR and mean MD was: ln RR = 1.16·ln MD − 6.57 (n = 31, r2 = 0.883, P < 0.001). The exponential increase in RR with temperature was described by a Q10 of 3.00. Diel differences in unfed larvae were only apparent in groups of the largest larvae. A comparison of Q10 estimates from this and other studies suggest a linear decrease in the effect of temperature on cod RR with increasing log MD for sizes encompassing larvae to large juveniles. The trend may explain, in part, observations of cod juveniles exploiting a wider range of in situ temperatures than larvae. Finally, the two most comprehensive data sets on larval cod RR compare poorly (approximately five-fold differences) and our results support the assertion that daily metabolic energy loss in many larval cod individual-based models were based upon measurements that over-estimated hourly metabolic rates by a factor of approximately four. [ABSTRACT FROM AUTHOR]

A study was undertaken to examine the effect of different amounts of dietary lysine (13 and 21 g kg-1 diet), lipid (80 and 160 g kg-1 diet) and L-carnitine (0.2 and 1.0 g kg-1 diet) on growth performance, proximate composition and amino acid metabolism of the African catfish (Clarias gariepinus ). Juvenile African catfish (23 ± 1.5 g/fish) were stocked into 70-L aquaria (16 aquaria, 28 fish/aquarium) connected to a recirculation system during a maximum period of 74 days. All groups were fed at a level of 24 g kg-0.8 day-1 in an experiment run at pair feeding. Animals receiving 1.0 g carnitine accumulated up to six times more carnitine in their tissues than animals receiving 0.2 g (P < 0.05). Acyl-carnitine and free L-carnitine levels increased in the whole body and in tissues. Dietary L-carnitine supplements increased protein-to-fat ratios in the body, but did not affect growth rate. Protein-to-fat ratios were only affected when the biosynthesis capacity of L-carnitine was restricted due to low lysine levels and when there was a shortage of dietary fat. When lysine was offered at 21 g kg-1 feed, dietary L-carnitine supplements did not affect the amino acid concentrations of body tissues. Dietary L-carnitine supplements raised the concentration of glutamic acid > aspartic acid > glycine > alanine > arginine > serine > threonine in skeletal muscle tissue (P < 0.05). Total amino acid concentration in muscle and liver tissues (dry-matter basis) increased from 506 to 564 and from 138 to 166 mg g-1 , respectively, when diets were offered with high L-carnitine, low lysine and low fat levels. These data suggest that dietary L-carnitine supplementation may increase fatty acid oxidation and possibly decrease amino acid combustion for energy. [ABSTRACT FROM AUTHOR]