Diel variability of feeding activity in haddock larvae in the East Shetland area, North Sea

Investigations of factors affecting feeding success in fish larvae require knowledge of the scales of variability of the feeding process itself and the indices used to assess this variability. In this study, we measured short-term (diel) variability in feeding rates of wild haddock larvae 4 times per day during a 10-day cruise in the northern North Sea. Feeding activity was evaluated using indices of gut fullness, prey digestive state and biochemical measurements (tryptic enzyme activity). The gut fullness and the enzyme activity indices indicated moderate-high rates of food consumption throughout the cruise. Time series analysis of the three indices showed significant diel variability in all indices and enabled identification of significant lags between food uptake and peak digestive enzyme activity. The typical pattern of food consumption and digestion was characterized by maximal ingestion of prey early in the evening (7 pm) and peak digestive enzyme activity at 1 am. The timescale over which enzyme activities reacted to prey ingestion was ca. 6 hours and is consistent with expectations from controlled laboratory experiments with other larval fish species. Significant diel variability in tryptic enzyme activity suggests that attempts to relate this measure of feeding success to other variables (e. g., food concentrations) should take care to accommodate natural cycles in feeding activity before making statistical comparisons

Quantification of trypsin with a radioimmunoassay in herring larvae (Clupea harengus) compared with a highly sensitive fluorescence technique to determine tryptic enzyme activity

Enzymatic activity and quantity of the protease trypsin were measured in individual herring larvae (Clupea harengus L.). The enzymatic activity assay was done using a fluorescence technique, and a radioimmunoassay was used for quantification of trypsin. The results are compared and the differences between the techniques discussed. Both methods gave similar results, as high or low values in trypsin quantity were reflected in high or low values of tryptic activity. Quantity and activity were linearly and positively correlated, but small differences between methods were found at the lowest detection limits. Both techniques reflect high variability between individual larvae

The effect of food availability, age or size on the RNA/DNA ratio of individually measured herring larvae: laboratory calibration

RNA/DNA ratios in individual herring (Clupea harengus) larvae (collected from Kiel Bay, Baltic Sea, in 1989) were measured and proved suitable for determining nutritional status. Significant differences between fed and starving larvae appeared after 3 to 4 d of food deprivation in larvae older than 10 d after hatching. The RNA/DNA ratio showed an increase with age or length of the larvae and was less pronounced in starving larvae compared to fed larvae. The individual variability of RNA/DNA ratios in relation to larval length of fed larvae and of larvae deprived of food for intervals of 6 to 9 d is presented. Based on the length dependency and the individual variability found within the RNA/DNA ratios, a laboratory calibration is given to determine whether a larva caught in the field has been starving or not. An example for a field application is shown

Digestive response and rates of growth in pre-leptocephalus larvae of the Japanese eel (Anguilla japonica) reared on artificial diets

As food protein digestion is instrumental for promoting growth, the main protease in young marine fish larvae, trypsin, was studied in pre-leptocephalus larvae of Anguilla japonica. Tryptic enzyme activity was monitored until day 24 and rates of growth until day 36 after hatch in larval A. japonica derived from artificially matured parent fish. Tryptic activity increased with larval age and developmental stage until day 16, after which tryptic levels stabilized. In start-feeding larvae, tryptic activities increased after ingestion of an artificial diet, but elevated tryptic activities could also be found in larvae with guts void of prey, possibly due to intestinal retention of trypsin secreted in response to ingestion of a previous meal. Gut retention time for trypsin was estimated to be at least 15 h. The gut evacuation time for the artificial diet depended on the meal size and was in the range of 1-5.5 h. Rates of larval growth in length were ca. 5% day-1 during the yolk-sac stage, declining to ca. 1% day-1 in older larvae. Vision was highly important for initiation of feeding. Results provide the first quantitative information on aspects of protein digestion in eel larvae. 2003 Elsevier Science B.V. All rights reserved

Fitness & Sports Medicine

Aim: The aim of the present study was to investigate the reactions of oxygen consumption (VO2), heart rate (HR) and lactate accumulation (La) when running on lower body positive pressure treadmills (LBPPT).Methods: 15 well-trained male athletes (VO2peak: 60.23.8ml kg-1 min-1) completed in randomized order three analogous maximal incremental treadmill tests,recording spiroergometrical data using breath-by-breath analysis. Two tests were held on a LBPPT, with 80% and 60% body weight (80% BWSet and 60% BWSet), respectively. The third test was completed on a conventional treadmill (100% BWSet).Results: Average of all running speed stages from 10 to 18 kmh-1, VO2 decreased significantly from 48.18.4 via 39.76.8 to 33.57.3ml kg-1 min-1 at 100%, 80% and 60% BWSet (p<0.001). HR was on average 15 bpm and 27 bpm lower at 80% and 60% BWSetcompared to 100% BWSet (p<0.001), while La decreased from 2.52.3 via 1.51.1 to 1.10.5 mmol l-1 (p<0.001). Conclusion: VO2, HR and La are clearly changed by LBPPT running. Furthermore, regression analyses showed that training at a fixed VO2stimulus leads to higher lactate values on the LBPPT compared to the conventional treadmill, which may indicate a change in energy contributions.KEY WORDS: AlterG, Hypogravity, LBPPT, Anti-Gravity, Oxygen Consumptio