RESUMEN

Immune defence in creel-caught and trawled Nephrops norvegicus was investigated to assess a possible relationship between phenoloxidase (PO) activation and the total haemocyte count (THC). Capture, capture method and emersion evoked physiological and immunological responses that may have implications for the ability of N. norvegicus to survive the effects of such stressors. Haemolymph THC was always negatively related to PO activity in the trawled samples, suggesting a decreased level of the plasma serine proteinase inhibitors which reportedly regulate the ProPO system (Le Moullac et al. 1998; Fish shellfish Immunol 8:621-629). In contrast, creel-caught samples showed increased levels of both PO and THC (cf. control N. norvegicus), after a 12 h emersion period. Trawling and emersion evoked progressive and significant increases (p < 0.05) in the mean levels of haemolymph L-lactate, glucose and total ammonia. The evidence of overt activity and measured haemolymph parameters suggest that creel fishing yields N. norvegicus that are more likely to survive post-harvest treatments than those that are trawled.

Asunto(s)

RESUMEN

The effects of prolonged emersion (24, 48 and 72 h) and subsequent re-immersion on Nephrops norvegicus (L.) held at 5 degrees C were assessed using an index of physical quality criteria and a suite of haemolymph constituent assays. Collectively, these showed classical hypoxia-induced changes over 48 h of emersion, but, subsequently, between 48 and 72 h emersion, physical activity, haemolymph pH and circulating levels of urate, free amino acids and major ions all returned to normal (control) levels, and L-lactate levels had started to decrease towards control levels. These patterns of changes differed from that of the haemolymph total ammonia levels which continued to increase linearly throughout emersion. N. norvegicus appeared to partially compensate for the post- 48 h emersion increased levels by increasing the production, and hence relative proportions, of other less toxic nitrogenous metabolites. The data replicated that of preliminary trials. Working on the presumption that such events could occur only in the presence of oxygen, possible sources of such oxygen under prolonged hypoxia are discussed. The low holding temperature appears to be the key to prolonged survival of N. norvegicus, and the switch from anaerobic to aerobic respiration itself appears to be a function of a preceding, prolonged period of hypoxia. The ecological and commercial implications for a burrow-dwelling, benthic animal that may experience episodic periods of hypoxia and which forms a highly important proportion of the value of total UK commercial landings are discussed.

Asunto(s)

RESUMEN

The effect of ambient salinity changes (0.9, 6 and 12 psu) on the levels of dissolved ammonia (DA), ninhydrin positive substances (NPS), trimethylamine (TMA) and trimethylamine oxide (TMAO) in the blood and tissue of medium-acclimated Sander lucioperca L. (also Stizostedion lucioperca) were investigated. In freshwater, blood and tissue total free amino acid levels (measured as NPS) were 3.62 mM and 60.61 mM, respectively. The NPS content increased significantly (P<0.05) in the tissue and blood on acclimation to 6 and 12 psu salinities. The mass-specific tissue TMAO concentration of pikeperch acclimated to normal freshwater was 0.413+/-0.084 micromol TMAO g(-1). Results reveal that TMAO levels are positively influenced by the external salinity medium where significant differences in mean levels occurred between the groups (P<0.05). The calculated p[NH(3)] and [NH(4)(+)] gradients reveal that the [NH(3)] gradient was consistently low (cf. the [NH(4)(+)] gradient). The gradient of p[NH(3)] decreased with the medium increased salinities. The results suggest that freshwater pikeperch may be able to resist salinity changes by manipulation of nitrogen metabolism. Free amino acids and TMAO are involved in mediating response to salinity exposure in freshwater pikeperch.

Asunto(s)

RESUMEN

A direct spectrophotometric flow injection method for the simultaneous determination of nitrite and nitrate has been developed. The method is based on the oxidation of a phosphomolybdenum blue complex by the addition of nitrite and the decrease in absorbance of the blue complex is monitored at 820 nm. The injected sample is split into two segments. One of the streams was directly reacted with the above reagent and detected as nitrite. The other stream was passed through a copperised cadmium reductor column where reduction of nitrate to nitrite occurs, and the sample was then mixed with the reagent and passed through the cell of the spectrophotometer to be detected as nitrite plus nitrate. The conditions for the flow injection manifold parameters were optimised by experimental design and the concentration of nitrite and nitrate was determined in the linear range from 0.05 to 1.15 mug ml(-1) nitrite and 0.06 to 1.6 mug ml(-1) nitrate with a detection limit of 0.01 mug ml(-1) for nitrite and 0.025 mug ml(-1) for nitrate. The method is suitable for the simultaneous determination of nitrite and nitrate in fish and water samples with a sampling rate of 25+/-2 sample per hour.

Asunto(s)

Asunto(s)

Asunto(s)