Predation impact of common backswimmer (Notonecta glauca L.) on juvenile narrow‐clawed crayfish (Astacus leptodactylus Esch.)

The aim of the study was to investigate the effect of the presence of common backswimmer Notonecta glauca and their potential predation, on growth, mortality, survival and cheliped loss of juvenile narrow‐clawed crayfish Astacus leptodactylus. The presence of N. glauca in tanks during the day caused a radical change in the behaviour of juvenile A. leptodactylus, which remained for more time in hiding places. At night, such differences in crayfish behaviour were not found. The negative effect of N. glauca in tanks on crayfish total body length and body weight was statistically significant (p < .05). The crayfish survival decreased with increasing the number N. glauca in tanks. The crayfish mortality in the first week was higher than in the second week. The effect of the presence of N. glauca in tanks on crayfish chelae autotomy was statistically significant (p < .05). The number of crayfish with complete sets of chelipeds decreased and the number of crayfish with loss of chelipeds increased when the number of N. glauca in tanks increased. Common backswimmers N. glauca have been effective predators not only of victims caught on the surface of water, but also of bottom‐dwelling organisms such as juvenile crayfish.     

Effect of steroidal and non-steroidal anti-inflammatory drugs on inflammatory markers in calves with experimentally-induced bronchopneumonia

The influence of treatment with steroidal (SAIDs) and non-steroidal (NSAIDs) anti-inflammatory drugs on inflammatory markers in thirty, 6-8 week old calves with induced bronchopneumonia was investigated. Animals received a single intravenous treatment with meloxicam (0.5 mg/kg body weight), flumethasone (0.05 mg/kg body weight) or sterile 0.9% NaCl (10 ml per animal). Body temperature, respiratory and heart rate, concentration of prostaglandins PGE2, PGF2alpha, thromboxane (TXB2), leukotriene (LTB4) and malonyldialdehyd (MDA) and proinflammatory cytokines i.e. tumor necrosis factor (TNFalpha) and interferon (INFalpha) were recorded in serum, bronchoalveolar lavage (BAL) and blood platelets (BP). A significant reduction of main inflammatory mediators PGE2, PGF2alpha,TXB2 and MDA after meloxicam treatment in calves with induced bronchopneumonia indicates a beneficial effect on the inflammatory processes. Contrary to effects observed by flumethasone, meloxicam induced an increase of LTB4 and INFalpha indicating that it is not immunosuppressive.     

Reciprocal hybrids of tench Tinca tinca (L.) × bream Abramis brama (L.), and tench × carp Cyprinus carpio L., and some characteristics of their early development

Reciprocal hybrids between tench Tinca tinca (L.) and carp Cyprinus carpio L., and tench and bream Abramis brama (L.) were produced artificially. The survival of all these hybrids during embryogenesis was quite high. The highest survival rate (over 60%) at the eyed stage was observed for tench and bream hybrids (both sex combinations). The hatching rates of these hybrids were also over 60%. The number of larvae with some abnormalities (i.e. deformed body) was low. In contrast, the hatching rates of tench and carp hybrids were very low (0.2%). From over 1000 fertilized eggs, only three specimens started swimming, and only one specimen survived to juvenile stage. Embryos of hybrids and their parental species differ in morphological features. These differences were also visible in the juveniles. Body parameters of juvenile hybrids produced from three species had intermediate values in comparison to parental fish.     

Determination of the optimal feeding rate and light regime conditions in juvenile burbot, Lota lota (L.), under intensive aquaculture

The aim of the study was to optimize burbot juveniles rearing in recirculating aquaculture system. In experiment 1 (17 °C, photoperiod 24L:0D), the fish (initial: body weight [W] = 15.36 ± 3.72 g, standard length [SL] = 12.48 ± 1.09 cm) were divided into four groups (I, II, III and IV). Different feeding levels were applied: 1, 2, 3 and 4 % of biomass daily (counted based on dry feed weight). The feed conversion ratio (FCR) and specific growth rate (SGR) were recorded. In experiment 2 (17 °C, feeding level of 2 % of biomass day^?1), fish (W = 5.24 ± 2.43 g and SL = 8.54 ± 1.24 cm) were divided into two groups where different light conditions were applied (I: 24 h light [1,800 lx] and II: 24 h darkness [4 lx]). In experiment 1, the highest SGR was recorded in group II (1.93 % day^?1), whereas the lowest SGR (1.27 % day^?1) and final W (P < 0.05) was in I group. The lowest (P < 0.05) FCR (0.63) was in group II. In the remaining groups, FCR was similar (0.68–0.70, P > 0.05). The feed consumption in group I reached 100 %, in group II, it was 71.3 % (P < 0.05) and it was the lowest in groups III (39.26 %) and IV (36.93 %). In experiment 2 no differences in the growth and survival rate were recorded (final SL between 14.16 and 14.19 cm, P > 0.05; W between 23.33–23.35 g; P > 0.05). The results from experiment 1 indicate that the feeding 2 % of biomass day^?1 was the most efficient. Also, it was proven, for the first time, that there was no effect of using different constant light conditions.