Goldfish

Severe hypoxia exposure and exhaustive exercise in goldfish both elicit a strong activation of substrate-level phosphorylation with the majority of the metabolic perturbations occurring in the white muscle. Approximately half of the muscle glycogen breakdown observed during severe hypoxia exposure was accounted for by ethanol production and loss to the environment, which limited the extent of muscle glycogen recovery when animals were returned to normoxic conditions. Ethanol production in goldfish is not solely a response to anoxia/hypoxia exposure however, as a transient increase in ethanol production was observed during the early stages of recovery from exhaustive exercise. These data suggest that ethanol production is a ubiquitous "anaerobic" end product, which accumulates whenever metabolic demands exceed mitochondrial oxidative potential. Exhaustive exercise and hypoxia exposure both caused a 7 to 8 μmol g − 1 wet mass increase in muscle [lactate] and the rates of recovery following these perturbations were similar. The rates of muscle PCr and pHi recovery after hypoxia exposure and exhaustive exercise were similar with levels returning to controls values within 0.5 h. Surprisingly, liver [glycogen] was not depleted during exposure to severe hypoxia, however, during recovery from both hypoxia and exercise dramatically different responses in liver [glycogen] were noted. During the early stages of recovery, liver [glycogen] transiently increased to high levels after exhaustive exercise, while during recovery from hypoxia there was a transient decrease in liver glycogen over the same time frame. Overall, this points to the liver playing a dramatically different role in facilitating recovery from exercise compared with hypoxia exposure.

During a 60 d feeding trial, goldfish (Carassius auratus) measuring 1.66 ± 0.02 g by weight and 4.2 ± 0.02 mm by length were fed diets containing 23.34%, 26.21%, 29.30%, 32.24% and 42.53% crude protein in Feeds I through V respectively. The four formulateddiets (Feeds I, II, IV and V) contained groundnut oil-cake, wheat bran, soybean meal, fish meal, cod liver oil, vegetable oil and vitamin-mineral mixture with tapioca as binder and a commercially-available diet (Feed III) procured from the market. All the feeds were dispensed twice daily at 4% body weight. Results revealed that the growth (in terms of net weight gain and specific growth rate) and dietary utilisation (in terms of feed conversion ratio, protein retention efficiency and energy retention efficiency) were observed to be significantly greater (p 6 0.05) in Feed V which contained 42.53% protein followed by Feeds IV, I, II and III, and 7.58%, 6.11%, 6.63%, 7.86% and 7.91% lipid in Feeds I through V, describing clearly the role of a combination of protein and lipid in the diet for growth and feed utilisation. Lowest growth and dietary utilisation was observed in Feed III (the commercial diet).

Stable isotope ratios of nitrogen (d 15 N) and carbon (d 13 C), complemented by stomach content data, were used to assess the food web structure and trophic transfer of mercury (Hg) in four commercial fish species of Lake Ziway, Ethiopia: Nile tilapia (Oreochromis niloticus), catfish (Clarias gariepinus), Tilapia zillii, and golden carp (Carassius auratus). Total mercury (THg in mg kg À 1 , ww) concentrations were low, with mean values of 0.033, 0.034, 0.025, and 0.011, in C. gariepinus, T. zillii, C. auratus, and O. niloticus, respectively. The relationships between mercury concentrations against total length (TL) and total weight (TW) were positive and significant in T. zillii, C. auratus, and C. gariepinus (P o 0.01), but not in O. niloticus, which even showed a decreasing tendency with increase in TL and TW. Regression of log THg vs. d 15 N among all fish species showed a significant correlation, indicating that mercury is biomagnifying along the food web of Lake Ziway. Isotope ratios indicated that C. gariepinus occupied the highest trophic level of the food web of Lake Ziway; but contained similar THg concentrations as T. zillii, which is located at a lower trophic level, probably due to a faster growth rate of C. gariepinus, and thus an example of biodilution.

A simple and novel HPLC–MS method for the simultaneous quantification of testosterone, 11-ketotestosterone, and 11β-hydroxyandrostenedione in fish serum was developed and validated. Separation was achieved on a C-18 column using a water–acetonitrile mobile-phase with a cycle time of 12 min. Ion detection was performed using ESI positive SIM at [M+H] (m/z 303, 303, 289). The linear ranges (0.2–50 ng/ml), limits of detection (0.1–0.2 ng/ml) and quantification (0.2–0.5 ng/ml) were established. The method was validated by measuring the three androgens in goldfish sera, displaying comparable values to those reported by other analytical techniques (RIA, EIA).

This study aimed to elucidate the physiological effects of high environmental ammonia (HEA) following periods of feeding (2% body weight) and starvation (unfed for 7 days prior to sampling) in gold fish (Carassius auratus). Both groups of fish were exposed to HEA (1 mg/L; Flemish water quality guideline) for 0 h (control), 3 h, 12 h, 1 day, 4 days, 10 days, 21 days and 28 days. Measurements of weight gain (%), oxygen consumption (MO2), ammonia excretion rate, ammonia quotient (AQ), critical swimming speeds (Ucrit), plasma and muscle ammonia accumulation, plasma lactate, liver and muscle glycogen, lipid and protein content were done at various time intervals during the experimental periods. Overall, ammonia excretion rates, plasma ammonia accumulation and AQ were significantly affected by food regime in ammonia free water. HEA, the additional challenge in the present study, significantly altered all the studied parameters among fed and starved groups in days-dependent manner. Results...

The present study aimed to determine whether gill macro- and microstructure show compensatory responses in three freshwater fish differing in their sensitivity to high environmental ammonia (HEA). The highly ammonia-sensitive salmonid Oncorhynchus mykiss (rainbow trout), the less ammonia-sensitive cyprinid Cyprinus carpio (common carp) and the highly ammonia-resistant cyprinid Carassius auratus (goldfish) were used as test species and were exposed for 0 h (control), 3h, 12h, 24h, 48 h, 84 h and 180 h to 1mM ammonia (as NH4HCO3; pH 7.9). In cyprinids, dramatic alterations were initiated quickly evident by thickening of filaments and lamellae, retraction of lamellae, enlargement of interlamellar cell mass (ILCM), and increase in the water-blood diffusion distance; while in trout, these modifications were absent or developed very slowly. These reorganizations may attempt to reduce the surface area presumably protecting against the water borne ammonia; and were more pronounced in goldfi...

Background Serotonin (5-HT) plays a critical role in several gastrointestinal functions in vertebrates. In teleosts lacking enterochromaffin cells, intestinal 5-HT originates from serotonergic enteric neurons. In the present study, the foregut of a stomachless teleost, the goldfish (Carassius auratus), was used to evaluate the in vitro effect of 5-HT on fish intestinal motility. We also studied the role of melatonin (MEL), an indoleamine sharing the biosynthetic pathway with 5-HT, as regulator of serotonergic activity. Methods An organ bath system, with longitudinal strips from the goldfish intestinal bulb attached to an isometric transducer was used to record foregut smooth muscle contractions. Key Results Concentration-dependent curves of the contractile response exerted by 5-HT and its agonists, 5-methoxytryptamine (5-MT) and 5-carboxamidotryptamine (5-CT), suggest a receptor-mediated action, supported by the blockade by a general 5-HT antagonist, methysergide. The 5-HT-induced contraction was abolished in the presence of atropine, revealing the involvement of cholinergic transmission in gut actions of 5-HT. Furthermore, MEL inhibited the contractile effect of 5-HT and its agonists by up to 50%, which was counteracted by MEL antagonists. Conclusions & Inferences We can provisionally propose that at least two different 5-HT receptor subtypes are involved in fish intestinal motility, a 5-HT 4 -like (5-MTpreferring) and a 5-HT 7 -like (5-CT-and fluphenazinesensitive) receptor. In summary, our results indicate that 5-HT regulates the contractile activity of goldfish foregut through specific receptors located in cholinergic neurons, and that MEL can modulate these serotonergic actions through high-affinity membrane receptors.

Fish need to balance their energy use between digestion and other activities, and different metabolic compromises can be pursued. We examined the effects of fasting (7 days) on metabolic strategies in goldfish and common carp at different swimming levels. Fasting had no significant effect on swimming performance (U crit ) of either species. Feeding and swimming profoundly elevated total ammonia (T amm ) excretion in both species. In fed goldfish, this resulted in increased ammonia quotients (AQ), and additionally plasma and tissue ammonia levels increased with swimming reflecting the importance of protein contribution for aerobic metabolism. In carp, AQ did not change since oxygen consumption (MO 2 ) and T amm excretion followed the same trend. Plasma ammonia did not increase with swimming suggesting a balance between production and excretion rate except for fasted carp at U crit . While both species relied on anaerobic metabolism during exhaustive swimming, carp also showed increased lactate levels during routine swimming. Fasting almost completely depleted glycogen stores in carp, but not in goldfish. Both species used liver protein for basal metabolism during fasting and muscle lipid during swimming. In goldfish, feeding metabolism was sacrificed to support swimming metabolism with similar MO 2 and U crit between fasted and fed fish, whereas in common carp feeding increased MO 2 at U crit to sustain feeding and swimming independently.

The aim of the present study was to investigate how photocycle and feeding-time cues regulate the daily expression of Per1a, Per2a, Per3, and Cry3 in the goldfish hindgut. For this purpose, we studied the daily rhythmicity of these genes in fish maintained under different lighting conditions and under different feeding regimes (scheduled or not). We also studied whether the timing of just one meal is able to reset the hindgut molecular clock. In a first experiment, randomly fed fish were divided into four groups and kept under different light conditions for 30 d: 12 h light and 12 h dark (12L:12D), an inverted photoperiod (12D:12L), constant darkness (24D), and constant light (24L). In a second study, fish maintained under 24L were divided into four groups fed at different time points for 35 d: (1) fish scheduled-fed once a day (at 10:00 h); (2) fish fed with a 12-h shifted schedule (at 22:00 h), (3) fish fed at 10:00 h throughout the experiment, except the last day when fed at 22:00 h; and (4) a randomly fed group of fish. Fish were sacrificed every 6 h throughout a 24-h cycle. In both experiments, gPer1a, gPer2a, gPer3, and gCry3 transcripts were quantified using Real Time-qPCR in the hindgut. Results show the clock genes gPer1a, gPer2a, and gCry3 are synchronized by both zeitgebers, the photocycle and feeding regime, in goldfish hindgut. Moreover, such clock genes anticipate light-on and food delivery, when these cues appear in a cyclic manner. In the absence of both zeitgebers, gCry3 and gPer2a rhythmicity disappeared. In contrast, the gPer1 rhythm was maintained under 24L and random feeding conditions, but not always, suggesting that food when randomly supplied is able to reset the clock depending on other factors, such as the energetic and metabolic conditions of the fish. The expression of gPer2a was not activated during the light phase of the cycle, suggesting the hindgut of goldfish is a non-direct photosensitive organ. In contrast to the other three genes, gPer3 expression in the goldfish hindgut seemed to be dependent on the timing of the last food delivery, even in the presence of a photocycle. This gene was the only one that maintained daily rhythms under both constant lighting conditions (24D and 24L), although with lower amplitude than when a photocycle was present. This indicates that, although the acrophase (peak time) of the gPer3 expression rhythm seems to be driven by feeding time, there is an interaction of both zeitgebers, food and light, to regulate its expression. In conclusion, present data indicate: (1) the hindgut of goldfish can be synchronized in vivo by both the photocycle and feeding time;