Effects of diet on responses to exhaustive exercise in Nile tilapia (Oreochromis nilotica) acclimated to three different temperatures (original) (raw)
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Prolactin plays an essential role in ion uptake as well as reduction in ion and water permeability of osmoregulatory surfaces in euryhaline fish. Kryptolebias marmoratus is a euryhaline fish with unique internal selffertilization. In order to understand the effect of different salinities and environmental endocrine-disrupting chemicals (EDCs) on the regulation of prolactin (PRL) and prolactin receptor (PRLR) genes, the full-length sequences of PRL and two PRLR genes were cloned from K. marmoratus. The expression pattern of K. marmoratus PRL (Km-PRL) and PRLR (Km-PRLR1, Km-PRLR2) mRNAs was analyzed in different developmental stages (2 dpf to 5 h post-hatching) and tissues of hermaphrodite fish. To investigate the effects of salinity changes and EDC exposure, the mRNA expression pattern of PRL, PRLR1 and PRLR2 was analyzed in exposed fish. The Km-PRL mRNA in the hermaphrodite was predominantly expressed in the brain/pituitary, the Km-PRLR1 mRNA was highly expressed in the intestine, while the Km-PRLR2 mRNA was intensively expressed in the gills. The expression of the Km-PRL mRNA generally increased from stage 1 (2 dpf) to stage 3 (12 dpf) in a developmental, stage-dependent manner. It decreased in stage 4 (12 dpf) and the hatching stage (stage 5). Km-PRLR1 and Km-PRLR2 mRNAs showed a gradual increase in expression from stage 1 (2 dpf) to stage 4 (12 dpf) and decreased by stage 5 (5 h post-hatching). Also, both mRNAs of PRLR showed a different expression pattern after exposure to different salinity concentrations (0, 33, and 50 ppt) in juvenile fish. The expression of PRL mRNA was upregulated at 0 ppt, but was downregulated at a moderately higher salinity concentration (33 to 50 ppt). The Km-PRLR1 mRNA showed upregulation at freshwater stress (0 ppt) compared to other concentrations of salinity (33 ppt to 50 ppt). The Km-PRLR2 mRNA was marginally upregulated at freshwater stress (0 ppt), but was downregulated at a higher salinity concentration (50 ppt) and showed no significant change in expression at 33 ppt salinity. Interestingly, both mRNAs showed upregulation in the brain (e.g. Km-PRL) and intestine (e.g. Km-PRLR1) after EDC exposure. These findings suggested that Km-PRL and two Km-PRLR mRNAs would be useful in analyzing the effect of different salinities as well as the modulatory effect of EDC exposure on these gene expressions in K. marmoratus.
1996
The effects of exhaustive exercise on 0, consumption (I&), waste nitrogen (ammonia and urea) excretion, and on lactate, ammonia and water content of white muscle and liver, were determined in tilapia fed a diet enriched either in long chain polyunsaturated fatty acids of the w3 series (03 LCPUFA) as menhaden oil (menhaden oil diet; MOD) or in saturated fatty acids (SFA) as coconm oil (coconut oil diet; COD), and acclimated to three different temperatures (16", 23" and 33°C). At all temperatures, exhaustive exercise elicited an increase in postexercise Go2 and ammonia excretion rates, and in white muscle lactate and ammonia levels. There were no differences between the two dietary groups in the total amount of O2 consumed and muscle lactate accumulated, but at 23°C and 33°C exhaustive exercise stimulated a significantly greater increase in ammonia excretion in COD as compared with MOD tilapia. The magnitude of the difference in postexercise ammonia excretion between COD and MOD animals increased with increases in environmental temperature, being greater at 33°C than at 23°C. The increased ammonia excretion observed in the COD group was not a result of differences in white muscle ammonia or water content following exhaustive exercise. The data indicate that diets enriched in 03 LCPUFA are beneficial in that tilapia fed these diets exhibited reduced ammonia excretion following exhaustive exercise, compared with tilapia fed diets enriched in SFA.
Using a tame animal, the impact of otter (Lutra lutra) disturbance on over-wintering carp (Cyprinus carpio) was monitored in two experiments, 133 and 140 days, respectively, over two consecutive winters (November-April). The level of stress in over-wintering carp exposed to various intensities of disturbance by otters was quantified using biological indicators of stress (cortisol, cortisone, indices of nitrogen, carbohydrate, lipid and mineral metabolism and activity of basic blood plasma enzymes) taken from blood plasma of stocked carp at the end of the winter seasons (when the photoperiod was 12 light:12 dark, respectively, 13L:10D). Moreover, condition (Fulton's coefficient of condition and fat content in muscles) and mortality rate of that carp were measured after over-wintering and also after the subsequent vegetation period. The analysis of blood and tissue samples of experimental fish showed changes in nitrogen, carbohydrate and mineral metabolism as well as levels of hormones and fat reserves. Higher response to stress in metabolism of carp with lower intensity of disturbance by otter suggests that high level of disturbance can lead to metabolic adaptation of carp to stress. The effect of stress on the mortality rate of carp during the overwintering is not clear. Nevertheless, the negative effect of stress on survival, condition and growth rate of carp in the subsequent vegetation period was not observed.
Gut blood flow in fish during exercise and severe hypercapnia
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2001
This paper reviews the effects of exercise and hypercapnia on blood flow to the splanchnic circulation. Brief struggling Ž . behaviours are known to decrease blood flow to the gut GBF . Likewise, prolonged swimming in unfed fish has been shown to reduce GBF in proportion to the increased oxygen uptake. Therefore, the normal postprandial increase in GBF theoretically should be impaired whenever fish are active. However, indirect evidence suggests that GBF is spared Ž . to some degree when fed fish swim continuously but at a cost 10᎐15% to their critical swimming speed. Severe respiratory acidosis can be created by the new intensive aquaculture settings that use oxygen injection into re-circulated water. The only study so far to examine the effects of severe hypercapnia on GBF and its regulation showed that routine Ž . GBF and ␣-adrenergic control of GBF remained normal in unfed white sturgeon Acipenser transmontanus . However, severe hypercapnia produced a hyperactive state and increased sensitivity of GBF to struggling. As a result, routine GBF was maintained for a short period of time. Thus, environmental changes such as severe hypercapnia can indirectly impact GBF through altered struggling behaviour, but the implications of the overall reduction in GBF to food assimilation have yet to be established. ᮊ A.P. Farrell .
Nutrition of Atlantic Salmon (Salmo salar): The Requirement and Metabolism of Arginine
Comparative Biochemistry and Physiology Part A: Physiology, 1997
This experiment was conducted to determine the dietary arginine requirement of medium sized Atlantic salmon (383 Ϯ 62 g) given a high energy diet (26.1 KJ/g). Zein was used as major protein source in the experimental diets supplemented with synthetic amino acids resembling the amino acid pattern of fish meal, with the exception of arginine. Arginine content was 11.3 (2.7), 16.8 (4.0), 20.2 (4.8), 26.0 (6.2), and 28.6 (6.8) g/kg dietary dry matter (% of dietary protein). Expressed in terms of digestible energy the arginine content was 0.53, 0.78, 0.94, 1.21, and 1.33 g/MJ. Protein content on dry weight was 42% in all diets. Weight gain and protein efficiency parameters were together with increasing levels of urea and ornithine in plasma and free arginine in muscle and plasma used to indicate the requirement of arginine. The growth and protein retention obtained indicated that Atlantic salmon has a requirement of arginine of 21.2-21.6 g/kg dietary dry weight (5.0-5.1% of the protein) or 1.0 g/MJ digestible energy. The metabolic parameters indicated a requirement of 20.2 g/kg dietary dry weight (4.8% of the protein) or 0.94 g/MJ. Increased dietary levels of arginine seemed to interact with the tissue free concentrations of several indispensable amino acids. comp biochem physiol 117A; 4:501-509, 1997.