Biochemical parameters of silver catfish (Rhamdia quelen) after transport with eugenol or essential oil of Lippia alba added to the water

The transport of live fish is a routine practice in aquaculture and constitutes a considerable source of stress to the animals. The addition of anesthetic to the water used for fish transport can prevent or mitigate the deleterious effects of transport stress. This study investigated the effects of the addition of eugenol (EUG) (1.5 or 3.0 mu L L-1) and essential oil of Lippia alba (EOL) (10 or 20 mu L L-1) on metabolic parameters (glycogen, lactate and total protein levels) in liver and muscle, acetylcholinesterase activity (AChE) in muscle and brain, and the levels of protein carbonyl (PC), thiobarbituric acid reactive substances (TBARS) and nonprotein thiol groups (NPSH) and activity of glutathione-S-transferase in the liver of silver catfish (Rhamdia quelen; Quoy and Gaimard, 1824) transported for four hours in plastic bags (loading density of 169.2 g L-1). The addition of various concentrations of EUG (1.5 or 3.0 mu L L-1) and EOL (10 or 20 mu L L-1) to the transport water is advisable for the transportation of silver catfish, since both concentrations of these substances increased the levels of NPSH antioxidant and decreased the TBARS levels in the liver. In addition, the lower liver levels of glycogen and lactate in these groups and lower AChE activity in the brain (EOL 10 or 20 mu L L-1) compared to the control group indicate that the energetic metabolism and neurotransmission were lower after administration of anesthetics, contributing to the maintenance of homeostasis and sedation status.Fundacao de Amparo a Pesquisa do Estado do Rio Grande do Sul (FAPERGS/PRONEX) [10/0016-8]; Conselho Nacional de Pesquisa e Desenvolvimento Cientifico (CNPq) [470964/2009-0]; Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); CNPqinfo:eu-repo/semantics/publishedVersio

In vitro effect of vitellogenin on steroid production by ovarian follicles of greenback flounder Rhombosolea taprina

Ovarian follicles from vitellogenic greenback flounder (Rhombosolea tapirina) were incubated in L15 medium alone, or containing human chorionic gonadotropin (hCG), dibutyryl cyclic AMP (dbcAMP) or the steroid precursors testosterone (T), 17-hydroxyprogesterone (17P) and androstenedione (A) in the presence of vitellogenin (Vtg) at 0.1–5.0 mg mL− 1. Medium concentrations of 17β−estradiol (E2) and T were measured by radioimmunoassay. HCG generally stimulated follicular E2 but not T production, whereas 17P, A and T stimulated production of E2, T, and E2 respectively. Treatment of follicles with dbcAMP inhibited follicular E2 production, but increased follicular T production at high doses. The effect of low concentrations of Vtg on follicular steroid production was variable; however, higher doses of Vtg significantly suppressed basal, hCG-, dbcAMP- and steroid precursor-stimulated follicular E2 and T production. The results of this study show that high concentrations of Vtg may suppress follicular steroid production by interfering in the steroidogenic pathway. This suggests that Vtg may regulate its own production by limiting the ovarian production of E2

The effect of stress and exercise on post-mortem biochemistry of Atlantic salmon and rainbow trout

Freshwater Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss responded similarly to increase in water flow (exercise), reduction in holding tank water level (stress), or 30 min chasing with water level reduction (stress and exercise). Stress generally resulted in elevated plasma cortisol, above the control. Fish responded to stress and exercise combined, with elevated lactate and [H+] which was sometimes associated with elevated plasma cortisol. These changes were combined with a depletion of the muscle adenylate pool. Post-mortem, thisresulted in an increase in the rate of onset of rigor, and a higher and sometimes sustained muscle proton load. Both species produced predominantly inosine as opposed tohypoxanthine, for up to 72 h of ice storage. This study shows that the physiological disruption in Atlantic salmon and rainbow trout caused by simulated harvest conditions of stress and exercise, results in mostly transient changes in post-mortem muscle biochemistry. These changes lead to an earlier onset and resolution of rigor, and lower post-mortem muscle pH in comparison to the control

Effects of elevated water temperature and food availability on the reproductive performance of a coral reef fish

Climate change is predicted to increase ocean temperatures and alter plankton communities that are food for many marine fishes. To examine the effects of increased sea surface temperature and fluctuating food levels on reef-fish reproduction, breeding pairs of the coral reef damselfish Acanthochromis polyacanthus were maintained for a full summer breeding season in an orthogonal experiment comprising 3 temperature and 2 food levels. Water temperatures were the current-day average summer temperature for the collection location (28.5°C) and temperatures predicted to become close to the average for this region over the next 50 to 100 yr (30.0 and 31.5°C). Pairs were fed either a high or low quantity diet based on average and minimum feeding rates in the wild. Both water temperature and food supply affected reproductive output. Fewer pairs bred at elevated water temperatures and no pairs reproduced at either of the higher temperatures on the lower quantity diet. Furthermore, eggs produced were smaller at 30.0 and 31.5°C compared to those at 28.5°C. Histological analysis of the gonads and steroid hormone measurement did not reveal any apparent differences in patterns of oogenesis among treatments. However, spermatogenesis was reduced at high temperatures despite some increases in plasma androgen levels. Reduced breeding rate at warmer temperatures combined with reduced sperm production indicates the potential for significant declines in A. polyacanthus populations as the ocean warms

Reproductive periodicity and steroid hormone profiles in the sex-changing coral-reef fish, Plectropomus leopardus

The reproductive biology of coral trout, Plectropomus leopardus, from the Great Barrier Reef (Australia) was investigated by correlating gonadal condition with plasma levels of gonadal steroids. Female fish were found to be regressed from mid-summer to early spring, after which rapid and cyclical increases in gonado-somatic index (IG), maximum oocyte diameter (MOD) and plasma concentrations of estradiol-17β and testosterone were detected. Male fish, in contrast, commenced recrudescence slightly earlier in winter and responded with less dramatic increases in both IG and plasma concentrations of testosterone and 11-ketotestosterone. The mode of oocyte development was multiple group-synchronous, and cyclical fluctuations in reproductive parameters (IG, MOD and gonadal steroid concentrations) were synchronized with new-moon lunar phases. It is likely, therefore, that individual P. leopardus have the capacity to spawn on multiple occasions, with lunar periodicity. However, evidence suggests that early bouts of reproduction may be more important in terms of reproductive investment than subsequent bouts later in the same season. It is concluded that patterns of gametogenesis and steroidogenesis in P. leopardus are similar to the patterns displayed by other tropical groupers, suggesting that management regimes and propagation protocols developed for these fishes may also be appropriate for use with P. leopardus

Quantitative extraction of nucleotides from frozen muscle samples of Atlantic salmon ( Salmo salar ) and rainbow trout ( Oncorhynchus mykiss ) : Effects of time taken to sample and extraction method

Muscle excised from the dorsal flank of Atlantic salmon and rainbow trout at death and up to 120 min postmortem (P.M.) was frozen in liquid N2 and stored at -8OC. Following acid extraction, on ice (method I), or dry ice (method 2) samples were anaijzed for cyclic nucleotides to determine the effect of time to sample, and extraction method. There was no pattern of change in nucleotide profile in either species up to 10 min P.M. At 120 min P.M., Atlantic salmon muscle extracted by method 2 had a higher IMP concentration than at any other time but there was nodifference in adenylates. Ignoring time taken to sample, method 2 resulted in higher adenylate and lower IMP concentration than method I . These results indicate that method 2 is most effective in obtaining realistic nucleotideconcentrations from fish muscle because it maintains the tissue temperature below the critical freeze zone, (-0.8 to -5C) prior to enzyme inactivation

Steroid hormone levels and bi-directional sex change in Gobiodon histrio

Sex change in the coral-dwelling goby Gobiodon histrio was induced by placing two adult fish of the same sex on a coral colony. The sex change of individual fish was confirmed using histology, and whole-body concentrations of the gonadal steroids testosterone (T), 11-ketotestosterone (11-KT), and 17β-oestradiol (E2) were examined. The results show that T, 11-KT and E2 occurred in both female and male G. histrio. E2 concentration in females was twice that in males, while concentrations of T did not differ between the sexes. Contrary to predictions, concentrations of T and E2 did not differ between fish that changed sex and those that did not. Most samples had 11-KT concentrations below minimum levels of detection ( i.e. <0·15 ng ml−1) and were therefore not analysed statistically. The results suggest that: (i) specific activation or de-activation of the T–E2 (aromatase) pathway is a probable candidate for mediating serial adult sex change in G. histrio, and (ii) low levels of 11-KT may be important in allowing serial adult sex change in G. histrio

Differential effects of temperature and maturity stage on hepatic estrogen receptor characteristics of Atlantic salmon

In order to determine if elevated temperature during vitellogenesis had a detrimental effect on hepatic estrogen receptors of Atlantic salmon (Salmo salar), 3H-estradiol saturation binding analysis, using one- and two-site binding models, was carried out on extracts of hepatic cytosols from fish held at 14, 18 or 22 °C over the austral period of peak vitellogenesis (February to April). With one-site binding analysis, no temperature related difference in either receptor affinity (Kd) or number (Bmax) was found at each sampling point, but there was an apparent decrease in both affinity and number at each temperature over the period of the study. However, some analyses, notably at 22 °C during February, were best described using a two-site binding model. At this temperature and time, there was a clear separation of binding affinity into high and low components (Kd=0.67±S.E. 0.05 and 20±S.E. 5.6 nM, respectively) (n=4), which suggests that February was a critical time of temperature related hepatic sensitivity to estrogen. These results support those of other studies where we found that February was also a sensitive time with respect to temperature impairment of in vitro follicular estrogen synthesis, and the greatest period of in vivo temperature sensitivity

The relationship between acute stress, food intake, endocrine status and life history stage in juvenile farmed Atlantic salmon, Salmo salar

Different life history stages of juvenile Atlantic salmon around the period of smoltification were subjected to short term stress (confinement) over two sampling years using separate cohorts of hatchery-reared fish. In the first year, confinement stress suppressed subsequent feeding in smolts and post-smolts, but not parr, in association with elevated plasma cortisol levels. Post-smolts showed much lower levels of food intake than either parr or smolts. Plasma ghrelin levels were unaffected by stress in any group. In the second study year, pre-smolts had very low food intake and this was further suppressed following stress. Higher food intake levels in smolts were strongly inhibited post-stress. Both pre-smolts, and smolts showed elevated levels of plasma cortisol and glucose, and suppressed plasma ghrelin levels. Across both study years, stress that was accompanied by elevated plasma cortisol levels resulted in suppression of feeding, whereas a predicted association of suppressed plasma ghrelin levels with reduced food intake, was present only in the second year. The results of the present study indicate that elevated plasma cortisol is a consistent endocrine correlate of stress-suppression of feeding. It is also apparent that the peri-smolt period is associated with markedly reduced feeding in this stock of Atlantic salmon