Flounder Gill Research Articles

Correction of salinity with flavin-containing monooxygenase activity but not cytochrome P450 activity in the euryhaline fish ( Platichthys flesus)

To test the association between flavin-containing monooxygenases (FMOs) and osmoregulation, saltwater-adapted euryhaline flounder ( Platichthys flesus) were statically exposed to 34 (ambient), 25, and 15 parts per thousand (%.) salinity for 1 or 2 weeks. FMO activity (thiourea S-oxidase) was assayed in gill and liver microsomes in P. flesus. Branchial FMO activity was reduced dramatically (98%) in fish exposed to a salinity of 15%. as compared with control, while hepatic FMO activity was reduced by 60%. Reduction of FMO activity in response to reduced salinity (15%.) appeared to occur within 1 week or less in both liver and gill of the flounder. Although hepatic FMO activity continued to fall and was not detected after 2 weeks at 15%., branchial FMO activity was still present. A dose-response relationship in FMO reduction was present in liver, but there was no difference observed between 25 and 15%. salinity in FMO activity of flounder gill. Serum osmolality and hepatic cytochrome P450 content were unchanged by salinity. In an attempt to determine whether trimethylamine (TMA) plays a role in piscine FMO, the effect of TMA on hepatic and branchial FMO activity was examined. Intraperitoneal injections of TMA failed to induce activity. Thus, an association between osmoregulatory function and FMO expression was observed in a species of euryhaline fish, indicating that alterations by salinity may affect xenobiotic biotransformation in euryhaline animals.

A method for measuring oxygen consumption in isolated perfused gills

A method is described for measuring respiration in isolated perfused flounder gills experiencing pressures and flows similar to those seen in vivo. Mean oxygen consumption of 13 preparations bathed and perfused in identical saline was 5·00 ± 0·75 (s.e.) μ mol h−1 g wet−1, whilst that of five preparations perfused with saline but bathed in sea water (32 mg l−1) was 12·06±2·39 (s.e.) μmol h−1 g wet−1. The oxygen consumption of the seawater bathed gills was significantly higher (P<0·05) than that in saline bathed gills. These results provide direct evidence both of the high metabolic activity of the gill under normal perfusion conditions and of the increased energy expenditure of the giil in hyperosmotic, compared to isosmotic, environments.

Effect of angiotensin II on transepithelial potential in the isolated perfused flounder (Platichthys flesus) gill

Angiotensin II (Asp1, Val5) perfused through isolated flounder gills inhibited the transepithelial potential by up to 25 per cent at a concentration of 10−9M. There was no effect on gill haemodynamics and the subsequent response to 10−5 M adrenaline was normal.

Effect of angiotensin II on transepithelial potential in the isolated perfused flounder (Platichthys flesus) gill

Angiotensin II (Asp1, Val5) perfused through isolated flounder gills inhibited the transepithelial potential by up to 25 per cent at a concentration of 10−9M. There was no effect on gill haemodynamics and the subsequent response to 10−5 M adrenaline was normal.

Morphological effects of mercury exposure on windowpane flounder gills as observed by scanning electron microscopy

Windowpane flounder, Scophthalmus aquosus Mitchill, were exposed for 60 days to 5 or 10 μg 1−1 mercury and gill samples were examined by scanning electron microscopy. The response of the gill epithelium was different at the two levels of mercury exposure. The number of chloride cell apical pits and gill filaments bearing ‘cratered’ epithelial cells increased at the 5‐μg 1−1 level and decreased at the higher exposure level.Focal swellings demonstrated a dose‐dependent relationship, their numbers being greatest at the higher exposure level. Marked fragmentation of pavement cell microridge patterns and swelling of the respiratory epithelial cells was evident at the 10‐μg 1−1 exposure level.

Mode of adrenergic and peptidergic inhibition of ion transport in flounder gill.

The mechanisms of inhibition of branchial ion transport by epinephrine and somatostatin were investigated in the isolated perfused gill preparation of seawater-adapted flounder Platichthys flesus. The electrogenic transepithelial potential recorded in gills perfused and bathed with identical salines was stimulated by glucagon, forskolin, or a cyclic adenosine 5' monophosphate (AMP) derivative, each administered at a concentration identified in preliminary experiments as being submaximally effective. The subsequent abilities of epinephrine and somatostatin to inhibit the stimulated potential were found to be dependent on the site of action of the stimulatory agent with respect to the formation of cyclic AMP. Thus the maximal adrenergic or peptidergic inhibition of the potential stimulated by exogenous cyclic AMP was significantly reduced compared with the maximal inhibition of the potential stimulated by either forskolin or glucagon. The data indicate dual modes of action by which epinephrine and somatostatin achieve maximal inhibition of branchial ion transport; a cyclic AMP-independent mechanism that is effective in the presence of cyclic AMP and an additional mechanism to inhibit cyclic AMP synthesis.

Hemodynamics and potentials in isolated flounder gills: effects of catecholamines.

Branchial hemodynamics and transepithelial potentials were investigated in an isolated perfused gill preparation from the flounder (Platichthys flesus L.). An analysis of the pressure-flow profiles suggests that the gill is compliant but that the physical relationships of pressure and flow are complex. Epinephrine has a bimodal effect with an initial vasoconstriction followed by a vasodilation, the latter response being much smaller than that usually seen in teleosts. Pharmacological analysis shows 1) an alpha-mediated vasoconstriction of the arterial and venous pathway, associated with a redistribution of flow away from the venous pathway, and 2) a small beta-mediated vasodilation of the arterial pathway only. An electrical potential (inside positive) was measured across the isolated gill, bathed and perfused with an identical saline. This potential was recorded, despite the venous system being open to the external bath, and was independent of both arterial and venous flows. Epinephrine caused a significant decline in this potential, which could be resolved into a large inhibitory alpha-mediated response and a small beta-mediated stimulation.

Gill ventilation and O2 extraction during graded hypoxia in two ecologically distinct species of flatfish, the flounder (Platichthys flesus) and the plaice (Pleuronectes platessa)

Gill ventilation, breathing frequency, breath volume, oxygen extraction from the ventilatory water current and oxygen uptake through the gills were measured in flounder, Platichthys flesus, and plaice, Pleuronectes platessa, at water O2 tensions ranging from 35 to 155 mm Hg at 10° C. Ventilation volumes were similar in the two species at high water O2 tension. Exposure to hypoxic water elicited a larger increase in ventilation in the flounder. The per cent extraction of O2 from water decreased slightly in both species as water O2 tension was lowered. At comparable levels of ventilation O2 extraction was higher in flounder. At the higher levels of water O2 tension, O2 uptake across the gills of flounder was stable, the critical O2 tension being between 60 and 100 mm Hg. The plaice behaved as an oxygen conformer over the entire range of O2 tensions investigated. The superior ability of the flounder in maintaining OZ uptake across the gills during a reduction in water O2 tension may in part explain why the species, unlike plaice, inhabits very shallow waters with large fluctuations in dissolved oxygen.

The effects of copper on ionic regulation by the gills of the seawater-adapted flounder (Platichthys flesus L.)

Potentials measured in isolated, perfused gills fromPlatichthys suggest that the electrogenic ion-pump(s) contribute significantly to the potential measured in seawater. Copper added to the perfusate causes a significant reduction in the potential measured in the isolated gill and it is suggested that this is due to a direct inhibition of the branchial ion pump(s). Vascular resistance was unaffected by the presence of copper. Ouabain-sensitive oxygen consumption was reduced in tissue exposed to copper whereas residual oxygen consumption was unaffected, which suggests that the in vitro action of copper is confined to the Na+, K+ ATPase dependent portion of branchial metabolism.

Gyrodactylus pleuronecti n. sp. (Monogenea) from winter flounder (Pseudopleuronectes americanus) in Newfoundland, Canada

Gyrodactylus pleuronecti n. sp. is described from the fins, body surface, and gills of winter flounder (Pseudopleuronectes americanus) held in saltwater tanks at the Marine Sciences Research Laboratory, Memorial University of Newfoundland. Gyrodactylus pleuronecti n. sp. resembles G. avalonia Hanek and Threlfall, 1969, G. errabundus Malmberg, 1970, G. grönlandicus Levinsen, 1881, G. gymneli Zhukov, 1960, G. nainum Hanek and Threlfall, 1970, G. perlucidus Bychowsky and Poljansky, 1953, and G. pharyngicus Malmberg, 1964, in having a short hamulus root, a ventral bar with prominent anterolateral projections, and a posteriorly directed ventral membrane that tapers to a rounded extremity. However, compared with the similar species, G. pleuronecti n. sp. has relatively long hamuli (55 to 59 μm) but short marginal hooklets (27 to 29 μm). It also has a very well-developed ventral bar, which includes a comparatively long posteriorly directed ventral membrane (26 to 30 μm) of unique shape. The species description of G. pleuronecti n. sp. includes the digestive and reproductive organs but these systems proved to be similar to those of many gyrodactylids.