The post‐spawning movements of migratory brown trout Salmo trutta L.

The post spawning behaviour of sea trout Salmo trutta was studied over a 2 year period in the river and estuary of the River Fowey, south‐west England. Forty‐five sea trout kelts were trapped immediately after spawning in December and intraperitoneally tagged with miniature acoustic transmitters. The subsequent emigration into coastal waters was monitored using acoustic receivers deployed throughout the river catchment. The levels of gill Na⁺K⁺ATPase activity in sea trout kelts sampled at the same time as the tagged fish were within the range of 2·5 to 4·5 μmol Pi per mg protein per h indicating that the post‐spawning fish were not physiologically adapted to salt water. The tagged kelts were resident in fresh water between 4 and 70 days before entering the estuary. Sixty two per cent of the tagged kelts subsequently migrated successfully into coastal waters, with a higher success rate for male fish (75%) than females (58%). There was a significant size related difference in the run‐timing of the kelts with the larger fish moving more quickly into coastal waters after spawning than smaller fish. Seaward migration within fresh water was predominantly nocturnal and generally occurred in conjunction with increasing river discharge and rising water temperature. Migration through the estuary continued to be predominantly nocturnal and occurred during an ebbing tide. Residency within the estuary varied amongst individuals although it was invariably short, with most fish moving out into coastal waters within one to two tidal cycles. Five tagged kelts returned from the coastal zone and re‐entered fresh water during April and June. Marine residence time varied between 89 and 145 days (mean 118 days) and the minimum estimated marine survival was c. 18%. One of these sea trout was subsequently recaptured after successfully spawning in the vicinity where it had been previously tagged demonstrating a degree of spawning site fidelity.     

Changes in branchial and intestinal osmoregulatory mechanisms and growth hormone levels during smolting in hatchery-reared and wild brown trout

Evidence of smolting was studied in Danish hatchery-reared brown trout Salmo trutta L. Twenty-four hour seawater (SW) challenge tests (28‰, 10°C) at regular intervals showed that maximal hypo-osmoregulatory ability developed within a 3–4-week period in March and April. The improved ability to regulate plasma osmolality, muscle water content and plasma total [Mg] developed asynchronously, indicating that developmental changes in the gill, the gastrointestinal system and the kidney may not necessarily concur during smolting. Gill Na⁺, K⁺-ATPase activity peaked in April at the time of optimal hypo-osmoregulatory ability. Na⁺, K⁺-ATPase a -subunit mRNA level in gills was unchanged from January until April, but decreased in May in parallel with a decrease in the activity of the enzyme. In the middle region of the intestine, Na⁺, K⁺-ATPase activity increased in February and remained high until April. In the posterior region of the intestine, the activity was stable from January until April after which it decreased. In vitro fluid transport capacitity, J_v, in the middle intestine fluctuated throughout the spring. In the posterior intestine, J_v was low until late March, when it increased fivefold until early May. Drinking rate in fish transferred to SW for 24 h surged during spring. Na⁺, K⁺-ATPase activity in the pyloric caeca was elevated from March until May, and increased in response to SW transfer in June, suggesting a hypo-osmoregulatory function of the pyloric caeca. Plasma GH levels surged in FW trout during spring, concurring with the increase in gill Na⁺, K⁺-ATPase activity and SW tolerance, but peaked in May when gill Na⁺, K⁺-ATPase activity and SW tolerance were regressing. GH levels were generally low in SW-challenged fish, and there was no consistent effect of 24-h SW exposure on GH levels. In wild anadromous trout, gill Na⁺, K⁺-ATPase activity varied seasonally as in hatchery-reared fish, but peaked at higher levels suggesting a more intense smolting in fish living in their natural environment.     

Enhancement of pH‐resistant iron‐binding activity in supernatants of rainbow trout blood leucocytes by in vitro treatment with phorbol‐12‐myristate‐13‐acetate

Leucocyte lysates from rainbow trout Oncorhynchus mykiss showed an iron‐binding activity that was retained even if the samples were exposed to an acid pH (4·5). Iron‐binding activity of leucocyte supernatants was enhanced by the presence of 1 μg ml⁻¹ phorbol‐12‐myristate‐13‐acetate in the cell medium.     

Genetic differences in physiology, growth hormone levels and migratory behaviour of Atlantic salmon smolts

Out of five strains of Atlantic salmon Salmo salar of 1+ years released upstream of a fyke net in the River Gudenaa in 1996, three, Lagan, Ätran and Corrib, migrated immediately, 50% of the recaptured fish reaching the net in 3–6 days. Burrishoole and Conon fish migrated with a 15–19 day delay. Smolt development in 1997 at the hatchery showed a spring surge in gill Na⁺, K⁺-ATPase activity in all strains which was correlated with increased seawater tolerance. Differences in the timing of gill enzyme development matched the observed migration pattern well. Lagan, Ätran and Corrib strains reached high enzyme activity earlier than the Burrishoole and Conon strains, and strains with delayed enzyme development and migration showed a delayed regression of seawater tolerance compared with the early strains. Inter-strain differences in plasma growth hormone profiles could not be related to the observed patterns of Na⁺, K⁺-ATPase and seawater tolerance development. The study gives evidence of genetic influence on the timing and intensity of smolting and subsequent migration in Atlantic salmon.     

Migration of hatchery‐reared Atlantic salmon and wild anadromous brown trout post‐smolts in a Norwegian fjord system

Hatchery‐reared Atlantic salmon Salmo salar ( n  = 25) and wild anadromous brown trout (sea trout) Salmo trutta ( n  = 15) smolts were tagged with coded acoustic transmitters and released at the mouth of the River Eira on the west coast of Norway. Data logging receivers recorded the fish during their outward migration at 9, 32, 48 and 77 km from the release site. Seventeen Atlantic salmon (68%) and eight sea trout (53%) were recorded after release. Mean migratory speeds between different receiver sites ranged from 0·49 to 1·82 body lengths (total length) per second (bl s⁻¹) for Atlantic salmon and 0·11–2·60 bl s⁻¹ for sea trout. Atlantic salmon were recorded 9, 48 and 77 km from the river mouth on average 28, 65 and 83 h after release, respectively. Sea trout were recorded 9 km from the release site 438 h after release. Only four (23%) sea trout were detected in the outer part of the fjord system, while the rest of the fish seemed to stay in the inner fjord system. The Atlantic salmon stayed for a longer time in the inner part than in the outer parts of the fjord system, but distinct from sea trout, migrated through the whole fjord system into the ocean.     

Changes in gill Na+, K+ -ATPase specific activity during seaward migration of wild juvenile chinook salmon

Migration of wild juvenile chinook salmon Oncorhynchus tshawytscha during the first 80 km of their 254 km migration through the Rogue River, Oregon, was significantly slower than that during the last 170 km. Gill Na⁺, K⁺ -ATPase specific activity did not increase significantly during the first 38 km of migration. Specific activities during the next 43 km did increase significantly. Specific activities continued to increase as the fish moved downstream, reaching a maximum within 44 km from the Pacific Ocean.     

Late migration and seawater entry is physiologically disadvantageous for American shad juveniles

Juvenile American shad Alosa sapidissima were subjected to isothermal transfers into sea water (salinity 24)‘early’(1 September; 24° C) and ‘late’(10 November; 10° C) in the autumn migratory season. Early acclimation resulted in a modest osmotic perturbation that recovered rapidly. Haematocrit declined by 14% at 24 h, recovering within 48 h. Plasma osmolality increased by 6% at 4 h, recovering within 8 h. Early acclimation caused a two‐fold increase in gill Na⁺, K⁺‐ATPase activity by 24 h and a four‐fold increase by 4 days. The number of chloride cells on the primary gill filament increased two‐fold by 4 days. Chloride cells on the secondary lamellae rapidly decreased from 22 cells mm^?1 to <2 cells mm^?1 within 4 days. Late acclimation resulted in a severe and protracted osmotic perturbation. Haematocrit levels declined by 23% at 4 days, recovering by 14 days. Plasma osmolality increased by 36% by 48 h, recovering by 4 days. Initial gill Na⁺, K⁺‐ATPase activity was two‐fold greater than in ‘early’ fish and did not change during acclimation. Initial numbers of chloride cells on the primary filament were two‐fold greater than ‘early’ fish and did not increase during acclimation. Initial number of chloride cells on the secondary lamellae was five‐fold greater than ‘early’ fish (116 v. 22 cells mm^?1) and declined to negligible numbers over 14 days. Differences between initial measures for ‘early’ and ‘late’ fish reflect previously described physiological changes associated with migration. These data indicate that late migrants face a greater physiological challenge during seawater acclimation than early migrants. Physiological performance apparently limits the observed duration of autumnal migration.     

Identification and purification of the calcium‐regulated Ca2+‐ATPase from the endoplasmic reticulum of a higher plant mechanoreceptor organ

Erythrosin b, a potent inhibitor of the Ca²⁺‐ATPases and the Ca²⁺‐release channel (BCC1) in mechanosensitive tissue of Bryonia dioica Jacq., effectively suppresses a tendril's reaction to touch, suggesting that Ca²⁺‐transporters are involved in signal transduction in this organ. The Ca²⁺‐ATPase located in the endoplasmic reticulum (ER) represents a multiregulated enzyme that is stimulated by calmodulin (CaM), KCl and lysophospholipids. Limited proteolysis of ER‐membranes by trypsin results in an irreversible activation of the Ca²⁺‐ATPase and loss of the CaM sensitivity, presumably through removal of an autoinhibitory domain where CaM binds. Mild trypsination mimics the effects of CaM on V_max and the affinity for Ca²⁺ and ATP. Irrespective of a trypsin treatment, the enzyme can be additionally stimulated by KCl and lysolipids, indicating that the sites of interaction for these effectors are not located in the domain removed by the protease. CaM‐stimulated ATPase activity was purified from microsomal and ER fractions using a combination of CaM‐affinity and anion‐exchange chromatography. The isolated polypeptide was enzymatically active, showed a calcium‐dependent mobility‐shift in SDS‐PAGE from 109 kDa in the absence of Ca²⁺ to 104 kDa in the presence of 10 m M CaCl₂ and could be radiolabeled with [³⁵S]‐CaM. The characteristics of the purified enzyme remained closely similar to those of the ER‐bound Ca²⁺‐transporting activity, including the enzymatic data, CaM stimulation, and the sensitivity towards a range of inhibitors.     

Evaluation of biochemical methods for the non‐destructive identification of sex in upstream migrating salmon and sea trout

Female‐specific markers of reproductive activity [plasma 17β‐oestradiol (E2), vitellogenin (VTG) and alkali‐labile phosphoprotein phosphorous (ALP)] were measured over 12 months in a captive population of brown trout Salmo trutta . During the early months of the reproductive season (February to May) and using the concentration of plasma E2 or plasma ALP as a marker for females the proportion of fish in which sex was misidentified was high (15–50%). The misidentification rate was considerably lower (1–8%) using plasma VTG. Preliminary evaluation of a commercial immunochromatographic VTG test system as a screen for the presence or absence of VTG in plasma from brown trout provided results that were consistent with those obtained from direct measurement of plasma VTG levels by enzyme‐linked immunosorbent assay (ELISA). These preliminary conclusions were verified by sampling upstream‐migrating anadromous brown trout, sea trout, and Atlantic salmon Salmo salar trapped over a 6 month period. Plasma E2 levels did not satisfactorily discriminate between male and female sea trout and Atlantic salmon. Plasma VTG levels in both species, however, were bimodally distributed and it was assumed that this divergence corresponded to male (plasma VTG levels <10 μg ml⁻¹) and female (plasma VTG levels >800 μg ml⁻¹) fishes. Plasma ALP provided a more accurate indication of sex in the wild Atlantic salmon and sea trout than was suggested by the pilot study on captive brown trout. The commercial immunochromatographic VTG test system provided results that were wholly consistent with the data obtained from the trapped fishes by direct measurement of plasma VTG.     

Axonal Contact Regulates Expression of α2 and β2 Isoforms of Na+,K+-ATPase in Schwann Cells: Adhesion Molecules and Nerve Regeneration

Abstract: Three isoforms of catalytic α subunits and two isoforms of β subunits of Na⁺,K⁺-ATPase were detected in rat sciatic nerves by western blotting. Unlike the enzyme in brain, sciatic nerve Na⁺,K⁺-ATPase was highly resistant to ouabain. The ouabain-resistant α1 isoform was demonstrated to be the predominant form in rat intact sciatic nerve by quantitative densitometric analysis and is mainly responsible for sciatic nerve Na⁺,K⁺-ATPase activity. After sciatic nerve injury, the α3 and β1 isoforms completely disappeared from the distal segment owing to Wallerian degeneration. In contrast, α2 and β2 isoform expression and Na⁺,K⁺-ATPase activity sensitive to pyrithiamine (a specific inhibitor of the α2 isoform) were markedly increased in Schwann cells in the distal segment of the injured sciatic nerve. These latter levels returned to baseline with nerve regeneration. Our results suggest that α3 and β1 isoforms are exclusive for the axon and α2 and β2 isoforms are exclusive for the Schwann cell, although axonal contact regulates α2 and β2 isoform expressions. Because the β2 isoform of Na⁺,K⁺-ATPase is known as an adhesion molecule on glia (AMOG), increased expression of AMOG/β2 on Schwann cells in the segment distal to sciatic nerve injury suggests that AMOG/β2 may act as an adhesion molecule in peripheral nerve regeneration.     

Changes in oxidation‐reduction state and antioxidant enzymes in the roots of jack pine seedlings during cold acclimation

The role of glutathione and the response of components of the ascorbic acid‐glutathione cycle in cold acclimation and the acquired freezing tolerance of jack pine ( Pinus banksiana Lamb.) seedlings were investigated. An increase in the reduced to oxidized glutathione mole ratio was correlated with the increase in root soluble and membrane‐bound protein thiol concentrations during cold acclimation and after a freeze and thaw event. All the enzymes involved in the ascorbic acid‐glutathione cycle were regulated by low temperatures and increased activities of ascorbic peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, and glutathione reductase were observed after the conditioning of the seedlings to low temperatures. Our results suggest that these enzymes play a protective role following the exposure of the seedlings to freezing temperatures.