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.     

Occurrence of the parasite Glugea hertwigi in young‐of‐the‐year smelt in Lake Tuusulanjärvi

Young‐of‐the‐year smelt Osmerus eperlanus in Lake Tuusulanjärvi were examined for Glugea hertwigi cysts. Cysts were visible on smelt in the beginning of August and showed a peak at the end of August. Glugea hertwigi may cause mortality among the most heavily infected young‐of‐the‐year smelts.     

Otolith description and age‐and‐growth of Kurtus gulliveri from northern Australia

The sagitta of Kurtus gulliveri was ovate, moderately thick with the following attributes: lateral surface convex, mesial surface flat; dorsal margin sinuate, posterior margin rounded ventrally, ventral margin rounded and irregular; sulcus divided into ostium and cauda by constriction of dorsal and ventral margins, heterosulcoid, colliculum heteromorph; dorsal depression large and distinct, ventral groove close to margin in larger otoliths; rostrum broad and antirostrum small, separated by wide, shallow excisural notch. Otolith size was moderate, average 4·6% standard length ( L _S), typical for a perciform. Annuli on 78 whole sagittae were read, and 15% of these were transversely sectioned for verification of the annuli. Males ranged from 94 to 235 mm L _S and females from 95 to 284 mm L _S. There was little difference in size distribution of the sample between the sexes, perhaps due to a 6 month spawning season over which young were continually added to the population. Some sexual dimorphism was noted, however, as age 2 year females were significantly larger than males of the same age. The largest fish aged was a 284 mm L _S, 3 year‐old female, and the oldest age reached was 4 years by two males. It appears likely that most spawning females are ≥2 years old, but some larger 1 year old fish may attain sexual maturity.     

Inter‐individual differences in rates of routine energy loss and growth in young‐of‐the‐year juvenile Atlantic cod

Inter‐individual differences in rates of routine (non‐feeding) metabolism and growth were evaluated in young‐of‐the‐year (YOY) juvenile Atlantic cod Gadus morhua . Rates of O₂ consumption, CO₂ production and ammonia (TAN) excretion were measured in 64, 25–43 mm standard length ( L _S) YOY growing at different rates (0·27–0·47 mm day⁻¹) in a common rearing tank. Parameter rates ( y ) increased allometrically ( y = a·M^b ) with increasing body mass ( M ) with b ‐values for O₂ production, CO₂ consumption and TAN excretion equal to 0·81, 0·89 and 0·56, respectively. In some cases, residuals from these regressions were significantly negatively correlated to fish growth rate. In no cases did residuals of parameter rates increase with increasing growth rate. These data suggest that, during unfed periods, relatively fast‐growing fish were more metabolically efficient than slower‐growing fish from the same cohort. The fish condition factor, derived from     , also significantly decreased with increasing growth rate. Results indicated differences in both the rates of routine energy loss and the patterns of growth allocation among YOY Atlantic cod. Since these physiological attributes were positively correlated with growth rate, they may be indicative of 'survivors' in field populations.     

A new method to evaluate egg‐to‐fry survival in salmonids, trials with Atlantic salmon

A new method to estimate the survival of salmonids from egg fertilization to fry emergence is described. Fine mesh screen cylindrical capsules, 12 cm³ in volume, filled with batches of 10 eggs of Atlantic salmon Salmo salar were implanted in the substratum using small removable guiding tubes inserted with a metal spike. The method was compared with two other commonly used techniques, capping redds with fry‐traps and fine mesh screen incubation‐emergence boxes buried into the gravel. Egg‐to‐fry survival was recorded for the three methods run in parallel in artificial redds created on three sites of the Nivelle River watershed (south‐west of France), two in the stream and one in an experimental spawning channel. In the channel, survival to the eyed stage and to hatching in capsules and incubation‐emergence boxes was also compared. The implant of capsules proved easier and faster to use than other methods, the structure of the surrounding substratum was less disturbed and the capsules were less vulnerable to spates. This technique provided survival values largely free of the bias induced by other methods and intermediate between that of incubators and of traps.     

The use of pulse‐echo acoustic microscopy to non‐invasively determine the sex of living larval sea lampreys

A rapid, accurate and non‐invasive method to determine the sex of larval sea lampreys Petromyzon marinus , using wide‐field pulse‐scanning acoustic microscopy, is described. Cross‐sectional pulse‐echo scans were made with a high‐resolution acoustic microscope in 48 larvae (110–130 mm total length, L _T), and the acoustic images generated showed such internal body structures as the gonad, intestine, kidneys, cardinal veins, notochord and musculature. Females were identified by the presence of a relatively large (1–1·5 mm diameter) ovary, which was considerably less reflective to the 15 to 25 MHz acoustic signals than the surrounding kidney tissue. Males were recognized by the lack of the large non‐reflective ovary and, in some cases, the appearance of a small (0·2–0·3 mm) testis with slightly stronger reflective properties than the kidney. Identification of sex was confirmed by optical microscopy following dissection, and in a blind test on an additional 10 specimens (121–168 mm L _T), the acoustic method reliably identified sex in 100% of the larvae. These results indicate that acoustic microscopy can determine the sex of live sea lamprey larvae in c . 30 s per animal, a process which until now required dissection or invasive surgery.     

Endo‐1,4‐β‐glucanase gene expression and cell wall hydrolase activities during abscission in Valencia orange

The physiological and molecular events of ethylene‐induced abscission in mature fruit calyx, laminar and floral abscission zones of cv. Valencia orange were examined. Continuous exposure of fruit explants to 5 µl 1⁻¹ ethylene for 2 to 40 h resulted in marked increases in endo‐1,4‐β‐glucanase (cellulase) and polygalacturonase (PG) activities in calyx abscission zones. Two abscission‐related cellulases and one PG were found. The major peak of cellulase activity corresponded to a pI of 8.0 and molecular weight of 51 kDa, whereas the minor cellulase peak had a pI of 5.5. The abscission polygalacturonase had a pI of 5.5. Calyx abscission zone RNA was amplified with degenerate primers based on sequence of the purified Valencia orange calyx abscission cellulase, and cloned. The two partial cellulase cDNA clones were 59% identical at the nucleotide level. Genomic Southern analysis suggested that Valencia orange contained two groups of cellulase genes. A full‐length cDNA clone from each group was isolated from a cDNA library prepared from ethylene‐induced calyx abscission zone mRNA. Both genes were expressed in ethylene‐induced calyx, laminar and floral abscission zones, but were not expressed in non‐induced abscission zones or mature leaves treated with or without ethylene, young bark or young fruit of Valencia.     

Patterns of density‐dependent growth in juvenile stream‐dwelling salmonids

Literature data for 19 populations from 16 different studies of six species of stream‐dwelling salmonids were analysed to test the hypothesis that density‐dependent growth is stronger at low rather than at high population density. Fifteen of 19 populations showed evidence of a significant decrease in growth rate with increasing density. In 11 of these 15 populations, the pattern of density‐dependent growth was better described by a negative power curve than by a linear regression ( i.e . Akaike Information Criterion, AIC _linear −  AIC _power > 2), whereas only one population was better described by a linear regression than by a negative power curve; three populations were adequately described by both models ( AIC  < 2). In 10 of the 11 populations that were best described by a negative power curve, most of the decrease in growth rate occurred at population densities <1 fish m⁻², when space limitation is unlikely. This analysis provides broad support for the hypothesis that density‐dependent growth in stream salmonids occurs primarily at low population densities, probably due to exploitative competition.     

Heat‐shock proteins and cross‐tolerance in plants

Environmental stresses dramatically affect plant survival and productivity. Because plants are immobile, presumably different strategies are required for protection against transient stresses. Under stress, plants synthesize specific proteins, and their accumulation has a role in protecting the tissue from possible damage. An increasing number of studies show the existence of cross‐tolerance in plants: Exposure of tissue to moderate stress conditions often induces resistance to other stresses. Many varied mechanisms explaining the phenomenon of cross‐tolerance have been proposed, and they often, but not always, suggest that specific proteins are induced by one kind of stress and are involved in the protection against other kinds. Although various cross‐protections have been demonstrated in a number of plants, a common mechanism has not been found. This review discusses heat‐shock proteins and their possible roles in protecting the plant under heat and other stresses.     

Gustatory responses to feeding‐ and non‐feeding‐stimulant chemicals, with an emphasis on amino acids, in rainbow trout

Specific receptor and fibre types of rainbow trout Oncorhynchus mykiss involved in the detection and discrimination of amino acids and a heterogeneous collection of compounds were investigated by recording the electrical activity of the maxillary branch of the facial nerve innervating taste buds inside the upper jaw. Proline (Pro), alanine (Ala), leucine (Leu), betaine (Bet) and 2‐amino‐3‐guanidinopropionic acid (Agp) were the major amino acids detected by the gustatory system. The two experimental approaches, concentration‐response curves and cross‐adaptations, showed that all amino acids were detected by three independent receptor types: Pro ‐, Agp/Bet ‐ and Leu ‐receptors. Bile acids, the most potent stimulants recorded, were detected by a single receptor type independent of those for amino acids, with threshold concentrations of 10⁻¹² M. Strychnine, quinine and tetrodotoxin may have partially shared a single receptor mechanism. The gustatory sensibility narrowly tuned towards the amino acid spectrum compared to those for a diverse array of non‐feeding stimulant chemicals, combined with feeding behaviour triggered primarily by vision and olfaction, suggest that in rainbow trout, and possibly other salmonid species, gustatory chemical cues, in addition to food finding and intake, play an important role in detecting poisonous prey and substances.     

Return migration of one‐sea‐winter Atlantic salmon in the River Tana

Fifty‐three one‐sea‐winter Atlantic salmon Salmo salar (45–63 cm L _T) were radio‐tagged in the Tana fjord, Barents Sea, in 1995. Thirty‐seven fish (70%) entered the freshwater zone of the River Tana in an average of 3 days after release in the fjord. The migration speeds in the lowest river section below the first riffle area were significantly higher than in the subsequent river section below the second riffle area. Similarly, the observed time spent in the first riffle area was significantly lower than in the next riffle area. The majority of Atlantic salmon entered the river during the hours of high tide and the subsequent ebb tide. In addition, most river entries were recorded around midnight. No effects of river flow on the river entry or migration speed were detected, but the migration speed of Atlantic salmon in both river sections examined was greater at lower temperatures. Twenty‐eight fish (72%) were recaptured in the river, 71% of them with weirs and gillnets, and 29% by rod and line. Over half of the Atlantic salmon (54%) were recaptured within 3 weeks following river entry, and within the first 100 km of the river (56%). The results are discussed in relation to earlier studies on multi‐sea‐winter Atlantic salmon in the River Tana.     

c‐erbB‐2 and p53 expression in breast cancer fine needle aspirates

The aim of this study was to co‐evaluate c‐ erbB ‐2 and p53 protein expression in breast cancer fine needle aspirates (FNA) and to compare this with histological variables and the immunohistochemical phenotype of the tumours. Furthermore, we assessed the relationship of c‐ erbB ‐2 and p53 immunocytochemical expression to tumour prognostic factors. We examined 124 breast cancer FNAs and 79 matched surgical specimens using the avidin–biotin complex (ABC) and the alkaline phosphatase immunocytochemical techniques. C‐ erbB ‐2 immunopositivity was detected in 37.9% of the FNAs, while 31.7% were positive for p53. A statistically significant correlation was observed between p53 negativity and absence of c‐ erbB ‐2 immunostaining in the FNAs ( P =0.0007). Smears from infiltrating ductal carcinomas tended to be more frequently positive for p53 (36.7%) than those from lobular carcinomas (11.7%) ( P =0.054). In matched tumour tissues, c‐ erbB ‐2 was positive in 16.7% and p53 in 19% of cases. The immunocytochemical results for both c‐ erbB ‐2 and p53 were significantly correlated with the immunohistochemical results. There was no correlation between c‐ erbB ‐2 and p53 immunostaining, in both FNAs and tissues, and patients' menopausal status, tumour size, grade and lymph node status.     

Age effects on diel activity patterns of juvenile Atlantic salmon: parr are more nocturnal than young‐of‐the‐year

In the summer Atlantic salmon Salmo salar parr were predominantly active at night, while young‐of‐the‐year were equally active during day and at night. These findings are consistent with the prediction that larger animals should be less willing to risk predation for a certain increase in size than smaller animals.     

Density‐dependent growth in hatchery‐reared brown trout released into a natural stream

Hatchery‐reared brown trout Salmo trutta stocked in a natural stream in addition to resident wild brown trout grew more slowly than those stocked with an experimentally reduced density of brown wild trout. In both cases, hatchery‐reared brown trout grew more slowly than resident wild fish in control sections. Mortality and movements did not differ among the three categories of fish. The results showed that growth of stocked hatchery‐reared brown trout parr was density‐dependent, most likely as a consequence of increased competition. Thus, supplementary release of hatchery‐reared fish did not necessarily increase biomass.     

Evidence for an intrarenal renin‐angiotensin system in the European lesser‐spotted dogfish

The existence of an intrarenal renin‐angiotensin system (RAS) in a perfused European lesser‐spotted dogfish Scyliorhinus canicula trunk preparation was examined by the inhibition of angiotensin‐converting enzyme by captopril. This resulted in a glomerular diuresis, an increase in urea and chloride clearance and excretion, and an increase in transport maxima for glucose. It is proposed that these results suggest the presence of an intrarenal RAS.     

Population structure of lake‐type and river‐type sockeye salmon in transboundary rivers of northern British Columbia

The population structure of 'lake‐type' and 'river‐type' sockeye salmon Oncorhynchus nerka , primarily in transboundary rivers in northern British Columbia, was examined with a survey of microsatellite variation. Variation at 14 microsatellite loci was surveyed from c . 3000 lake‐type and 3200 river‐type sockeye salmon from 47 populations in six river drainages in British Columbia. The mean F _ST for the 14 microsatellite loci and 47 populations was 0·068, and 0·034 over all river‐type populations. River‐type sockeye salmon were more genetically diverse than lake‐type sockeye salmon, with expected heterozygosity of river‐type sockeye salmon 0·72 and with an average 12·7 alleles observed per locus, whereas expected heterozygosity of lake‐type sockeye salmon was 0·65 with and average 10·5 alleles observed per locus. River drainage of origin was a significant unit of population structure. There was clear evidence of genetic differentiation among river‐type populations of sockeye salmon from different drainages over a broad geographic range in British Columbia.     

Female‐biased migration of stream‐dwelling Dolly Varden in the Shiisorapuchi River, Hokkaido, Japan

The first evidence for female‐biased migration in a partially migratory stream‐dwelling salmonid the Dolly Varden Salvelinus malma , a phenomenon well known in sea‐run and lake‐run populations, is presented. Dolly Varden in the Shiisorapuchi River in central Hokkaido, Japan, used both tributaries, of which there are many, and the main stem, but spawned only in tributaries. The size structures of Dolly Varden (≥age 1 + years) in tributaries were unimodal (<100 mm fork length, L _F) during non‐spawning seasons but changed to bimodal during spawning seasons (lower mode <110 mm, upper mode >120 mm L _F). Mature individuals were observed in both modal groups. From the trapping and census data, the small group appeared to be tributary resident and the large group main stem migrant. Males were common in both resident and migrant components. Most females, however, migrated to the main stem to mature, indicating female‐biased migration.     

Effects of temperature on free‐embryonic diapause in the autumn‐spawning bitterling Acheilognathus rhombeus(Teleostei: Cyprinidae)

In bitterling Acheilognathus rhombeus , developmental arrest always occurred at stage D of the free‐embryonic phase, regardless of incubation temperature. Developmental arrest was terminated only by a cold treatment at 4° C for 60–90 days, initiated 10 days post‐hatching. After the termination of developmental arrest, free‐embryos became larvae c . 6 months after hatching, regardless of the time of initiation and duration of the cold treatment. In hybridization experiments between A. rhombeus and several species of spring‐spawning bitterlings, free‐embryos became free‐swimming larvae within 60 days after hatching in all experiments. Developmental arrest was not observed in any of the hybrids, regardless of parental sex. These results suggest that free‐embryonic diapause in A. rhombeus is not induced by environmental factors, such as cold, but by genetic factors, which are recessive to those in spring‐spawning bitterlings. Free‐embryonic diapause in A. rhombeus appears to be an adaptation to winter, which might have evolved with reproduction in autumn among autumn‐spawning bitterling species. This is the only report of free‐embryonic diapause after hatching in fishes, and only the second example of diapause in fishes, along with annual killifishes (Rivulidae).     

The effects of habitat‐ and diet‐based cues on association preferences in the three‐spined stickleback (Gasterosteus aculeatus)

A number of recent papers have investigated the potential of familiarity to organize the distributions of free‐ranging animals. It is not clear, however, to which extent individual recognition or a more general recognition of a group odour is responsible for familiarity preferences. First, we tested the sensory basis of the recognition of familiars in three‐spined stickleback ( Gasterosteus aculeatus ). When allowed to choose between a familiar and an unfamiliar stimulus shoal on the basis of both visual and chemical communication, visual communication only and chemical communication only, the preference of focal fish for familiars was shown to be dependent on the presence of chemical cues. We subsequently investigated the mechanisms underlying such association preferences, specifically the effects of recent habitat and diet on preferences. Experimental fish were divided into four treatment groups consisting of two environment treatments (saline and freshwater) and two diet treatments ( Daphnia spp. and chironimid larvae). Focal fish subsequently showed significant association preferences for groups of unfamiliar fish that had undergone the same environment or diet treatment as themselves, suggesting self‐referent matching. These data indicate that individual recognition is not a pre‐requisite for the expression of familiarity preferences.