Otolith elemental fingerprints of juvenile Pacific swordfish Xiphias gladius

The trace element composition of young‐of‐the‐year (YOY) juvenile swordfish Xiphias gladius sagittal otoliths were analysed as a preliminary test of the value of otolith elemental fingerprints for determining swordfish nursery ground origins in the central Pacific Ocean. A suite of five elements (Mg, Zn, Sr, Ba and Pb) was assayed with isotope dilution ICP‐MS; all elemental concentrations were roughly comparable to otoliths of other marine fishes. Multivariate analyses of elemental fingerprints based on Ba and Sr revealed differences between sample sites, and the magnitude of the differences increased with latitudinal separation. With more comprehensive sampling of nursery grounds, it should be possible to identify origin of nursery ground for adult swordfish by analysing the YOY juvenile portion of the sagittal otolith.     

The effect of otolith storage methods on the concentrations of elements detected by laser-ablation ICPMS

Otoliths of male (1+ year old) Terubok, tropical shad Tenualosa toli from the Lupar River, Sarawak, were treated in different ways to assess the effect of post-capture storage on element concentrations in the otolith core and edge detected by laser-ablation inductively coupled plasma mass spectrometry (ICPMS). Five treatments were compared: rapid removal and dry storage; fish kept 5 h after capture then otoliths removed; rapid removal and stored in alcohol; fish rozen for 24 h then otoliths removed; and storage of intact head in alcohol for several weeks. Seven elements were detected at the core and edge of otoliths (Li, Na, Mg, Mn, Co, Sr, Ba). Of these, Na, Mg, Co and Ba differed among treatments, being highest in treatments where the otolith remained in the head. Variation in element measurements due to treatment effects was similar to within-otolith variation for the other elements and was least variable in the fresh treatment. The variation in concentration between the core and edge was more significant than other sources of variation (up to 100 times) for some elements. These differences were probably due to physiological factors (ontogenetic) or to yearly changes in water chemistry. The results indicate that the method of otolith storage, especially freezing whole fish, can have a small, but measurable, effect on the concentrations of Na, Mg, Co and Ba.     

Release of sex steroids into the water by roach

Electro‐olfactogram (EOG) recordings of the olfactory epithelium of both male and female roach Rutilus rutilus demonstrated that both sexes were able to detect free and glucuronidated 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) with high sensitivity. Male, but not female, roach were also sensitive to androstenedione. Sexually mature female roach were shown to release free 17,20β‐P, glucuronidated 17,20β‐P and androstenedione into the water; for all three steroids, the rate of release was significantly enhanced by injection of carp pituitary extract (CPE). A series of trials was also carried out which showed that mature males, and to a lesser extent immature males and females, were able also to release free and glucuronidated 17,20β‐P, both before and after CPE treatment. Water extracts from containers that had held CPE‐treated mature male and female roach were examined for the presence of other steroids. This revealed that free and glucuronidated 17,20β‐P plus free and glucuronidated 17,20β,21‐trihydroxy‐4‐pregnen‐3‐one (17,20β, 21‐P) predominated in water extracts from both sexes. The free moieties of 17,20α‐dihydroxy‐4‐pregnen‐3‐one, 17‐hydroxyprogesterone and 11‐deoxycortisol were found at concentrations which were between four and 20 times lower than those of free 17,20β‐P. Androstenedione was found at concentrations which were 25‐fold lower than those of 17,20β‐P. Despite its apparent high rate of release by sexually mature male and female roach, free 17,20β,21‐P was found not to exhibit any EOG activity at the highest dose tested (10⁻⁷ M).     

Effects of handling and storage methods on the concentrations of elements in deep‐water fish otoliths

Sagittal otoliths of Coryphaenoides rupestris (roundnose grenadier), Helicolenus dactylopterus (bluemouth) and Merluccius merluccius (European hake) were collected using a variety of handling and storage treatments and their elemental composition was examined using inductively coupled plasma mass spectrometry. Some differences between element concentrations were identified between the control and treatment groups, most notably for the element Li. For H. dactylopterus and M. merluccius , Li concentrations were significantly higher in the otoliths extracted with metal forceps and stored in paper envelopes (treatment), compared to those from the same fishes that had been extracted using plastic forceps and stored in polyethylene vials (control). Lower concentrations of Ba and Cr were found in M. merluccius otoliths extracted from fish that had been stored frozen. The presence or absence of elemental concentrations above the instrumental limits of detection was noted, but no significant differences were identified between otolith pairs for any of the treatments. The differences between otolith pairs attributable to storage and handling effects are small compared to between‐area differences.     

Differences of tributyltin accumulation in the masu salmon Oncorhynchus masou between sea‐run and freshwater‐resident types

In order to examine the accumulation pattern of tributyltin (TBT) in relation to the migratory pattern, TBT concentrations in muscles and strontium (Sr) concentrations in otoliths were determined in both sea‐run and freshwater‐resident masu salmon Oncorhynchus masou . Both TBT and Sr concentrations in sea‐run masu salmon were significantly higher than those of freshwater‐residents.     

Migration flexibility between freshwater and marine habitats of the pond smelt Hypomesus nipponensis

The life histories of the pond smelt Hypomesus nipponensis collected from Japanese fresh waters and brackish (sea) waters were studied by examining the strontium (Sr) and calcium (Ca) concentrations in their otoliths. The Sr:Ca ratios in the otoliths changed with the salinity of the habitat. The pond smelt living in a freshwater environment showed consistently low Sr:Ca ratios throughout the otolith, averaging 1·2–1·3 × 10⁻³. These samples were identified as a standard freshwater type. In contrast, fish collected from the intertidal zone showed higher otolith Sr:Ca ratios than those in the standard freshwater type, and the ratios fluctuated along the growth phase. In addition to the two representative life‐history types of H. nipponensis , i. e . freshwater and anadromous life‐history types, other pond smelts were found to have an estuarine resident life history‐type with no freshwater phase, indicating that the pond smelt has a flexible migration strategy with a high degree of behavioural plasticity and an ability to utilize the full range of salinity in its life history.     

Effect of solar radiation (UV and visible) at high altitude on CAM‐cycling and phenolic compound biosynthesis in Sedum album

The field experiment was carried out in order to compare the response of a CAM plant, Sedum album L., to solar radiation at a high altitude (2 100 m) with that at a low altitude location with respect to CAM and phenolic content. Treatment sites included (1) sun‐exposed, low altitude, (2) sun‐exposed, high altitude with different light treatments, including UV‐B and UV‐B + A screening, and (3) shade at high altitude. After a 70‐day treatment period, CAM‐cycling and phenolic compound content were analysed, and high altitude treatments were compared to the low altitude control. The sun‐exposed low altitude control was characterized by CAM‐cycling and a low phenolic compound content during the experiment. In plants transplanted to the high altitude, only the shaded group maintained a CAM‐cycling and a phenolic compound content similar to those of the sun‐exposed low altitude control. Samples under UV‐B and UV‐B + A filters showed similar responses, suggesting the absence of a specific UV‐A radiation effect. The screening of UV‐B or UV‐B + A radiation allowed plants to partially maintain a CAM‐cycling and induced a decrease in phenolic compound content. These responses under UV filters were, however, intermediate between those observed in sun‐exposed and shaded groups. These results demonstrate a specific effect of radiation from both visible (400–800 nm) and UV‐B (280–320 nm) bands on both CAM‐cycling and phenolic biosynthesis in S. album L. plants. These light‐dependent effects are discussed on a physiological basis and a possible interaction between CAM‐cycling and phenolic metabolism is suggested.     

Effect of diet on otolith composition in Pomatomus saltatrix, an estuarine piscivore

To test the hypothesis that elemental composition of otoliths (sagittae) could be influenced by differences in natural prey type, young‐of‐the‐year bluefish Pomatomus saltatrix were captured immediately after their migration from oceanic waters into mid‐Atlantic Bight estuaries and fed either shrimp, Crangon septemspinosa and Palaemonetes spp. or fish Menidia menidia under similar temperature and salinity regimes in two separate 60 day experiments. Unlimited rations of fish and shrimp prey were provided in the first experiment which led to differences in bluefish growth rate between the two prey treatments; fish prey was limited in the second experiment to ensure that growth rates of bluefish in the two prey treatments were similar. Concentrations of seven elements in bluefish otoliths were determined using solution‐based inductively coupled plasma mass spectrometry (ICPMS). There was no significant effect of diet on five of the seven elements examined (Na, Mg, K, Ca and Mn). The levels of Sr and Ba in the otoliths of shrimp‐fed bluefish, however, were significantly higher than fish‐fed bluefish in both experiments. Concentrations of Ba in shrimp‐fed bluefish otoliths were double that found in fish‐fed bluefish. The results suggest that diet can explain some of the variation in otolith chemistry previously attributed to physical and chemical properties of the water.     

Intracellular site of Sr2+ and Ba2+ accumulation in frog twitch muscle fibres as determined by electron probe X-ray microanalysis

Strontium and barium can substitute for calcium at different levels of the excitation-contraction-relaxation cycle. The problem of sequestration of these ions in cellular microcompartments may be settled only by direct evidence obtained with analytical methods. Isolated frog twitch muscle fibres were perfused with increasing concentrations of potassium in Ca-free solution supplemented with Sr2+ (10 mmol/l) or Ba2+ (5 mmol/l). After equilibration in a Ca-free Ringer with Sr2+ or Ba2+ for 30 to 60 min the fibres were frozen in liquid propane (at 80 K) to immobilise ions. Ultrathin (150 nm) cryosections were cut at 170 K, freeze-dried, carbon-coated and analysed in an electron microscope equipped with an X-ray spectrometer. The ultrastructure of the superficial layer of the fibres was satisfactorily preserved. The terminal cisternae (t.c.) of the sarcoplasmic reticulum (SR) were dark and contained various amounts of Sr or Ba in addition to Ca. In Sr loaded fibres the longitudinal SR occasionally showed electron dense content with significant amounts of Ca; no Sr was present. The results suggest that t.c. is the common sequestering compartment for Ca, Sr and Ba. Essentially the same distribution pattern of Sr was found following precipitation of Sr with a solution containing digitonin and Koxalate.     

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.     

Behavioural and electrophysiological responses by reproductive female Neogobius melanostomus to odours released by conspecific males

Behavioural and electrophysiological responses of reproductive and non‐reproductive female round gobies Neogobius melanostomus to water previously occupied by male round gobies (reproductive male water) were compared. Reproductive females spent more time than non‐reproductive females in a tank near the input of water conditioned from reproductive males. Also, reproductive females swam significantly faster than non‐reproductive females, suggesting that reproductive male odour may have activated spawning behaviour. Olfactory epithelial field potential measurement (electro‐olfactogram, EOG) showed that reproductive male water was a potent olfactory stimulus to reproductive females, but not to non‐reproductive females. Reproductive females responded significantly more than non‐reproductive females to solid‐phase (octadecylsilane) extracts of reproductive male water. Also, when these extracts were separated on reverse phase high performance liquid chromatography (HPLC), reproductive females showed noticeably greater responses than non‐reproductive females to the fractions that eluted between 30 and 40 min. The behavioural data support the hypothesis that reproductive male round gobies release compounds into the water that attract potential mates. The EOG data indicate that these compounds can be quantitatively extracted from the water and be partially purified by HPLC. The evidence is not sufficient to indicate whether or not the compounds are steroids. The relatively early elution time on HPLC, however, suggests that if these compounds are steroids, then it is more likely that they will be conjugated rather than free steroids.     

Evaluation of the mobility and discrimination of Ca, Sr and Ba in forest ecosystems: consequence on the use of alkaline-earth element ratios as tracers of Ca

A comprehensive understanding of Ca cycling in an ecosystem is desirable because of the role of this element in tree mineral nutrition and its status as a major base cation on the soil exchange complex. The determination of the origin of Ca in forests is particularly indicated in regard of important changes linked to acid inputs and intensive logging. Natural strontium isotopes are increasingly used as tracers of Ca in forest ecosystems for qualitative and quantitative assessments. Nevertheless this method is limited to relatively simple systems with two sources of nutrients. Some recent studies coupled Sr/Ca or Sr/Ba ratios to Sr isotopic measurements in order to solve more complex systems. Such method has however associated with it some uncertainties: this approach assumed that Ca, Sr and Ba behave similarly throughout the ecosystem and does not take into account the Ca biopurification processes occurring in some tree’s organs which can alter element ratio. The present work focuses on two deciduous species covering large areas in Europe: European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.). In order to test the similarity of behaviour between Ca, Sr and Ba, their concentrations were measured extensively in the major compartments of two forest ecosystems. In parallel, the discrimination process inside tree organs was studied in 23 stands for beech and 10 stands for oak. We found that Sr and Ca behave similarly in all soil and tree compartments. By contrast, Ba and Ca appear to have contrasting behaviours, especially in streams, soil solution and soil exchange complex (no correlations between element concentrations). Sr/Ba and Ba/Ca ratios must therefore be used with care as tracer of Ca. The Ca biopurification is absent in roots and slight in bole wood but is large in bark, twigs and leaves. The discrimination factors (DF) between wood and leaves are characteristic of the two species studied and do not change significantly as a function of the soil Ca status (acidic or calcareous soils). Therefore, strontium–calcium DF can be used as a correction factor of the Sr/Ca ratio of leaves when this ratio is used in connection with Sr isotopic ratios. This correction allows to solve systems of tree nutrition with more than two sources of Ca.     

Effects of temperature and delayed initial feeding on the survival and growth of Japanese flounder larvae

The effects of the timing of initial feeding (0, 1, 2, 3 and 4 days after yolk exhaustion) and temperature (15, 18 and 21° C) on the point‐of‐no‐return (PNR), survival and growth of laboratory‐reared Japanese flounder Paralichthys olivaceus larvae were studied under controlled conditions. The larvae reached PNR on 7·7, 5·2 and 4·2 days‐post‐hatching (dph) at 15, 18 and 21° C, respectively. At each temperature, larval growth did not differ significantly among the delayed initial feedings 1 day before PNR but decreased significantly in larvae first fed after that. In the treatments where initial feeding was equally delayed, larvae grew significantly faster at 18 and 21° C than at 15° C. The larvae survived apparently better at 15 and 18° C than at 21° C when initial feeding was equally delayed. At each temperature, survival of the larvae first fed before PNR did not differ noticeably, while delayed initial feeding after that apparently reduced their survival. These results indicated that there existed a negatively temperature‐dependent PNR in the Japanese flounder larvae. Survival and growth of the larvae strongly depended on temperature as well as the timing of initial feeding. High temperature accelerated the yolk exhaustion and growth of the larvae and thus reduced their starvation tolerance and survival. To avoid potential starvation mortality and obtain good growth, the Japanese flounder larvae must establish successful initial feeding within 2 days after yolk exhaustion at 15° C and within 1 day at both 18 and 21° C.     

Mechanisms of Al‐induced iron chlorosis in wheat (Triticum aestivum). Al‐inhibited biosynthesis and secretion of phytosiderophore

Although Al‐induced iron chlorosis has been observed in many plants, the mechanisms responsible for this phenomenon are yet to be understood. We investigated the effect of Al on iron acquisition in a Strategy II plant, wheat ( Triticum aestivum L.) using both Al‐tolerant (Atlas 66) and ‐sensitive (Scout 66) cultivars. When iron was supplied as insoluble iron, ferric hydroxide, in the culture solution, both cultivars without Al treatment grew normally, while those with 100 µ M AlCl₃ developed chlorosis of the young leaves after 3 days of the treatment. A 21‐h treatment with 100 µ M AlCl₃ in 0.5 m M CaCl₂ solution (pH 4.5) decreased the amount of 2'‐deoxymugineic acid (DMA) secreted by Fe‐deficient Atlas 66 and Scout 66 plants by 85 and 90%, respectively. The amount of DMA secreted decreased with increasing external Al concentrations. Al treatment during the biosynthesis process caused the inhibition of that of DMA within 3 h. The secretion process was also found to be inhibited by Al, resulting in the biosynthesized DMA remaining in the roots. These results demonstrate the inhibition by Al of both biosynthesis and secretion of DMA attributed to Al‐induced iron chlorosis.     

A Nicotiana plumbaginifolia protein labeled with an azido cytokinin agonist is a glutathione S‐transferase

The mechanisms of reception/transduction of cytokinins still remain largely unknown. We used 1‐(2‐azido‐6‐chloropyrid‐4‐yl)‐3‐(4‐[³H])phenylurea ([³H]azido‐CPPU), a new photoaffinity probe to search for cytokinin‐binding proteins. A soluble protein that binds phenylurea‐type cytokinins has been specifically photolabeled in Nicotiana plumbaginifolia (cv. Viviani line pbH1D) leaf extracts. The protein was purified to homogeneity by affinity chromatography. Its N‐terminal amino acid sequence, as well as four internal peptidic sequences are highly homologous with the theta class of the glutathione S‐transferase superfamily (GST, EC 2.5.1.18) including Hyoscyamus muticus and Arabidopsis GSTs identified as auxin‐binding proteins. The purified N. plumbaginifolia protein also possesses GST enzymatic activity. To test the possible involvement of this GST in the mechanism of action of cytokinin, we studied the binding of tritiated‐CPPU to the purified GST in the presence of various compounds, cytokinin agonists, cytokinin antagonists, or inactive molecules. Thidiazuron is a poor competitor, and neither zeatin nor the active optical isomer R‐MeBA is able to inhibit the binding of CPPU. There is no correlation between the cytokinin activity and the binding properties of the molecules tested. Our results confirmed that plant GSTs bind different compounds, especially plant hormones but probably have no specific role in the mode of action of cytokinins.     

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.     

Blue light‐induced apoplastic acidification of Arabidopsis thaliana guard cells: Inhibition by ABA is mediated through protein phosphatases

The phytohormone abscisic acid (ABA) inhibits blue light‐induced apoplastic acidification of guard cells. The signal transduction pathway of ABA, mediating this response, was studied using ABA‐insensitive ( abi ) mutants of Arabidopsis thaliana . Apoplastic acidification was monitored with a flat tipped pH‐electrode placed on epidermal strips, in which only guard cells were viable. Blue light‐induced apoplastic acidification was reduced by vanadate and diethylstilbestrol (DES), indicating involvement of plasma membrane‐bound H⁺‐ATPases. In wild type epidermal strips, ABA reduced blue light‐induced acidification to 63%. The inhibition did not result from an increased cytoplasmic free Ca²⁺ concentration in guard cells, since factors that increase the Ca²⁺ concentration stimulated apoplastic acidification. Apoplastic acidification was not inhibited by ABA in abi1 and abi2 mutants. In abi1 epidermal strips ABA had no effect on the acidification rate, while it stimulated apoplastic acidification in abi2 . The ABA response in both mutants could be partially restored with protein kinase and phosphatase inhibitors. The abi1 guard cells became ABA responsive in the presence of okadaic acid, a protein phosphatase inhibitor. In abi2 guard cells the wild type ABA response was partially restored by K‐252a, a protein kinase inhibitor. Apoplastic inhibition is thus mediated through the protein phosphatases encoded by ABI1 and ABI2 . The results with protein kinase and protein phosphatase inhibitors indicate that ABI1 and ABI2 are involved in separate signal transduction pathways.     

Serum levels of testosterone, 11‐ketotestosterone and oestradiol‐17β in three species of sturgeon during gonadal development and final maturation induced by hormonal treatment

Changes in serum concentrations of two androgens, testosterone (T) and 11‐ketotestosterone (11KT), and oestradiol‐17β(E2) in male and female giant sturgeon Huso huso , Russian sturgeon Acipenser gueldenstaedtii and stellate sturgeon Acipenser stellatus were studied at different stages of gonadal maturity and after final maturation induced by hormonal treatment. Both male and female fish displayed a distinct increase in serum steroid concentrations during gonadal development. 11KT levels were significantly higher in males than females, with a positive correlation detected between 11KT and T concentrations. In maturing males and females, higher values of both 11KT and T were observed in stellate sturgeon compared to giant and Russian sturgeons. Vitellogenesis and high E2 levels were correlated in maturing sturgeon females.