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  • 1
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The newly recruited Japanese eel, Anguilla japonica, elvers and 1-year-old eels collected in estuaries and in rivers, respectively, were studied. The microstructure and chemical composition of the sagittal otolith of these eels were examined by SEM and wavelength-dispersive spectrometer (WDS), A transition zone or‘elver mark’was observed in the otolith of the young eels. A comparison of the otoliths of elvers with those from the 1-year-old eels suggests that this transition zone was deposited during upstream migration, a change from a marine to freshwater environment. Strontium (Sr) content in the primordium of the otolith of both elvers and young eels was low, probably due to the maternal or freshwater origin of the oocyte. The concentration of Sr in the otolith increased gradually during marine life and reached a peak approximately 1 month before upstream migration. As the elvers entered the estuary, the Src concentration dramatically decreased and remained at a low level thereafter. These findings indicate that the history of the migratory environment of the eel can be reconstructed from a combined study of otolith microstructure and microchemistry analysis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To test the hypothesis that the Japanese eel, Anguillu japonica, elvers in the eastern and western coasts of Taiwan are recruited from two different spawning grounds and to increase the knowledge of the early life history of the eel, the otolith microstructure and daily age of elvers collected from five estuaries in the coast of Taiwan during December 1989 through February 1990 were examined by scanning electron microscopy. The total length of elvers at arrival in the estuaries was similar among estuaries, averaging c. 56.0 mm and showed a seasonal decrease. The maximum radius of the sagittal otolith of elvers ranged from 124.46 to 181.82μm with a mean of 143.15 ± 12.72 μm. The otolith from centre to edge included an organic-rich primordium (9.20 ± 2.02 μm in diameter), a diffusively calcified core (20.94 ± 1.99 μm), and the daily growth increments; these three layers were probably deposited during the embryonic, yolk sac and feeding period respectively. The growth rate of the otolith was higher at the beginning of early life (0.5−1.0 μm day −1), lowest at approximately 100-days old (〈0.5 μm day−1), and highest 1 month before arrival at the estuary (〉 1.0 pm day−1). The mean age for elvers arriving in the estuaries of the coasts of Taiwan was approximately 170.4 ± 21.02 days. Neither the growth pattern of the otolith nor the age of elvers arriving in the estuary were significantly different among estuaries, indicating that the elvers in both eastern and western Taiwan were probably recruited from the same spawning ground. The growth pattern of the otolith in relation to larval migration was analysed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Mesophyll protoplasts from Brassica oleracea, B. napus, Nicotiana tobaccum and Solanum tuberosum were isolated and subjected to uttracentrifugation at 65000g for 30 min in percoll solutions containing various strengths of salt and osmotic stabilizing agents. After centrifugation, the self-generated percoll gradients were evaluated for their effectiveness in protoplast evacuolation and enucleation. The vacuoles, cell debris, evacuolated protoplasts and enucleated protoplasts were separated. Factors that affected evacuolation and enucleation in the percoll gradients were described. Mesophyll protoplasts produced by epidermis peeling and short enzyme incubation periods were more easily evacuolated and enucleated than those produced by leaf-slicing and long incubation periods. Lower centrifugal force at 25000g for 80 min was also successful in evacuolating and enucleating the mesophyll protoplasts. A green band that contained nearly pure evacuolated protoplasts, of which 45% were enucleated protoplasts, was obtained from the self-generated percoll gradient. Rhodamine 123 staining of mitochondria indicated that the evacuolated protoplasts were metabolically active and were capable of regenerating the vacuole and cell wall. Cell divisions were also observed when the evacuolated protoplasts were cultured.
    Type of Medium: Electronic Resource
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