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Kaluzhnaya OV Belikov SI Schröder HC Wiens M Giovine M Krasko A Müller IM Müller WE 《Die Naturwissenschaften》2005,92(3):134-138
In a preceding study it has been reported that the freshwater sponge Lubomirskia baicalensis, living in Lake Baikal (East Siberia), is composed of spicules forming a characteristic pattern which follows radiate accretive growth. Here we report that the spicules are synthesized by the enzyme silicatein, a protein which is related to cathepsin L. The cDNAs for silicatein and the related cathepsin L were isolated and used as probes to show that the mRNA levels of silicatein in the bases of the spicule skeleton of the animals are low, while the mRNA level of cathepsin L in this region exceeds that of the growing zone. This is the first comprehensive study on the importance of the axial filament/silicatein as an essential structural and functional component determining the growth and stability of demosponge spicules.Note: Sequences from Lubomirskia baicalensis have been deposited in the EMBL/GenBank; cDNAs for the putative silicatein (LBSILICA) are deposited under the accession no. AJ786771 and for cathepsin L (LBCATL) under the accession no. AJ786770. 相似文献
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Handling intensity and the short- and long-term survival of elephant seals: addressing and quantifying research effects on wild animals 总被引:3,自引:0,他引:3
This study addresses the consequences of repeated human handling on the survival of an endangered phocid, the southern elephant seal and the implications for wildlife research. Southern elephant seal pups were repeatedly handled during the first six weeks of their lives. The possibility that such anthropogenic research may have altered the very parameters that were being investigated is a topical and relevant study area that we address here. Our results show that there were no measurable effects on pups that were repeatedly handled and subjected to invasive research methods with respect to survivorship in the short term (the 24-day nursing period) nor in the long term (the first year of life and beyond) and hence fitness one year after handling. In support of this conclusion we were unable to detect any significant differences in the survival rates of the most intensively handled seals and the least intensively handled seals. 相似文献
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The Science of Nature - 相似文献
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Eel populations worldwide are dangerously close to collapsing. Our study is the first to show that current levels of dioxin-like
contaminants are strong candidates because of their devastating effects on development and survival of eel embryos. Female
and male silver eels were artificially stimulated to maturation and reproduction by treatment with carp pituitary extracts
and hCG, respectively. During maturation of female European silver eels, about 60 g fat per kg eel is incorporated in the
oocytes. Together with the fat, however, persistent organic pollutants such as dioxin-like polychlorinated biphenyls (PCBs)
are incorporated too. The total dioxin-like toxic potency of the individual gonad batches was determined as 2,3,7,8-tetrachlorodibenzo-p-dioxine equivalents (TEQs), using an in vitro reporter gene assay. The observed differences in development and survival showed
a significant negative correlation with the TEQ levels in the gonads, already at levels far below the maximal allowable level
for fish consumption, i.e., 4 ng TEQ/kg fish. The clear inverse relationship between the TEQ level and the survival period
of the fertilised eggs strongly suggests that the current levels of dioxin-like compounds seriously impair the reproduction
of the European eel. The peak of the environmental levels of dioxin-like PCBs and the decline of eel coincide worldwide, further
suggesting that, in addition to other threats, these contaminants contributed significantly to the current collapse in eel
populations. 相似文献
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