Literaturdatenbank
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Dunson, W. A. (1985). Effect of water salinity and food salt content on growth and sodium efflux of hatchling diamondback terrapins (malaclemys). Physiological zoology, 58(6), 736–747.
Added by: Admin (24 Aug 2008 18:46:23 UTC) |
| Resource type: Journal Article BibTeX citation key: Dunson1985 View all bibliographic details  |
Categories: General Keywords: Ernährung = nutrition, Morphologie = morphology, Physiologie = physiology, Schildkröten = turtles + tortoises Creators: Dunson Collection: Physiological zoology |
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| Abstract |
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At hatching and for many months afterward (until they reach about 50 g), diamondback terrapins cannot grow in salinities above about two-thirds seawater. Yet salinities and offered one drink of fresh water every 2 wk can achieve limited growth. In 25% seawater at 28 C, growth of hatching terrapins is stimulated in comparison with animals is fresh water or 50% seawater. Hatchlings grown in 0.25 Molal glycerol solutions, osmotically similar to 25% seawater, have the same growth rates as those in fresh water. Hatchling terrapins injected with NaCl have an elevated rate of sodium efflux (about 65 .mu.mol/100 g wet mass .cntdot. h), indicating that the lachrymal salt glands are functional. At hatching, body water content (77.0%) is much higher than that of adults (64.5%), and body sodium concentration (.mu.ol/g dry mass) is slightly higher. However, sodium concentration in units of .mu.ol/g wet mass is only 71% of adult levels. When feeding commences, body sodium concentration (as .mu.mol/g wet mass) rises to adult levels. Further increases occur in salinities up to 50% seawater. There is an inverse relation between body size and water efflux in 100% seawater, and this difference appears to be one cause of the lesser tolerance of smaller terrapins to saline water. In contrast, sodium influx in hatchlings is only slightly elevated. The rate of sodium efflux in fed terrapins is directly correlated with feeding rate. However, the main source of sodium uptake at higher salinities appears to be incidental swallowing of water during ingestion of food-not the salt content of the food itself.
Added by: Admin |