Water and sodium balance in the estuarine diamondback terrapin (Malaclemys)

摘要: Total body water decreased significantly in terrapins exposed to sea (SW). Although the intracellular fluid somewhat upon SW exposure, decline extracellular was almost twice as great. Under conditions of voluntary drinking after salt loading, substantially increased volume while maintaining near freshwater (FW) control levels. FW were consistently heavier than animals same plastron length SW. Thus expression volumes ml/cm rather % weight is necessary correct for loss total with progressive dehydration. Fasted lost at 0.32% weight/day, whereas rate 0.21%/day. Water influx and efflux 0.17 0.16 ml/100 g·h respectively. When by calculated value unmeasured respiratory loss, it exceeded influex 0.01 g·h. Consequently net determined radiotracers (equivalent 0.24% weight/day) similar difference between losses (0.11%/day). Partitioning studies indicated that majority exchange terrapin occurs through integument. Terrapins underwent a concentration fluids, most which can be attributed not electrolyte gain. The rates Na quite low (usually ranging from 6–10 μmoles/100 g·h). In two injection NaCl loads resulted eight- 19-fold increases efflux. uptake occurred orally. skin virtually impermeable Na. gland possibly cloaca major routes an increase cephalic excretion mean 3.2 32.5 exhibited significant bladder urine [K] over controls. There direct relationship plasma [Na], [K], lachrymal Na−K ATPase content. comparing painted turtles (Chrysemys) radiotracer demonstrated similarity influx, but there least four-fold turtle. It seems likely skins many aquatic reptiles (marine, estuarine FW) are differ markedly permeability.