Salt gland blood flow in the hatchling green turtle, Chelonia mydas
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Microsphere and morphometric techniques were used to investigate any circulatory changes that accompany secretion by the salt glands of hatchling Chelonia mydas. Salt glands were activated by a salt load of 27.0 mmol NaCl kg body mass (BM)−1, resulting in a mean sodium secretion rate of 4.14 ± 0.11 mmol Na kg BM−1 h−1 for a single gland. Microsphere entrapment was approximately 160–180 times greater in the active salt gland than the inactive gland, inferring a similar change in blood flow through salt gland capillaries. The concentration of microspheres trapped in the salt gland was significantly correlated with the rate of tear production (ml kg BM−1 h−1) and the total rate of sodium secretion (mmol Na kg BM−1 h−1) but not with tear sodium concentration (mmol Na l−1). Adrenaline (500 μg kg BM−1) inhibited tear production within 2 min and reduced microsphere entrapment by approximately 95% compared with active glands. The volume of filled blood vessels increased from 0.03 ± 0.01% of secretory lobe volume in inactive salt gland sections to 0.70 ± 0.11% in active gland sections. The results demonstrate that capillary blood flow in the salt gland of C. mydas can regulate the activity of the gland as a whole.
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