Sodium balance in the American alligator

Abstract

Alligators in fresh water regulate their plasma and cloacal fluid electrolytes at concentrations similar to those of other crocodilians. They have an exchangeable Na pool of 60.8 pmol/gm and a unidirectional Na efflux of 3.9 pmol/100 gm-hr. Of this 11% is excreted from the cloaca, 43% presumably diffuses across the body integument, and the remaining 46% is lost from the head region. The integumental Na efflux is estimated to be 0.01 pmol/cm2 Shr. In fresh water the net flux is 0.5 pmo1/100 gm.hr, which suggests that nondietary Na uptake can compensate for 86% of unidirectional Na loss.

Effects of chronic exposure to 12‰ saltwater on the endocrine physiology of juvenile American alligator (Alligator mississippiensis)

“…Reptile kidney nephrons do not possess a Loop of Henle (Braun, 1998;Willmer et al, 2009) and hence are unable to excrete hyperosmotic urine. Furthermore, although only a few studies have determined alligatorid integumental permeability to Na + , there is evidence of Na + influx and efflux across the integument when alligators are in FW (Ellis and Evans, 1984;Taplin, 1988). Data further show influx of Na + across the integument when alligators are exposed to 35‰ for a few hours (Mazzotti and Dunson, 1984).…”

Correlations between environmental salinity levels, blood biochemistry parameters, and steroid hormones in wild juvenile American alligators (Alligator mississippiensis)

“…For example, unfed alligators ranging in size from 310–586 g showed an average Na + influx of ~ 10.8 μmol 100 g −1 h −1 when exposed to 35‰ for up to 4 h (while water efflux was 0.25 ml 100 g −1 h −1 ) 51 . Freshwater also has significant effects on electrolyte balance, as net Na + and K + loss occurs in solutions up to 1 mmol L −1 Na + and 0.4 mmol L −1 K + in freshwater 52 , 53 . Additionally, hatchlings (0.03–0.07 g) exhibit a whole-body Na + efflux of 3.9 μmol 100 g −1 h −1 in freshwater 52 .…”

“…Freshwater also has significant effects on electrolyte balance, as net Na + and K + loss occurs in solutions up to 1 mmol L −1 Na + and 0.4 mmol L −1 K + in freshwater 52 , 53 . Additionally, hatchlings (0.03–0.07 g) exhibit a whole-body Na + efflux of 3.9 μmol 100 g −1 h −1 in freshwater 52 . Thus, as alligator integument is not impermeable to fluxes of electrolytes, the positive and significant correlations in wild alligators are therefore likely due to passive influx of ions through the integument and mucous membranes, while water loss also contributed to elevated ion levels as seen in laboratory-kept alligators 5 .…”

Diversity and dispersal trends following the latest-permian mass extinction

“…Crocodyloids and gavialoids also possess a keratinized surface to their buccal cavity (tongue and palate) that likely serves to decrease oral permeability and reduce water exchange with the environment (Taplin and Grigg, 1989). Additionally, the integument of alligatoroids is more permeable to fluids than the integument of crocodylines (Ellis and Evans, 1984;Taplin, 1988).…”