Re: Guide for anti-AATers

chris brochu (gator@mail.utexas.edu)
20 Oct 1995 03:36:38 GMT

In article <hubey.814066596@pegasus.montclair.edu> H. M. Hubey,
hubey@pegasus.montclair.edu writes:
>Anything that gets rid of salt can be a salt excretion mechanism.
>I agree that unless they wept a lot it would be ineffective,
>certainly not as effective as kidneys or sweating but so what.
>

This is something for which comparative data actually exist, sort of.

As I stated in an earlier post, crocodylians regulate salt overload with
glands in their mouth. Several studies have shown that the fluid coming
from these glands is much more saline than normal body fluid. Sea
turtles show something similar, but this does not appear to be a general
reptilian trait.

If our tear ducts were behaving like croc salt glands, we would expect
them to excrete hypersaline fluid, and they don't.

BTW the amount of water lost via tears is negligible.

Franklin, C.E., and C.. Grigg, 1993. Increased vascularity of the
lingual salt glands of the estuarine crocodile Crocodylus porosus kept in
hyperosmotic salinity. J. Morphology, 218:143-151.

Marshall, A.T., and P.D. Cooper, 1988. Secretory capacity of the
lachrymal salt gland ofhatchling sea turtles, Chelonia mydas. J. Comp.
Phys. (b), 157:821-827.

Mazzotti, F.J., and W.A. Dunson, 1984. Adaptations of Crocodylus acutus
and Alligator for life in saline water.

Taylor, G.C., C.E. Franklin, and G.C. Grigg, 1995. Salt loading
stimulates secretion by the lingual salt glands in unrestrained
Crocodylus porosus. Jour. Exp. Zool. 272:490-495.

Taplin, L.E., 1988. Osmoregulation in crocodilians. Biological Review,
63:333-377.

Taplin, L.E., and G.C. Grigg, 1981. Salt glands in the tongue of the
estuarine crocodile, Crocodylus porosus. Science, 212:1045-1047.

Taplin, L.E., G.C. Grigg, P. Harlow, T.M. Ellis, and W.A. Dunson, 1982.
Lingual salt glands in Crocodylus acutus and C. johnstoni and their
absence from Alligator mississippiensis and Caiman crocodilus. J. Comp.
Phys. (A) 149:43-47.

Taplin, L.E., G.C. Grigg, and L. Beard, 1985. Salt gland function in
fresh water crocodiles: evidence for a marine phase in eusuchian
evolution? pp. 403-410 in Biology of Australasian Frogs and Reptiles,
ed. G.C. Grigg, R. Shine, and H. Ehmann, Surrey Beatty and Sons, Sydney.

Taplin, L.E., ad G.C. Grigg, 1989. Historical biogeography of the
eusuchian crocodilians: a physiological perspective. American
Zoologist, 29:885-901.

This is not an exhaustive list, and in particular the bibliography in
Taylor et al. is useful. There is also a paper by Kate Jackson and
coauthors in press in Biol. Jour. Linn. Soc., but since it's not out yet,
I won't spread the title.

chris