Gravel in the disgestive tract of axolotls.

[umbjork1 at cc.UManitoba.CA]

We recently completed an x-ray series of five animals during limb 
regeneration. As a serendiptous side discovery we noted that the animals 
are regularly taking in gravel. We estimate these adults have about 10 
grams of rock of various sizes (3 mm to 1 cm) at any one time. These rocks 
are moving through the digestive system throughout the x-rays series. We 
began monitoring the animals excretions and discovered the gravel is passed 
regularly in the normal waste. 

We are wondering if this represents a pathogenic concern or do wild 
salamanders take in gravel normally? If they are taking gravel on purpose, 
are the animals using the gravel as ballast? Are they using the gravel the 
way a bird's gizzard works? Is the intake of gravel in our animals an 
effect of the artifical environment we keep them in? (We use and under 
gravel filtration system.) Our animals seem to be in perfect health, 
spawn naturally and frequently, and our larvae grow rapidly.

Any comments appreciated.

Natalie K Bjorklund
University of Manitoba's Colony