IT ONLY takes one crayfish to empty its bladder and the rest scurry away. The
urine is a warning signal to other crayfish.
Aquatic arthropods excrete most of their body waste through their gills, so
no one knew what the bladder was for. Rebecca Zulandt Schneider and Paul Moore
of Bowling Green State University in Ohio attached catheters to crayfish either
in tanks of their own or with a largemouth bass.
Only the crayfish that were frightened by the bass emptied their bladders
(Journal of Experimental Biology (vol 203, p 765). And when the
researchers tipped the urine into…
