http://www.digitaljournal.com/article/57492

Crayfish enact dominance/submission rituals: study

Posted Nov 20, 2006 by KeithLDick

http://today.reuters.com/news/articlenews.aspx?type=scienceNews&storyID=2006-11-20T232338Z_01_N20318675_RTRUKOC_0_US-SCIENCE-CRAYFISH.xml&WTmodLoc=Home-C5-scienceNews-2

Interesting how they display some characteristics of animals higher up the evolutionary chain than them...
"We found that crayfish display such a complex ritual, when two males engaged in pseudocopulatory behavior to signify their dominance relationship," they wrote.
"This was followed by a reduction in aggression and an increased likelihood of the subordinate's survival."