Abstract:
The chelipeds of Orconectes rusticus are sexually
dimorphic; males possessing the larger. Males use their chelae in
intermale aggressive interactions, both to threaten, and assault
opp,onents. In dyadic interactions males with larger chelae were
dominant over otherwise physically similar opponents. A high
frequency of attack behaviour, coupled with a low frequency of
threats during these interactions indicates that actual physical
contact is required for opponent assessment.
Large clawed males oriented females into the copulatory
position faster than small clawed males. Females more
frequently escaped the precopulatory-grasp attempts of small
clawed males. Additionally, male-female pairs that included a
large clawed male remained in copula longer than pairs that
included a small clawed male. Sperm of the second male to mate
took precedence over the sperm of the primary male. Sperm
precedence was incomplete; about 900/0 paternity accrued to the
second male.
