Data from: Morphology, performance and fluid dynamics of the crayfish escape response

Sexual selection can result in an exaggerated morphology that constrains
locomotor performance. We studied the relationship between morphology and
the tail-flip escape response in male and female rusty crayfish (Faxonius
rusticus), a species in which males have enlarged claws (chelae). We found
that females had wider abdomens and longer uropods (terminal appendage of
the tail fan) than males, while males possessed deeper abdomens and larger
chelae, relative to total length. Chelae size was negatively associated
with escape velocity, whereas longer abdomens and uropods were positively
associated with escape velocity. We found no sex-specific differences in
maximum force generated during the tail flip, but uropod length was
strongly, positively correlated with tail-flip force in males. Particle
image velocimetry (PIV) revealed that the formation of a vortex, rather
than the expulsion of fluid between two closing body surfaces, generates
propulsion in rusty crayfish. PIV also revealed that the pleopods (ventral
abdominal appendages) contribute to the momentum generated by the tail. To
our knowledge, this is the first confirmation of vortex formation in a
decapod crustacean.