Data for: Northern crayfish form alternation morphometrics

Complex life histories are frequently associated with biological
trade-offs, as the use of one trait can decrease the performance of a
second trait due to the need to balance competing demands to maximize
fitness. Here, we examine growth patterns in invasive adult male northern
crayfish (Faxonius virilis) that are indicative of a potential trade-off
between energy allocation for body size versus chelae size growth.
Northern crayfish undergo cyclic dimorphism, a process characterized by
seasonal morphological changes associated with reproductive status. We
measured carapace length and chelae length before and after molting and
compared these growth increments between the four morphological
transitions of the northern crayfish. Consistent with our predictions,
reproductive crayfish molting to the non-reproductive form and
non-reproductive crayfish molting within the non-reproductive form
experienced a larger carapace length growth increment. Reproductive
crayfish molting within the reproductive form and non-reproductive
crayfish molting to the reproductive form, on the other hand, experienced
a larger growth increment in chelae length. The results of this study
support that cyclic dimorphism evolved as a strategy for optimizing energy
allocation for body and chelae size growth during discrete periods of
reproduction in crayfish with complex life histories.