The Timing of Larval Release
The timing of larval release within reproductive seasons is synchronized by shorter environmental periodicities, including light-dark, lunar, tidal, and tidal amplitude cycles. Endogenous timing of larval release may be demonstrated by identifying free-running rhythms and entraining agents. Several methods have been used to determine the timing of larval release by animals in natural populations. Explanations for the evolution of synchronous larval release are rife, but most share the underlying tenet that larval release converges around safe periods when survival of females, embryos, larvae, or settlers is enhanced. The plethora of untested hypotheses attests to the difficulty of demonstrating that synchronous release evolves in response to predictable gradients of selective agents. Female crabs attach fertilized eggs beneath their abdomens and often incubate eggs in refuges until they release larvae. The timing of larval release may be controlled by females or embryos. The timing of larval release by intertidal and shallow subtidal crabs varies across tidal regimes.