Behavior and Locomotion During the Dispersal Phase of Larval Life
This chapter summarizes the ways that larvae respond behaviorally to the biotic and abiotic attributes of their environment while swimming. Most larvae are heavier than seawater and sink when swimming ceases. Some slow their rate of sinking by increasing drag with large feathery appendages, long setae, or neutrally buoyant shells. Larval behavior requires that larvae control the direction, frequency, and/or speed of swimming. A major function of larval locomotion is to control the position of larvae in the water column. This sort of behavioral control allows larvae to avoid predation, optimize feeding, increase or decrease dispersal distance, and maximize or minimize spread with respect to both siblings and parents. Behavioral defense mechanisms have been reviewed by Young and F. S. Chia and by E. Morgan. Some ciliated larvae apparently escape predators by ciliary reversal. Vertical migration is perhaps the best studied aspect of larval behavior under field conditions.