The physiological, behavioral, and ecological responses of nocturnal marine fauna to benthic invertebrate bioluminescence

The predominant type of luminescent signals in coastal marine environments are rapid flashes that are produced by benthic invertebrates. These species only produce light when they are mechanically stimulated. The intensity and duration of the flash are directly proportional to the strength of the stimulus. These flash characteristics, along with the poor visual abilities of the emitting species, suggest that the luminescence functions to deter predators. This dissertation utilized behavioral studies in the field, and physiological studies in the laboratory to address the mechanisms and functions of these contact elicited luminescent signals emitted from coastal benthic invertebrates.;Field studies demonstrated that luminescence produced by the Caribbean brittle-star Ophiopsila riisei functions as an aposematic signal to deter portunid crab predators. The luminescent signals warn crabs of the unpalatability of the brittle-stars. Additionally, brittle-star luminescence elicited avoidance behaviors from a variety of other large nocturnal predators (octopus, shrimp, fish, and crabs), while smaller, non-predators species (shrimps and crabs) showed minimal responses to the luminescent signals. The differential effects of luminescence on predator and prey species may have important effects on structuring nocturnal marine communities. Finally, the luminescent predator deterrent is a key feature that allows suspension feeding brittle-stars to maximize their feeding time and minimize mortality and sublethal damage resulting from predation events.;Laboratory experiments on the temperate portunid crab Portunus xantusii showed that luminescence produced by the sea pansy Renilla kollikeri also elicits avoidance behaviors or startle responses from crabs. The production of startle behaviors was correlated with a rapid and brief decrease in heart rate. This optocardial reflex provides a reliable physiological indicator of the subsequent behavioral responses. Further experiments used this reflex as a bioassay to demonstrate that crabs are most responsive to light stimuli which have the color, train duration, pulse rate, pulse duration, and interpulse interval that are characteristic of the trains of luminescent signals produced by benthic coastal organisms. It appears that both luminescent invertebrates and nocturnal predators from coastal marine communities have evolved convergent adaptions that provide for the efficient production and reception of these luminescent signals.