The sensory mediation of symbiosis between hyperiid amphipods and salps

Hyperiid amphipods are open ocean crustaceans which use gelatinousplanktonic animals for food, shelter, and brooding space for their offspring.These associations involve varying degrees of host specificity; and there arefew obvious correlations between gross morphology of the amphipods andthe types of host they choose. The mechanisms which allow hyperiids to findand select specific hosts in the water column were investigated through thesensory and behavioral basis of these symbioses in three genera of hyperiids,Vibilia, Lycaea, and Phronima, which differ in the nature of theirassociation with a common host - salps. The investigation included thedescription of the distribution and morphology of sensilla on the dorsalsurface of the exoskeleton and antennules of the three genera of hyperiidswith speculation on their functions. The ultrastructure of the aesthetasc.sensilla of Vibilia sp. was determined for comparison with other crustaceanaesthetasc sensilla, making a chemosensory function plausible. Behavioralexperiments were conducted at sea which demonstrated a chemosensory basisfor the host-specific associations between species of Vibilia and Lycaea andsalps. Observations on the internal anatomy and behavior of Phronima aredescribed which underscore the importance of salps to their general ecology.

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution March 1988