Abstract:
Hyperiid amphipods are open ocean crustaceans which use gelatinous
planktonic animals for food, shelter, and brooding space for their offspring.
These associations involve varying degrees of host specificity; and there are
few obvious correlations between gross morphology of the amphipods and
the types of host they choose. The mechanisms which allow hyperiids to find
and select specific hosts in the water column were investigated through the
sensory and behavioral basis of these symbioses in three genera of hyperiids,
Vibilia, Lycaea, and Phronima, which differ in the nature of their
association with a common host - salps. The investigation included the
description of the distribution and morphology of sensilla on the dorsal
surface of the exoskeleton and antennules of the three genera of hyperiids
with speculation on their functions. The ultrastructure of the aesthetasc.
sensilla of Vibilia sp. was determined for comparison with other crustacean
aesthetasc sensilla, making a chemosensory function plausible. Behavioral
experiments were conducted at sea which demonstrated a chemosensory basis
for the host-specific associations between species of Vibilia and Lycaea and
salps. Observations on the internal anatomy and behavior of Phronima are
described which underscore the importance of salps to their general ecology.
