Abstract:
Diadora aspera is an intertidal keyhole limpet found in the mid-tidal
zone. Its activity pattern was estimated under laboratory
conditions using time-lapse-photography and manometric determinations
of oxygen consumption.
Statistical and computer analyses of the photographic data suggest
the presence of both a 24 hour and a 12-13 hour rhythm in activity.
Both oxygen consumption and photographic data suggest that the diel
rhythm has an activity peak at noon. The oxygen consumption data also
suggest that the 12-13 hour rhythm in activity is peaked 3-4 hours
before high tide. Protection from predation (possibly by Pycnopodia
helianthoides) is suggested as a possible factor in selection for this
phasing.
