, Volume 9, Issue 1, pp 38-50

In situ pumping activities of tropical Demospongiae

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Abstract

Studies employing Scuba techniques were carried out on populations of 3 species of tropical demosponges to determine in situ patterns of water-pumping activity. Short-term changes in individual activity of deep-water species (15 to 55 m) were determined from continuous recordings of exhalant current velocities. Long-term changes were determined by repeated measurements of oscular velocity and oscular area. Mycale sp. was found to maintain constant levels of pumping activity in both short and long-term studies. Verongia gigantea underwent periodic cessations of activity averaging 42 min, at random intervals of approximately 19 h. Cessations were asynchronous throughout the population and inherent in origin. Long-term activity variations appeared to be cyclic, but were explainable by environmental events. Shallow-water populations of Tethya crypta exhibited a synchronized diurnal cycle of contraction and dilation, probably tied to the diurnal cycle of illumination. A longer term (average 15.8 days) cycle of activity-inactivity, also involving contraction and dilation, was asynchronous throughout the population during the calm season. Each individual maintained a fairly uniform cyclic period ranging from 9 to 21 days. Changes of T. crypta activity were probably due to changes in flagellar activity. With the onset of the stormy season, the activity of all members of the population was brought into synchrony by the effects of approximately biweekly storms. The behavior of Verongia archeri, Agelas sp., and other species indicates that constant activity (e.g. Mycale sp.) may be restricted to thin-walled species working at low pressures and velocities. Activity patterns are consistent within species, but variable in higher taxa. Behavioral activity patterns of sponges must be taken into account in ecological and physiological studies of these animals.

Communicated by J. Bunt, Miami