Suspension feeding in marine sponges Halichondria panicea and Haliclona urceolus:effects of temperature on filtration rate and energy cost of pumping

Abstract

Filtration rate (measured as clearance of algal cells) was measured at different temperatures in the sponge Halichondna panicea. An increase in water temperature from 6 to 12 "C caused the mean flltration rate to increase 4.3 * 2.3 tlmes. Thls value was higher than previously found for other marine ciliary suspension-feeding anlmals. Filtration rate at 12 "C was also measured in Haliclona urceolus by means of a n indirect clearance method In addition to a direct technique for measuring pumping rate. It was found that the 2 sponge specles had near-identical flltration rates, with maximum rates of approximately 60 m1 m ~n ' (g dry weight).' at 12 T. The normal pump pressure, or operating point 0,, of a standard sponge (based on our own measurements and calculat~ons from l~terature data for a 0.1 g dry weight Haliclona sp.) was estimated as the sum of maln contributions to head losses along the flow path from entry (ostia) to exit (osculum) The head losses were as follows: ostia 0.0373 mm H,O, inhalant canal 0 1205 to 0.013 mm H,O, prosopyles 0.1153 to 0 02321 mm H,O, collar-fllter 0.122 mm H,O; exhalant canals = inhalant canals; and osculum 0.1576 mm H20. The (maximal) 0, was found to be 0 673 mm H,O and the power output P, from the sponge pump was 0.677 pW. The pump work, defined as P,R.' where R is the respiratory output, was 0.85 % The low energy cost of filtration and the temperature effect are discussed and compared w ~t h recent data for other ciliary suspension feeders. It is argued that passive current-induced filtration may be of insignificant importance for sponges.