The energetic cost of filtration by demosponges and their behavioural response to ambient currents

Abstract

There was an error published in J. Exp. Biol. 220, 995-1007. Some values for head loss and respiration in Table 3 were carried over from an earlier version of the manuscript. The corrected table follows.The final numbers for volume flow rate, head loss, pumping power and cost of pumping remain unchanged, and there are no changes to the results and conclusions of the paper. The data available from the University of Alberta Education Resource Archive (ERA; https://doi.org/ 10.7939/R36688W8N) are correct. The authors apologise for any inconvenience this may have caused. 4743© 2017. Published by The Company of Biologists Ltd | Journal of Experimental Biology (2017) 220, 4743-4744 doi:10.1242 Journal of Experimental Biology ΔH and measured volume flow rate are used to calculate the pumping power P p using Eqn A6. The cost of pumping η (%) is then estimated using Eqn A7 from the pumping power P p and the measured respiration rate R tot . The collar slit is in bold, representing the filtration apparatus. Journal of Experimental Biology (2017) 220, 4743-4744 doi:10.1242 Journal of Experimental Biology ABSTRACT Sponges (Porifera) are abundant in most marine and freshwater ecosystems, and as suspension feeders they play a crucial role in filtering the water column. Their active pumping enables them to filter up to 900 times their body volume of water per hour, recycling nutrients and coupling a pelagic food supply with benthic communities. Despite the ecological importance of sponge filter feeding, little is known about how sponges control the water flow through their canal system or how much energy it costs to filter the water. Sponges have long been considered textbook examples of animals that use current-induced flow. We provide evidence that suggests that some species of demosponge do not use currentinduced flow; rather, they respond behaviourally to increased ambient currents by reducing the volume of water filtered. Using a morphometric model of the canal system, we also show that filter feeding may be more energetically costly than previously thought. Measurements of volumetric flow rates and oxygen removal in five species of demosponge show that pumping rates are variable within and between species, with the more oxygen consumed the greater the volume filtered. Together, these data suggest that sponges have active control over the volume of water they process, which may be an adaptation to reduce the energetic cost of filtration in times of high stress. 4744 CORRECTION

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