In situ pumping activity of the sponge Aplysina aerophoba, Nardo 1886

Abstract

Aplysina aerophoba, Nardo 1886 is a common and well examined demosponge in the Mediterranean Sea. For sponges, as sessile, inner filter feeders, the most important function is pumping water through their canal system. This flow through is actively generated, supplies the sponge with oxygen and food particles and washes out waste products. Oxygen measurements ex situ, as a given example, show high oxygen saturations inside pumping sponges and oxygen depletion in non-pumping sponges. Thus, the oxygen situation within the sponge, like the food particle supply, waste washout and others, are directly related to its active pumping. To learn more about the poriferan function, it is important to know more about its undisturbed in situ pumping activity and consequently about the correlated conditions inside the sponge body. We conducted a tracer experiment in situ and tested sponge activity in terms of active pumping. Our technique excluded stress and disturbance to the sponges, hence minimizing experimental artefacts. The results show Aplysina aerophoba to be permanently pumping, which is implying a permanent supply of oxygen and of course food particles as well as a permanent washout of waste products and a permanent, presumably high energy consumption. We therefore conclude, that Aplysina aerophoba is always well supplied with oxygen, and that tissue anoxia or anaerobic metabolisms are of no significant importance in this sponge species. This fact of a permanent flow through in sponges will have to be taken into account for past and future hypotheses on the physiology of the sponge-microbial systems.