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| Home > Publications database > Fluid dynamics and flow in leucon-type sponge canal systems: Insights from the freshwater sponge $\textit{Spongilla lacustris}$ |
| Home > Publications database > Fluid dynamics and flow in leucon-type sponge canal systems: Insights from the freshwater sponge $\textit{Spongilla lacustris}$ |
| Conference Presentation | DESY-2014-02138 |
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2013
Abstract: As sessile filter feeding animals sponges (Porifera) rely on highly efficient fluid transport systems to keep energy expenditure low. As a consequence of the high complexity of the canal system network in leucon-type aquiferous systems only limited data on flow velocities and transport rates are available to date. Obtaining unaltered experimental measurements from internal parts of the canal system is almost impossible. Therefore data for e.g. choanocytes or canal segments of different hierarchical levels are mainly based on theoretical assumptions. This is mainly due to the limited availability of morphometric and quantitative data on canal system architecture. In our study we used the fresh water sponge Spongilla lacustris which as a juvenile is an ideal model system to study flow in sponge. Due to its transparency flow velocities can be determined experimentally inside canals near the surface and at the osculum. The limited architectural complexity and small body size enables the extraction of 3D canal system models from single specimens based on SR-µCT data. Flow through the canal system was studied using a finite element modeling approach. In order to calibrate our model and verify the results of our modeling approach we conducted flow velocity measurements by particle tracking velocimetry on 10 – 14 d old hatched specimens. In order to measure flow in canal segments of the incurrent and excurrent canal system we used sandwich cultures of S. lacustris. Observed flow velocities in canal segments of different hierarchical orders within the excurrent canal system were lower in our simulations than predicted based on calculations from a unidirectional strictly hierarchical model of flow for sponges. Flow velocities ranged from ~ 0.02 mm/s to ~ 0.1 mm/s over the entire range of canal segment sizes. Only within the osculum the flow accelerates to a maximum outflow velocity between 0.7 mm/s to 1.1 mm/s. The slow increase in flow velocity within the excurrent canal system differ from previous observations in other sponges, e.g. Haliclona species which reported much higher and faster increasing flow velocities towards the osculum. In case of juvenile S. lacustris this is a consequence of the aquiferous system architecture which displays a compensating increase in available canal volume.
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