Summary
Physical Description
Ecology
Life History & Behaviour
Reproduction
Experiment: Cell Aggregation
Nutrition
Anatomy & Physiology
Evolution & Systematics
Biogeographic Distribution
Conservation & Threats
References & Links |
EXPERIMENT: Cell Aggregation
The experiment was conducted at the Heron Island Research Station, where the Haliclona/Ceratodictyon association was found on the North Beach of the island in the southern Great Barrier Reef.
The experiment aimed to separate the sponge cells from its algal partner and to observer their behaviour once disassociated.
Branches of Haliclona/Ceratodictyon were cut into small pieces (~5mm) and then they were put into a 1l beaker that  was filled with 50ml of sea water. 5ml of sigma Trypsin EDTA was added in order to dislodge cells from their culture surface. After 45 min on the shaker, the algae parts were examined. Due to the fact that there was still a lot of sponge tissue attached on the alga, the pieces were put into a tube that was filled with 0.125 g of Sodium dodecyl sulfate (SDS) and 25 ml of sea water. After 30 min on the shaker the pieces were washed with sea water three times.
The pieces were pushed through a fine mesh at the end of a syringe into a bowl of sea water. This broke the animal down to its individual cells.
Single ramuli (~1.5cm) were removed from the remaining pieces in the syringe and put into Petri dishes with 6mm sea water. The sponge cells were added.
Photo: Ceratodictyon spongiosum without surrounding sponge cells after Trypsin/SDS/Mesh treatment. (Photo: Ronja Schmidt)
In order to compare the potential reaggregation behaviour of the sponge cells, some of the cells were put together in a Petri dish with another species of alga, Gracilaria. Additionally, three Petri dishes with sponge cells and both algae species were set up. Gracilaria was treated in the same manner with Trypsin and SDS as the Haliclona/Ceratodictyon association before added to the dishes to ensure that the same surface alterations were undertaken as on Ceratodictyon spongiosum.
12 Petri dishes, filled with sea water and sponge cells. Differences: Ceratodictyon spongiosum and Gracilaria (upperleft row); Ceratodictyon spongiosum only (upper right row); Gracilaria only (lower right row). (Photo: RonjaSchmidt)
After 3 hours the sponge cells were not observed reaggregating around their algal partner let alone the other algal form. It cannot be said whether they would have done after a longer period of time, whether the treatment with the SDS prevented the sponge cells from recognizing their partner or if they are unable to reestablish the symbiosis once they were separated. Nonetheless, a huge amount of clumps were visible in all of the Petri dishes. This shows the sponge’s incredible ability to reorganize and regenerate itself. It is not said, however, that the sponge can survive for a longer period of time without its symbiotic partner.
 
Top: Gracilaria with aggregating sponge cells – no aggregation around the alga visible. Bottom: Ceratodictyon spongiosum with sponge cells – no aggregation around the alga visible. (Photo: Ronja Schmidt)
   
Cell aggregation after the cells have settled on the ground of the petri dish under dissecting microscope. One hour intervals (top left: first picture; bottom left: last picture). (Photo: Ronja Schmidt) |
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