Clast Assimilation and Substrate Attachment in Acropora millipora

Full description

These videos were produced during the development of Brett Lewis' Masters (Research) thesis, 'Clast Assimilation and Substrate Attachment in Acropora millipora' and are listed in the appendices. 

The following is a summary to help infer the behaviours and responses present in the videos. 

Time lapse of A. millipora’s initial response to sediment intrusion and subsequent substrate interaction. During the initial response tissue damage and lesion formation, loose debris and tissue inflammation, slight non-normal discolouration (pink), and significant mesenterial filament activity were all present. Opaque mucous shield formed surrounding the lesion and tissues in contact with the substrate. The tissues begin to anchor to the substrate, sealing the contact area from the surrounding environment.

Time lapse video of the mesenterial filaments of A. millipora accessing the environment surrounding the contact area. To achieve this, the mesenterial filaments employed a twisting motion, similar to a ‘corkscrew’, to move around inside the corallum through the temporary holes or ‘cinclides’ that opened up in the surface body wall, and into the surrounding environment. The timing between the mesenterial’s and the cinclides opening varied with cases mesenterial’s building up in areas until the cinclide opened giving the mesenterial filament access to the surrounding environment. 

Time lapse video of the mesenterial filaments of A. millipora immediately accessing the environment surrounding the lesion and substrate/coral contact area.

Time lapse video of the mesenterial filaments of A. millipora forming a concentrated ball of mesenterial filaments in response to loose skeletal debris.

Fluorescence time lapse video of the thickened mucus shield that A. millipora formed during substrate interaction and lesion formation. The shield acted as a colonising substrate for varying species of ciliates.

Time lapse video of A. millipora showing the coral tissues response to substrate interaction from 1 to 7 days. The coral surface body wall swells at the contact area between it and the ceramic clast. The tissue goes on to form a ridged proto-lappet that, via pulsing, reaches out and superficially anchors the coral to the substrate surface.

Time lapse video of A. millipora indicating a systematic pulsing of the tissues at the edge of the substrate/tissue contact area. The pulsing was followed by the attachment of the proto-lappet structure.

Time lapse video of A. millipora undertaking systematic autolysis of the tissues directly underneath the clast intrusion (12 hours). Tissues were removed by systematic employment of digestive mesenterial filaments in concentrated balls to areas selected for tissue removal. After autolysis the issues become retracted in areas forming a circular hole where the surface tissues were once present.

Time lapse video of A. millipora’s lappet employing undulated pulsing in an attempt to migrate and encrust along the substrate surface. 

Time lapse video of A. millipora’s lappet migration over 5 days and the subsequent encrustation and costae formation. Costae formed in the lappet chamber and appear as irregular lines that run perpendicular to the encrusting edge, in some cases interweaving with each other.