Marine Biology @ UKZN

During our trips to Cape Vidal we always come across very high densities of the acoel flatworm, Convoluta sp. They are always visible around low tide, always at the same place near the effluent line.

There is a clear indication of groundwater seeping through the beachface, and it is possible that there is an N source that they can utilise. Some of the literature suggests that they are "born" without the symbionts (some sources say this is a species of Platymonas, others Tetraselmis), being able to feed as heterothrophs. Then they somehow acquire the algal cells, and loose their ability to feed heterotrophically. As adults they are completely autotrophic (if that term can be used for animals!). They do not migrate up and down the shore with the tide, but possibly move down deeper into the sediment during the rising tide. They are strongly gregarious and congregate at very high densities in bright light, suggesting that they have an interesting photophysiology. That they manufacture DMSP (noticeable as DMS which can clearly be smelled even out in the open) suggests that they have an interesting physiological mechanism to deal with excess free radicals produced under potentially photo-damaging light intensities. A scan of their pigment absorption spectrum shows that they absorb UV light, thereby possibly minimising risks associated with the this waveband of light.