ScienceAsia 32 Supplement 1 (2006): 057-062 |doi: 10.2306/scienceasia1513-1874.2006.32(s1).057

Biomechanical Properties of Coenocytic Algae (Chlorophyta, Caulerpales)

Robert DeWreede^*

 
ABSTRACT: Coenocytic algae are highly visible components of the seaweed flora in shallow tropical coral and sedimented habitats. Coenocytes are unicellular (acellular) and are able to seal and repair damage to their enclosing membrane, and to possibly regrow lost tissue. There is no documented in situ evidence that entire individuals of coenocytic algae are capable of re-attachment once dislodged. These properties suggest that if these organisms are subjected to sufficient physical stress (e.g. hydrodynamic forces), they will break rather than be dislodged from the substratum. Investigation of some biomechanical properties (force to remove, force to break, and strength) of species of Udotea, Halimeda, and Penicillus shows, however, that in more than 95% of cases when these species are so stressed, they detach whole rather than break. This contrasts sharply with the response of most multicellular algae tested, which frequently break within the thallus. Chemical/structural properties of coenocytes that may contribute to these results are the biochemical nature of the cell walls of coenocytes and the presence of a surface layer of calcium carbonate. The potentially rare occurrence of sufficient hydrodynamic forces to dislodge these algae, and the possibly fatal consequences if herbivory damages the thallus, may result in selection for a tough thallus rather than one that breaks.

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Department of Botany, Faculty of Science, The University of British Columbia, Vancouver, B.C., Canada V6T1Z4.

* Corresponding author, E-mail: dewreede@interchange.ubc.ca