The presence of gigartinine in a New Zealand Gracilaria species

Gigartinine, 5-(3-amidinoureido)-2-aminovaleric acid, serves as a chemotaxo nomic marker to distinguish two species of Gracilaria with very similar mor phologies. Gigartinine was identified by C-13-NMR spectroscopy and amino ac id analysis of a cold-water extract from Gracilaria sp. nov., collected fro m a sheltered harbour locality at Blockhouse Bay, Auckland, New Zealand. Le vels of this amino acid, naturally ca. 5% by dry weight of seaweed, were ab le to be depleted and then restored during a nitrogen pulsing experiment. I n contrast, native and pulsed samples of Gracilaria chilensis from Point Ar thur, Wellington showed no extractable gigartinine. Although these two spec ies are unable to be distinguished in the field by morphological characteri stics, they can be separated by the presence or absence of gigartinine.