Mastocarpus Life History
Mastocarpus shows a life history that is interesting even among the other red algae. It has the basic triphasic life history with a tetrasporophyte, gametophytes and carposporophyte, but the variation on this plan gives Mastocarpus some interesting ecological characteristics.
Quadramorphism makes Mastocarpus unique. Each stage in the life history is different, from a crustose tetrasporophyte to the foliose gametophytes to the carposporophyte. In addition, the male and female gametophytes do not even resemble each other (link to morphology.)
A taxonomic characteristic in red algae is how tetraspore production occurs. In Mastocarpus, tetraspore division is cruciate and occurs in tetrasporangia 10 to 15 cells below the cuticle (see tetrasporangia.)
Up into the 1970s, Mastocarpus' tetrasporophyte was thought to represent the separate genus Petrocelis. No sexual life history had yet been identified for Petrocelis though. Cultures of Mastocarpus carpospores revealed that the two genera are separate phases of a single taxon.
Female gametophytes of Mastocarpus can carry out direct development from unfertilized female gametes. This is known as apogamy. Populations of Mastocarpus have been found based almost entirely on this apomictic life cycle. Cultures of what appear to be carpospores grow directly into female gametophytes (link to ecology and natural history.)
Mastocarpus pages copyright W. Ludington 1999