Structure, life history and hybridization of atlantic gigartina teedii (Rhodophyta) in culture

The life history in cultured isolates of the marine red alga Gigartina teedii (Roth) Lamour. from the subtidal of the River Yealm, south Devon, England and the intertidal of the Rade de Brest, Brittany, France is described. Plants start to reproduce after about the same time at 20°C, 16: 8 h; 15°C, 16: 8 h and 15°C, 8: T5 h, but the morphology of the plants at the time of reproduction varies according to the regime. Plants grown at 10°C, 16: 8 h do not reproduce, and this may account partially for the observed northern limit of this species in European waters (south-west Britain). In both isolates, several successive, complete life histories have been achieved without any deviation from a Polysiphonia-type life history. Gametangial plants are always dioecious, and tend to reproduce more rapidly when unattached. Gametangial plants of G. teedii from England, France and Brazil are interfertile and fertile tetrasporophytes develop from the resulting carpospores. Gigartina teedii isolates from Brazil show Mendelian inheritance of a non-sex-linked recessive colour variant which has not been observed in the European strains. Attempted crosses with G. acicuiaris (Roth) Lamour. from France and G.johnstonii Dawson from the Gulf of California have proved negative. Details of the structure and reproduction of G. teedii in culture are presented, together with a discussion of the genera of the Gigartinaceae and of the generic status of this species.