Life history, growth, and pigment content of two morphological variants of Hypnea pseudomusciformis (Gigartinales, Rhodophyta)

Abstract

Specimens previously described as Hypnea musciformis and Hypnea nigrescens in Brazil were shown to be morphological variants of a new species named Hypnea pseudomusciformis, which has been used for the production of carrageenan on the coast of Brazil. In this study, individuals of both morphological variants were collected in the field and cultivated in unialgal culture conditions. The life history of both variants was completed in 118 days. Tetrasporophytes produced tetrasporangia in 40 days. Released tetraspores germinated and 15 days later, an erect cylindrical axis developed from basal disk. At the age of 35 days, spermatangial conceptacles could be observed, and after 3 days of co-culture of male and female gametophytes, cystocarps could be observed, indicating the occurrence of fertilization. Finally, carpospores were released from cystocarps after 10 days, germinated and originated new tetrasporophytes in 15 days. When cultured, the morphological differences between the “musciformis” and “nigrescens” variants were attenuated and the life histories were the same. Furthermore, both morphological variants had different growth rates, but similar pigment content. These results corroborate that, for Brazil, specimens previously identified as H. musciformis and H. nigrescens are variants of H. pseudomusciformis, a highly plastic species.