Factors affecting sporulation of Gracilaria cornea (Gracilariales, Rhodophyta) carposporophytes from Yucatan, Mexico

Abstract

Carpospore shedding was studied in Gracilaria cornea in order to determine maximum spore output potential for mariculture purposes. The combined effects of temperature (23, 26 and 29 °C), daylength (8:16, 12:12 and 16:8 light:dark), photon irradiance (darkness, 20 and 40 μmol m-2 s-1) and spore release method (spontaneous release, osmotic shock and drying) were tested. Maximum spore shedding in cystocarpic G. cornea occurred within the first three days depending on temperature. A reduction in spore release periodicity was more evident at 29 °C. Carpospore shedding was mainly affected by temperature and daylength. A higher number of carpospores was released per cystocarp at 26 °C than at 23 or 29 °C. Short day conditions (8:16 L:D) produced a higher number of carpospores at 26 °C, even at the lowest irradiances tested (darkness and 20 μmol m-2 s-1). A combination of 26 °C and short days (8:16) gave the highest carpospore discharge per cystocarp. There was no significant difference between the spore release methods. These results could be applied to promote the establishment of extensive cultivation of G. cornea from spores as an alternative to vegetative propagation in Yucatan coast.