Aclimatação da macroalga vermelha Gracilaria birdiae (PLASTINO & OLIVEIRA) em condições laboratoriais visando a esporulação e o desenvolvimento de tecnologias de cultivo

Abstract

The red marine macroalgae Gracilaria birdiae, described by Oliveira and Plastino, is a species present in Brazilian tropical waters, from the coast of Ceará to the State of Espírito Santo. It has great commercial interest, mainly in the market of thickeners and gelling agents (agar), due to the high value of this phycocolloid. The aim of this work was to establish the acclimatization and adaptation of the red seaweed G. birdiae under laboratory conditions, as well as to foster the release, germination and spore fixation in inert support for in vitro macroalgae cultivation. Therefore, the macroalgae adaptation test was carried out in different culture means. Female gametophyte seedlings with mature cystocarps, which were stored in flasks, released carpospores in PM means, which were maintained at 36 ± 1 salinity, 28 ± 2 ° C, photoperiod 14:10 h (dark light), irradiance of 12 ± 5 μmol of photons m-2 s-1, supplied by blue LED lamp. The carpospores that were coalescing were submitted to cavitation technique. The germination of tetraspores of G. birdiae in situ was also monitored and a biweekly measurement of developing stems was performed. Subsequently, tests were carried out to fix the carpospores on cotton, polyethylene and polypropylene ropes, where mini-frames were left in contact with 5 cm female gametophyte stalks containing 5 mature cystocarps / thallus. In the first week, there was no change in the means, only supplementation with MP and salinity adjustment. After six weeks of culture, the G. birdiae was adapted to the means tested, where the chosen medium was sea water + VS. The irradiance applied during the whole experiment (12 μmol of photons m-2 s -1 ± 2) was favorable to the growth and acclimatization of the seedlings. After 30 days of cultivation, the carpospores were in the stage of standing stems (approximately 20 μm) and were submitted to cavitation, obtaining a positive effect on the separation, which did not occur effectively with carpospores of 120 days of cultivation. The measurements performed with 15, 45 and 60 days of gametophytic stems showed a linear growth with average values of length of 121.8μm, 567.6 μm and 806.2 respectively. As the days passed, some gametophytic thallus detached from the mother plant and reached an average length of 0.2 cm in 37 days of cultivation. During the carpospores fixation process in the mini-frames, it was reported a greater fixation in the cotton ropes than in the polyethylene ropes. In the polypropylene ropes, after 15 days a light red pigmentation layer was observed on the mini-frames. After 35 days of incubation, a thicker layer was observed by naked eye, due to the formation of seedlings. These seedlings measured approximately 100μm and 240μm after 28 and 35 days, respectively. Considering the above, we can state that the fixation and germination of G. birdiae carpospores in the laboratory becomes a biotechnological tool applicable to the development of macroalgalmariculture in the northeast of the country.