Studies On Physiology And Ecology Of Costaria Costata (C. Agardh) Saunders

Costaria costata (C. Agardh) Saunders is an annual brown macroalgae, which distributes in the north Pacific area, including the Alaska to Califonia, Okhotsk and Great Peter bay of Russian, northeast of Korean peninsula, and north Japan. Recellently, the trial of introduction and cultivation were conducted in Dalian of China. The cultivation of the seaweed will be important to seaweed industry. Costaria costata were used as feeder for abalone, sea urchin etc, in addition, potential material for sea forest plantation.Here in our study, development of gametophytes and juvenile sporophytes of C.costata were studied, effects of different irradiance and temperature on its growth and development were analyzed. Under light microscope, we discovered that within 1 h, zoospores released from sporangium could develop into embryo-spores and then geminate and develop into gametophytic primary cell in the following 2 d. At 10±1°C/60μmol m-2s-1and 12:12 h (L: D) photoperiod, vegetative growth of gametophytes lasted for 6-8 d, and female gametophytes remained unicell and increased to 3-4 times in diameter, while male gametophytes divided into 4-10 cells with slightly increase in cell size. After 10 d cultivation, female gametophytes developed into oogonium and released eggs, while apical cells of male gametophyts developed into spermatangiums, and one sperm with two lateral flagella in different length was released from each spermatangium. Zygotes were formed after fertilization and geminated immediately without dormancy. The first asymmetric divison of zygote resulted in an apical cell of 20μm and a basal cell of 10μm in diameter. The apical cell divided faster and with the notable increase of cell numbers, a hemispherical meristic tissue of 50-60μm in diameter was formed at the top of juvenile sporophyte, while basal cells divided in a relative low speed and small number of cells. Juvenile sporophyte reached to 0.5-2 mm in length after 15 d cultivation under 10±1°C/60μmol m-2s-1and 12:12 h (L: D) photoperiod.Temperature and irradiance had significant influence on the development of gametophyte, as well as growth of juvenile sporophyte and gametophytic clones. It revealed that 15℃was optimal to gametophytic maturity, and 60μmolm-2s-1 was the optimum irradiance. Being cultivated for 10 d, ratio of fertility gametophytes to unfertility ones under 15℃/60μmolm-2s-1 reached to the 83.1%, while under 25℃/20μmolm-2s-1 the ratio was only 4.2%. Juvenile sporotphytes grew best under 10℃/60μmolm-2s-1 which could reach to 1.94 mm in length after 15 d cultivation. Clones of C.costata gametophytes were profusely branched, which were crushed to 2-3 celled branches with tissue crushing machine and then cultured at different temperature and irradiance. After 13 d culture at 15℃/60μmolm-2s-1, cell numbers increased to 12.4 from the initial of 2.62, the gametophytic clones can not survive at 25℃.Two years'seedling production and cultivation of C.costata were conducted at Rongcheng, Shandong from 2007 to 2008. Seedling ropes were cultured under laboratory conditions and when the seedling reached to 0.5-1.0 cm, the ropes were transferred to raft at sea. Transplantation was conducted when the length of juvenile sporophytes reached to 20 cm. The seaweed grew fast from transplantation to March and it reached to 2.0 m in length, 32.0 cm in width and 2.2 mm in thickness in early April. From April to mid May, the color became darke and the blade changed into thicker. Sporophytes became fertile from mid May to mid June, when sporangial sorus occurred at basal to lateral part of the blade.