Biological Characteristics Of Three Bangia Atropurpurea And The Shape Formation Of Porphyra Crispata

Bangia and Porphyra belong to the Bangiaceae which are the most old and original groups in the Rhodophyta. Bangia and Porphyra are important economic marine algae,and their simple morphology, reproduction and life history had been studied by many algologists. For deep understanding the biological characteristics of Bangia and Porphyra, this study was focused on the cytological observation and molecular biological comparison of three Bangia atropurpurea, and the shape formation of Porphyra crispata was also studied.B. atropurpurea has been poorly studied in China. To understand the basic biological characteristics of B. atropurpurea in China, the morphological, reproduction,chromosomes characteristics and pigment contents of B. atropurpurea were studied in this research. Three B. atropurpurea samples were collected from Niangziguan(Shanxi province), Wuquanshan(Gansu province) and Xinglongshan(Gansu province). The growth environment conditions of the Bangia samples were studied in the fields. The morphological and reproduction characteristics of these three samples were examed under the light microscope. The freshwater Bangia populations in these three different locations were found adhere to rocks, waterfall and fast flowing streams, and the Bangia populations often found coexit with Cladophora insignis. These Bangia samples were unbranched filaments and the length were ranged from 1.1 cm to 3.5 cm.Phycobiliprotein contents of three samples were ranged from 7.26 to 9.46 mg/g, in which the sample from Niangziguan contained the highest concentration, followed by the sample from Wuquanshan. The Xinlongshan sample contained the lowest phycobiliprotein contents concentration in comparison with other samples. These Bangia samples reproduced asexually and the released archeospores germinated into gametophytes continuously. The nuclear division of three Bangia samples were mitosisand the sister chromosomes always assembled as a “8” or a “X” shape in the early metaphase. All freshwater samples had the consistent somatic chromosome numbers of n=4. The length of chromosomes were ranged from 0.42 to 1.67 μm and one of the chromosomes was usually found to be shorter than the other three. This is the first time that the biology characteristics of Bangia samples from Wuquanshan and Xinglongshan have been systematically studied in China, that provides extremely valuable information for the B. atropurpurea research.The rbc L and 18 S r DNA genes of B. atropurpurea samples were collected from Niangziguan(Shanxi province), Wuquanshan(Gansu province), Xinglongshan(Gansu province) and B. fuscopurpurea from Haimen(Jiangsu province), Nanjidao(Zhejiang province) were amplified and sequenced in the present study. The results shows that A+T base contents of rbc L and 18 S r DNA gene sequences were 61.6% and 52.1%,respectively, which were significantly higher than G+C base contents. The rbc L fragments of five populations were 1455 bp in length and the gene mutation rate were14.09%. The 18 S r DNA fragments of five species were 1780 bp with 11.85% gene mutation rate. So the rbc L gene sequences have more variations than 18 S r DNA gene sequences. The analysis of rbc L gene sequence showed that Bangia and Porphyra clustered into two independent branches, the three freshwater Bangia samples were clustered with freshwater samples from other places in the world(100% support). These results indicated freshwater samples were greatly distinct from marine ones. The18 S r DNA gene sequence analysis results showed that, the genetic distance between freshwater and marine Bangia(0.118~0.122) was greater than the genetic distance between Bangia and Porphyra(0.066~0.117), and marine Bangia and Porphyra belong to another branch, which were different from the result of classical classification. According to the Bangiaceae in the newly revised international classification, the marine samples of Bangia were clustered in “Bangia” 2, and the three freshwater samples were clustered in Bangia.The effects of temperature(15℃, 20℃, 25℃, 28℃) on the conchospore germination, the shape formation and reproductive characteristics of different stages in the life history of Porphyra crispate were assessed. The results indicate that both 20℃and 25 ℃were the optimum temperature for the conchospore germination of P. crispate and the highest rate of conchospore germination was achieved at 20℃. The trackingstudy of the chromatophore chimeras shows that meiosis occurred during the stage of conchospore germination and the development of conchospore germination followed a linear pattern. Several factors were found to have impacts on the shape formation of P.crispate: the length width ratios of thalluses became smaller when more longitudinal divisions were identified than the transverse divisions of thallus cells and hence those thalluses were found to be fan-shaped or arc-shaped forms; Typical stellate chromatophore and the segments which formed by germinated cells in the rhizoids also accelerated thalluses to form flower shape. Although sexual reproduction was suggested as the typical reproductive characteristics of P. crispata, some young thalluses could release spores asexually and develop thallus at 15℃ and 20℃. This research provided valuable information on the morphological development and the artifical cultivation technology of P. crispata.