Study on the early development of sporelings from carpospores of Gracilaria asiatica Chang et Xia was conducted indoors under controlled culture conditions. Besides normal development of sporelings, a new developmental phenomenon of filamentous frond was observed. It was composed of one or two rows of cells, and took place from the outmost brim of the basal disc. During the early disc stage of germinated carpospores, one or two filamentous fronds formed on about 10% basal discs. Simul-taneously, young fronds began to arch slightly from the centers of single and coalescent discs; lately more filamentous fronds up to 80% appeared on the brims of basal discs. Meanwhile one or more upright fronds protuberated on the basal discs. Generally, filamentous fronds exhibited in self-existence or co-existence forms with normal young sporelings on the same basal disc, and single cell detached from filamentous fronds developed into a new filamentous frond. This new phenomenon exhibited a unique differentiation pathway during the early development of G. asiatica, which would be potential for the ap-plication in artificial sporelings nursery.
In order to find out whether long interspersed elements (LINEs) existed in macro-algae ge- nomes or not, we tested the LINE homologues in representative families (species): Gracilaria (G. eucheumoides Harv., G. tenuistipitata Chang et Xia, and G. textorii (Sur) De-Toni), Laminaria (L. longis- sima Miyabe and L. japonica Aresch.), and Ulva (U. lactuca L. and U. pertusa Kjellm.) during 2004 to 2005. Polymerase Chain Reaction (PCR) was carried out with degenerate oligonucleotide primers de- signed from LINEs of rice homologues and Cin4 of maize. Cloning and nucleotide sequencing of the PCR products revealed that 4 clones that derived from 3 species of Gracilaria have LINE homologues. The nucleotide sequences of the 4 LINE homologues diverged greatly, but the amino acid sequences deduced from them were relatively conserved. The endonuclease regions of the LINE homologues greatly di- verged from that of other plants, but they had closer phylogenetic relationship to Zepp elements in Chlor- ella sp., which indicated that sequence divergence by vertical transmission has been a major influence on the evolution of algal LINEs.
Laminaria gametophyte was greatly influenced by light in its growth and development. Using light-emitting diodes (LED) as blue and red light sources, we analyzed the light effect on gametophytes devel- opment of Laminaria japonica Aresch. The gametophytes were obtained from zoospores collected in April, May, July, 2003 and September, 2004. We found that the growth of gametophytes was stimulated by increasing inten- sity of blue light (BL) and red light (RL) illumination, of which BL was obviously stronger than that of RL. The fertilization of gametophytes depended largely on BL, and only sufficient BL illumination could take the repro- ductive effect. In addition, we noticed that there was a significant difference in light responses for gametophytes developed from zoospore collected in different times. For zoospores released in April, under BL1 (73.90 μmol photons/m·s), the unicellular female gametophytes and multi-cellular male gametophytes produced eggs and sperms respectively, and further developed towards sporophytes. However, for gametophytes developed in May, July or September, they became multi-cellular and never formed oogonia or antheridia. It is believed that the Laminaria sporangium maturation stage could affect the gametophytes reaction to BL under laboratory culture conditions. Therefore, cryptochrome- or phototropin-like BL photoreceptors is probably involved in BL-induced development of Laminaria gametophytes.
Chondrus is an economically important red algae widely used for food and biochemical pur- pose. It early development is crucial for the culture and seedling propagation. We chose tetraspores and car- pospores of Chondrus ocellatus as examples for experiment of the culture, induction and release in laboratory condition, aiming to understand early development of C. ocellatus and to apply in seedling production. Ma- ture C. ocellatus were collected in Qingdao, China, from Nov. to Dec. 2004. After the gametophyte and tet- rasporophyte were brushed and washed with sterilized seawater, the algal materials were treated in 1.5% KI for 20 min, then were dried for 1h to stimulate the releasing of spores. After the spores released overnight, it were cultured in PES medium, incubated at 18 ℃, 10±2 μmol/(m2·s1) in 12:12h (light: dark). The observation and recording under microscope were carried out. Continuous observation of the early development showed that both tetraspore and carpospore are similar to each other. In general, three stages of the early development were shown being division, discoid crust and seedling stages. To the division stage, the most obvious feature was the increasing of cell number; during the discoid crust stage, the discoid crust had a three-dimensional axis, and it began to differentiate into two types of cells: the basal cells and the apical cells; and to the seed- ling stage, several protuberances-like appeared on the discoid crusts and formed juvenile seedlings. Carpo- spores and tetraspores exhibited a similar development process that included division stage, discoid crust stage and seedling stage.
