Life cycle of Porphyra vietnamensis Tanaka & Pham-Hoang Ho from Thailand

Porphyra vietnamensis Tanaka & Pham-Hoang Ho is a tropical species of high potential for farming. Studies of the life cycle have been conducted for many years but have not been successful until recently. Mature thalli were collected from Songkhla, in the southern part of Thailand, and were used to obtain Conchocelis in the laboratory in Bangkok. Conchocelis in shells as well as free-floating filaments could be observed after one week of incubation at 25 °C, 25 salinity and 350–500 lux light intensity, and covered the culture shell surface within 2 months. Conchosporangia were formed after being incubated for 10 days at 30 °C, 20 salinity under light intensities of 350–500 lux with a photoperiod of 12 hours a day. Induction of conchospore release was achieved by lowering the temperature to 25 °C and the salinity to 10–15 and increasing the light intensity to 800–1000 lux. Liberated conchospores germinated into young thalli which became mature after 70 days.     

Microsatellite markers from expressed sequence tags (ESTs) of seaweeds in differentiating various Gracilaria species

Gracilaria is a red seaweed that has been cultivated worldwide and is commercially used for food, fertilizers, animal fodder, and phycocolloids. However, the high morphological plasticity of seaweeds often leads to the misidentification in the traditional identification of Gracilaria species. Molecular markers are important especially in the correct identification of Gracilaria species with high economic value. Microsatellite markers were developed from the expressed sequence tags of seaweeds deposited at the National Center for Biotechnology Information database and used for differentiating Gracilaria changii collected at various localities and two other Gracilaria species. Out of 33 primer pairs, only one primer pair gave significant results that can distinguish between three different Gracilaria species as well as G. changii from various localities based on the variation in repeated nucleotides. The unweighted pair group method using arithmetic mean dendrogram analysis grouped Gracilaria species into five main clades: (a) G. changii from Batu Besar (Malacca), Sandakan (Sabah), Bintulu (Sarawak), Batu Tengah (Malacca), Gua Tanah (Malacca), Middle Banks (Penang), Sungai (Sg.) Merbok (Kedah), Teluk Pelandok (Negeri Sembilan), Pantai Dickson (Negeri Sembilan), Sg. Kong-Kong (Johore), and Sg. Pulai (Johore); (b) Gracilaria manilaensis from Cebu, Philippines; (c) G. changii from Morib (Selangor); (d) Gracilaria fisheri from Pattani, Thailand; and (e) G. changii from Pantai Dickson (Negeri Sembilan), Gua Tanah (Malacca), Sg. Merbok (Kedah), Sg. Kong-Kong (Johore), and Sg. Pulai (Johore). This result shows that this primer pair was able to distinguish between three different species, which are G. changii from Morib (Malaysia), G. fisheri from Pattani (Thailand), and G. manilaensis from Cebu (Philippines), and also between different genotypes of G. changii. This suggested that the simple sequence repeat primer we developed was suitable for differentiating between different Gracilaria species due to the polymorphisms caused by the variability in the number of tandem repeats.     

Effects of wave exposure on population and reproductive phenology of an algal turf, Gelidium pusillum (Gelidales,Rhodophyta), Songkhla,Thailand

The effect of wave exposure on the population and reproductive phenology of the common red alga, Gelidium pusillum (Stackhouse) Le Jolis, was investigated between July 2003 and June 2004, at Suan Song Tha Le, Songkla Province, Thailand. Lengths of thalli, percentage cover, percentage of reproductive fronds and the number of reproductive structures were examined monthly in relation to different degrees of wave exposure (sheltered vs. exposed), temperature, rainfall, day length and tidal cycles. Frond length and percentage cover of G. pusillum were different among sites and seasons. Shorter fronds were found on the exposed shore which had a greater percentage cover. Fronds bleached and died off during the summer months (April and May), which resulted in shorter fronds and reduced percentage cover in June. The thalli reproduced throughout the year, with a predominance of tetrasporophytes. The highest percentage of tetrasporic fronds was 33% in February 2004 and 13% of cystocarpic fronds in April 2004, but male gametophytic fronds were never observed. Rainfall showed a strongly negative influence on reproduction since no reproductive fronds were observed during the rainy season (R² = 0.49, P = 0.01). The dominance of G. pusillum at this study site and throughout elsewhere in turf habitats might be a function of persistent vegetative growth, densely clumped, and the ability to reproduce almost throughout the entire year.     

Growth and production of Thai agarophyte cultured in natural pond using the effluent seawater from shrimp culture

Hydrobiologia - Growth rate determinations of the Thai agarophytes, Gracilaria fisheri (Xia et Abbott) Abbott, Zhang et Xia and G. tenuistipitata Chang et Xia var. liui Chang et Xia, were conducted...