Structural Development of Marine Green Alga (Ulva rigida C. Agardh, 1823) during Cultivation

Ulva rigida C. Agardh (sea lettuce) is a marine green alga. It grows naturally near shorelines in areas with freshwater influence. It can also be cultivated easily on farms and can be developed into many healthy food products, which bring in revenue for Thailand. It is important to develop an effective way to cultivate the alga. In this research, the molecular biology of sea lettuce using the tufA gene for the identification of Ulva genus and morphological characters at different culturing periods of U. rigida thallus were investigated using a light microscope (LM), a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The results revealed that the U. rigida alga consisted of various cell shapes including elliptic, irregular triangle, irregular quadrilateral, pentagonal and polygonal. The cell size increased with increasing periods of culture. However, when the alga was cultured for 28 days, the cell sizes were smaller than the original cells due to cell division during aging, resulting in an increase in cell numbers. U. rigida had grown rapidly in 14 days which was a relatively short period of cultivation. The results of this study indicate that U. rigida has a potential to be scaled up in pilot and commercial scales. HIGHLIGHTS The molecular analysis of sea lettuce from Phetchaburi Coastal Aquaculture Research and Development Center, Sub District: Bang Kaeo, District: Ban Laem at Phetchaburi Province, Thailand was found to be rigida The morphological and anatomical characters of rigida thalli were studied with light microscope, transmission electron microscope and scanning electron microscope techniques The cell sizes of rigida thalli changed with culturing days. They were the largest at 14 days in the surface view, and at 14 and 21 days in the transverse section GRAPHICAL ABSTRACT