The Zhegu vegetable belongs to the phylum Rhodophyta, order Caulerpales, family Caulerpaceae, and genus Zhegu. It contains the compound Caulerpic acid, which has the ability to expel parasites, and also has a paralyzing effect on the central nervous system. Therefore, it has value as both an anthelmintic and a research tool for the central nervous system.
Historical Origins
Zhegu vegetable has been used in China since ancient times to expel roundworms. The name Zhegu vegetable first appeared in the 1530 Fujian "Zhangpu County Chronicle". "Zhegu vegetable grows in the sea rocks. When crushed, it is dark in color. When children eat it, it can expel worms from their intestines." The "Min Book" and "Compendium of Materia Medica Supplement" also have similar records. Zhegu vegetable is also known as roundworm medicine, black vegetable, and stone scar. It is produced along the coastal areas of Zhejiang, Fujian, and Guangdong provinces in China.
Zhegu vegetable is produced in Zhejiang province, China, south of the Yangtze River. It has also been found in Fujian, Guangdong, and Shanghai. It is a widely distributed subtropical seaweed. In addition to China, it is also found in Japan (Pacific coast from central Honshu to Kyushu, western coast of Kyushu and northern coast, Ryukyu Islands), Malaysia, the Pacific coast (from Costa Rica to Hawaii), Polynesia, Australia, New Zealand, and the warm waters of the Atlantic and Indian Oceans.
Medicinal Properties
Zhegu vegetable is rich in alginic acid, mannuronic acid, crude protein, iodine, and other inorganic salts. Traditional Chinese medicine believes that Zhegu vegetable has a salty and cold nature, and has the effects of clearing heat, detoxifying, softening hard masses, and expelling parasites. It is a good seaweed for both food and medicine, and can be used to treat chronic bronchitis, asthma, and other conditions, especially for expelling roundworms.
Zhegu vegetable can be consumed fresh, or used in dishes such as Zhegu vegetable soup and Zhegu vegetable with meat slices.
Ecological Characteristics
Zhegu vegetable has three generations: the gametophyte, tetrasporophyte, and carposporophyte. The gametophyte is dioecious and similar in appearance, and the carposporophyte parasitizes on the female gametophyte.
Zhegu vegetable has a height of only 1-4 cm and grows in clusters. When fresh, it is dark purple with a hint of green. After drying, it turns black. The thallus is flat and composed of irregularly branched leaflets, 1-2 mm wide. The leaflets have a prominent midrib that extends from the central axis to the apices. Secondary branches or hair-like structures grow at the branching points. The reproductive organs are tetrasporangia and cystocarps. The former are located in the upper part of the branches, while the latter are spherical and mostly located on the inner surface of the midrib or at the branching points.
Zhegu vegetable is mostly found on rocks, breakwaters, and old wooden piles in the mid to high intertidal zones near river mouths in warm temperate zones. It can also grow in areas up to 10-20 kilometers upstream and with a specific gravity of 1.006-1.010. It has a higher density in the north and east coastlines, shaded areas, and places with accumulated mud. Its vertical distribution ranges from above the high tide line to near the highest spring tide line, with a distribution range of up to 2.7 meters. It often grows alongside other seaweeds such as Ulva lactuca and Enteromorpha. The thalli can first be observed in winter, with individual sizes ranging from 0.5-1.3 cm and the largest reaching 1.8 cm. The biomass is highest during the rainy season in the southern region, ranging from 76-130 grams per square meter.
In Shanghai, due to its proximity to the mouth of the Yangtze River, the salinity of seawater ranges from 2% to 12%, resulting in a very limited distribution of large seaweeds. Zhegu vegetable is often found mixed with floating mud, blue-green algae, and filamentous algae on the backlit surface of breakwaters, and can be seen year-round.
Cultivation of Zhegu Vegetable
1. Cultivation methods
Based on the habits and reproductive characteristics of Zhegu vegetable, modern scientific techniques are used for artificial cultivation. It is a valuable medicinal seaweed with development potential.
2. Cultivation process
Zhegu vegetable is still not commercially cultivated due to its small size. However, with the rise of biotechnology, research on Zhegu vegetable has been conducted as follows:
Suspension culture technique: Different tissues of Zhegu vegetable are cut into sections. Both multicellular and single-celled sections have the ability to regenerate into complete plants. Therefore, they can be cultured in high-density suspension. The culture medium should contain nitrogen, phosphorus, and other nutrients, and the seawater should be replaced every 10 days. Harvesting can be done monthly. During harvesting, a portion of the sections can be re-cultured. The size and density of the sections should be appropriate. One harvest is equivalent to the original amount of algae, with a minimum of 50%. This cultivation method allows for multiple harvests from a single algae inoculation, and is more efficient in terms of time and space compared to traditional methods.
Segment sowing technique: Segments can not only be cultured in suspension, but can also be sprinkled on net curtains to produce rhizoids or pseudo roots for secondary attachment and growth into upright seedlings. Alternatively, segments from suspension culture can be taken out and sprinkled on net curtains, where they can quickly attach and grow into complete thalli. This method can replace spore cultivation and achieve faster and better results than spore seedlings.
Protoplast culture technique: Most cells of Zhegu vegetable can be isolated into protoplasts, which can differentiate into creeping parts and grow into Zhegu vegetable with erect branches, some of which also produce tetrasporangia. However, the number of fully grown plants and the optimal cultivation conditions still need further research.
3. Harvesting and processing
For artificially cultivated segments in suspension, they can be harvested by scooping them out with tools and drying them. Naturally grown thalli are generally harvested from March to April each year and sun-dried, or handcrafted into 9 square centimeter vegetable cakes and bundled for sale.
