TOXICITY OF RICINUS COMMUNIS SEED EXTRACT AND ITS MECHANISM ON POMACEA CANALICULATA

Biological invasion refers to the process that organisms invade into another new environment through natural or man-made way from the original habitat, causing economic losses or ecological disasters to biodiversity, agriculture, forestry, animal husbandry and fishery production and human health. Human activities and the development of global integration accelerate the occurrence of biological invasion, which poses a serious threat to the global biodiversity and economy. Since entering the 21st century, biological invasion has continued. Pomacea canaliculata Lam, native to the Amazon River Basin of South America, was introduced into southern China as an aquatic economic animal in the 1980s because of its rich protein content and high nutrient content. Later, it was abandoned in the fields due to excessive blind breeding, too strong fishy smell and poor taste, and spread to the aquatic environment such as rice fields through canals and rivers. Because of its strong fecundity, adaptability and stress resistance, miscellaneous food habits and lack of natural enemies, the snail has become a disaster in many areas of southern China, which poses a major threat to the biodiversity, ecosystem, crops and aquatic plants in the invaded areas. In addition, Pomacea canaliculata is the intermediate host of Angiostrongylus cantonensis, which causes eosinophilic meningitis, and has indirect potential harm to human health. In 2000, the IUCN Expert Committee on alien invasive species listed Pomacea canaliculata as one of the world’s 100 malignant alien invasive species. In March 2003, the State Environmental Protection Administration listed the first batch of 16 alien species to invade China.　　The control methods of Pomacea canaliculata can be divided into four aspects. First of all, physical methods are used to collect snails and eggs manually. During the peak breeding period, human resources are concentrated to collect snails in fields, canals and other areas. During the spawning period, bamboo chips and wooden sticks are inserted in the rice fields to attract the snails to lay eggs and destroy the collected eggs. However, this method has the characteristics of high frequency spawning, strong sustainability of prevention and control, rapid spread with the current, and it is difficult to control. In addition, the artificial fishing cost is high and the timeliness cannot be met for the large area where the Pomacea snail occurs. The second is chemical control. Though the molluscicides, such as spiromethane, tetraacetaldehyde and copper sulfate, are put in the rice fields, rice fields and channels at the same time. Although the effect is obvious, it is easy to cause serious environmental pollution if it is not used properly, and the snail is easy to produce drug resistance. The secondary biological method is to make use of the thin shell and meat of Fushou snail, which is high in protein, low in fat and has more in the areas where snails occur, ducks, fish and crabs are cultivated. However, in the process of biological control, it is necessary to strictly control the number of biological population to avoid animal feces polluting the water environment and damaging people’s water sanitation. Finally, in order to prevent and control Pomacea canaliculata with camellia seed cake, saponins and other plant sources, it has become a hot spot in the field of snail control due to its long-term, economic and ecological safety to non target cells. However, there are few studies on the extraction and preparation of botanical toxicants and their toxic effects on Pomacea canaliculata.　　The results showed that castor seed was highly toxic, and the main toxic components were ricinine and ricin. Among them, ricin was one of the most toxic plant toxin proteins, which has a strong insecticidal and bactericidal effect. When it entered the animal body, it would be decomposed by the object itself, and it would not accumulate in the biological chain and produce drug resistance. Ricinine is a kind of alkaloid with low toxicity, which can cause vomiting and various toxic reactions. It can lead to liver and kidney damage, convulsion, hypotension and death. At present, there is no report on the toxicity of castor oil extract to Pomacea canaliculata.　　The biological soaking method was used to prepare the botanical toxicant from the extract of Ricinus communis L. seed. The toxic effects of different extract concentrations (0, 0.5, 1.5, 3.0, 4.5, 6.0 g/L) on the snails were studied. The liver tissue physiological and biochemical indexes of the snails treated with sublethal concentrations of 1.58 (LC₂₅), 3.82 (LC₅₀) and 6.05 (LC₇₅) g/L and their correlation were further studied analysis of the mechanism of its toxic action. The results showed that after 48h treatment, the mortality of Pomacea canaliculata increased with the increase of time and concentration, and the mortality of Pomacea canaliculata was significantly different under different concentrations (P<0.05). The protein content (TP), malondialdehyde (MDA) content and catalase (CAT) activity in hepatopancreatic tissue were significantly different from those in the control group after 48h of sublethal concentration treatment. There was a significant negative correlation between catalase (CAT) activity and malondialdehyde (MDA) content (P<0.05). The extract of Ricinus communis L. seed can cause damage of liver tissue and disorder of metabolism by affecting the content of protein (TP), malondialdehyde (MDA) and the activity of catalase (CAT) in the liver tissue, so as to achieve the toxic effect. The results of molluscicidal test and physiological and biochemical indexes showed that castor seed had potential molluscicidal effect on Pomacea canaliculata.