Yaowaluk Chitramvong

Ultrastructural changes in the digestive system of Indoplanorbis exustus (Gastropoda: Planorbidae) exposed to the molluscicides, niclosamide and Brassaia actinophylla

Abstract The adult snails, Indoplanorbis exustus were exposed to the synthetic molluscicide, niclosamide, and the crude – aqueous extract of Brassaia actinophylla at the LC50 concentrations (0.009 mg/ 1 and 23.73 mg/1, respectively) for 24 hours. The results showed relatively similar ultrastructural changes in the digestive system of snails exposed to niclosamide and B. actinophylla. The general cytological alterations that occurred in the epithelia of esophagus, intestine and digestive gland were the formation of blebs, increased fusion of vacuoles, infolding and thickening of basal lamina, formation of myelin-like figures, degranulation and dilation of rough endoplasmic reticulum, swelling of mitochondria and cristae, and an increase in mucus production. Most of these reactions were more severe in snails treated with B. actinophylla than those exposed to niclosamide.

Acute toxicity of a plant molluscicide, Brassaia actinophylla on Indoplanorbis exustus and non-target organisms

Abstract A total of 50 different plant species of 22 families was investigated for molluscicidal activity against Indoplanorbis exustus. Twenty-one species (42%) demonstrated molluscicidal activity. The crude water extract of Brassaia actinophylla showed the best result with 24 hr. LC50 and LC90 values of 23.73 and 32.11 mg / l, respectively. The control group of snails exposed to niclosamide showed 24 hr. LC50 and LC90 values of 0.009 and 0.01 mg / l, respectively. The 24 hr. LC50 and LC90 values of the crude water extract of B. actinophylla on two species of fish, namely, Puntius gonionotus and Poecilia reticulata were 47 and 55 mg/1, and 85 and 111 mg/1, respectively. Concerning the crustacea, Moina macrocopa and Macrobrachium rosenbergii, the 24 hr. LC50 and LC90 values of the crude water extract of B. actinophylla were 258 and 861 mg/1, and 141 and 181 mg/1, respectively.