Screening the Efficacy and Safety of Molluscicides from Three Leaf Extracts of Chimonanthus against the Invasive Apple Snail, Pomacea canaliculata

Abstract

Pomacea canaliculata, the invasive snail, is a host of the parasitic nematode Angiostrongylus cantonensis, which has adverse effects on the agriculture system and human health. This work evaluated the molluscicidal activity of petroleum ether extracts (PEEs) from three species of Chimonanthus against the snail P. canaliculate. Pcp (PEE of C. praecox) showed the most effective molluscicide activity. Sixty-one compounds were identified by GC-MS and the main components were terpenoids and fatty acids. The half-lethal concentration (LC₅₀) of Pcp at 24 h (0.27 mg/mL) and 48 h (0.19 mg/mL) was used to evaluate the biochemical alterations in snail tissue. These sublethal concentrations caused the levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activity to increase, while acetylcholinesterase (AChE) activity decreased. Also, under LC₅₀ treatment, several histological changes were observed in the hepatopancreas and foot of the snail compared with the control group. Moreover, the toxic test in rice demonstrated that Pcp has low toxicity. These results suggest that Pcp could be developed as an effective molluscicide for P. canaliculata control.

Keywords: Chimonanthus; Pomacea canaliculata; biochemical analysis; histopathological alterations; molluscicidal activity; toxicity.

Figure 1

Distribution of common and unique components. Amounts of PEE chemical compounds illustrated by Venn diagram (A). Percentage stacked plot (B) of common compounds from three samples.

Figure 2

Molluscicidal activity of Pcs (A), Pcz (B), and Pcp (C) against P. canaliculata. Significance between the mean of each group is compared at the p < 0.05 level (n = 3).

Figure 3

Light micrograph of the foot of P. canaliculata stained with hematoxylin and eosin staining (HE). A1 (×100) and A2 (×400) are the blank control; A3 (×100) is the negative control; A4 (×100) is the treated group. ec: epithelium cell; pc: pigment cell; mf: muscle fiber; lv: lipid vacuole.

Figure 4

Light micrograph of the hepatopancreas of P. canaliculata stained with hematoxylin and eosin staining (HE). B1 (×100) and B2 (×400) are the blank control; B3 (×100) and B4 (×400) are the negative control; B5 (×100) and B6 (×400) are the treated group. bc: basophilic cell; dc: digestive cell; dv: digestive vacuole; bp: black particle; bm: basal membrane; ct: connective tissue; tl: tubule lumen.

Figure 5

Hepatopancreas surface of P. canaliculate, observed by scanning electron microscopy. C1 (×300) and C2 (×1000) are the blank control; C3 (×300) and C4 (×1000) are the negative control; C5 (×300) and C6 (×1000) are the treated group.

Figure 5

Hepatopancreas surface of P. canaliculate, observed by scanning electron microscopy. C1 (×300) and C2 (×1000) are the blank control; C3 (×300) and C4 (×1000) are the negative control; C5 (×300) and C6 (×1000) are the treated group.

Figure 6

The enzyme activities in P. canaliculata snails exposed to LC₅₀ of Pcp after 24 and 48 h. Values represent the mean ± SE (n = 3). ALP activity (A); ALT activity (B); AST activity (C); AChE activity (D). Bars marked with different letters indicate a significant difference based on the Waller–Duncan test at p < 0.05.

Figure 7

Effect of Pcp addition (A) on biomass production (B), growth in the shoots (C), and relative chlorophyll content in the rice leaves of rice plants (D) (n = 6) after 5 days of treatment. Bars marked with the same letter for each group do not differ significantly according to the Waller–Duncan test at p < 0.05.

Figure 7

Effect of Pcp addition (A) on biomass production (B), growth in the shoots (C), and relative chlorophyll content in the rice leaves of rice plants (D) (n = 6) after 5 days of treatment. Bars marked with the same letter for each group do not differ significantly according to the Waller–Duncan test at p < 0.05.