Copper toxicity to the ghost rams-horn snail Biomphalaria havanensis

Authors: MISCHKE,, CHARLES - Mississippi State University; Richardson, Brad; TIWARI,, AMBIKA - Mississippi State University; GRIFFIN,, MATT - Mississippi State University; WISE,, DAVID - Mississippi State University; REHMAN,, JUNAID - University Of Mississippi; ASHFAQ,, MOHAMMAD - University Of Mississippi; NANAYAKKARA,, P. DHAMMIKA - University Of Mississippi; KHAN,, IKHLAS - University Of Mississippi

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2022
Publication Date: 12/2/2022
Citation: Mischke, C.C., Richardson, B.M., Tiwari, A., Griffin, M.J., Wise, D.J., Rehman, J.U., Ashfaq, M.K., Nanayakkara, P., Khan, I.A. 2022. Copper toxicity to the ghost rams-horn snail Biomphalaria havanensis. North American Journal of Aquaculture. https://doi.org/10.1002/naaq.10279.
DOI: https://doi.org/10.1002/naaq.10279

Interpretive Summary: Bolbophorus damnificus is an important parasite in the U.S. catfish industry that uses birds, snails, and catfish throughout its life cycle. Most of these bird hosts are federally protected and there are currently no approved treatments for parasites in food fish, which means control of the snail host is the best management strategy. In this study, USDA-ARS scientists, in collaboration with scientists from Mississippi State University, evaluated the effects of repeated low-dose copper sulfate treatments on two known hosts of this parasite: the Marsh Rams-horn Snail and the Ghost Rams-horn Snail. Adults of both snail species showed similar levels of susceptibility to the treatments well below the accepted range considered safe for fish. While the susceptible ranges for eggs and juveniles of each species varied, these ranges were still below the accepted "safe" range. The study suggests that multiple low-dose treatments could be an effective strategy for managing hosts of the B. damnificus parasite, but that treatments may need to be adjusted depending on whether the farmer is targeting adults, juveniles, or eggs of the snails.

Technical Abstract: Avian piscivores cause direct economic losses to the aquaculture industry through predation, as well as indirect losses through transmission of digenetic trematodes. Bolbophorus damnificus is a trematode parasite associated with significant losses in catfish aquaculture. The complex life cycle involves the American white pelican Pelecanus erythrorhynchos, planorbid snails, and ictalurid catfish. With no approved therapeutics for B. damnificus in catfish Ictalurus spp. and federal protections on American white pelican, management is restricted to controlling snail hosts. Two snail species, marsh rams-horn snail Planorbella trivolvis and ghost rams-horn snail Biomphalaria havanensis, are common inhabitants of commercial catfish ponds and known to transmit B. damnificus. Previous work evaluated copper sulfate toxicity on marsh rams-horn snails; however, data are lacking for ghost rams-horn snails. Herein, laboratory-reared adults of ghost rams-horn snails and marsh rams-horn snails were exposed to copper concentrations ranging from 0.16 to 3.38'mg/L Cu to evaluate 24-, 48-, and 72-h acute toxicity. Additionally, sequential low-dose treatments ranging from 0.1 to 0.8'mg/L Cu were evaluated on eggs, juveniles, and adults of ghost rams-horn snails as a potentially safer treatment regime for ponds. Acute toxicity was similar between snail species for all exposure times. A 72-h exposure produced an LC50 of 0.10 and 0.37'mg/L Cu for ghost rams-horn snails and marsh rams-horn snails, respectively. The LC50 values increased to 1.1'mg/L Cu for both species with 48-h exposure. However, in the multiple low-dose study, a single dose of 0.4 or 0.8'mg/L Cu was lethal to all adult snails after 1'week, as was 0.2'mg/L Cu after two doses. Four doses of 0.1'mg/L Cu or greater killed all ghost rams-horn snail juveniles. Results indicate that marsh rams-horn snails and ghost rams-horn snails have similar sensitivity to copper, and multiple low-dose treatments were effective against all life stages of ghost rams-horn snails. These data indicate that copper can be an effective treatment for snail control in commercial catfish ponds.