Galvanized material is a promising approach to control Amyloodinium ocellatum infection in fishes

Abstract

Amyloodinium ocellatum is a worldwide distributed dinoflagellate that infects marine and brackish water fish, causing mass mortality and economic loss. This study evaluated the efficacy of the seawater immersed with galvanized materials (IGM seawater) in controlling A. ocellatum reinfection in susceptible host Trachinotus ovatus. Furthermore, the toxicity of IGM seawater to the dinospores infectivity, tomonts development, and trophonts parasitism was determined in Acanthopagrus latus. The expression of zinc transporters in A. latus gills and livers was also detected after A. latus exposure to IGM seawater. The results revealed that parasite abundances on infected T. ovatus were significantly decreased in the seawater immersed with 0.1 m2/m3 of galvanized iron mesh for 2 days ([0.1–2 d] group) or galvanized iron plates with a 56.25% tank coverage for 1 day ([56.25% - 1 d] group). Besides, the survival rates of the infected T. ovatus in the [0.1–2 d] and [56.25% - 1 d] group were 100% on the 14th-day post-infection, while 0% in the control group. The infectivity of dinospores was significantly inhibited in the seawater immersed with 0.4 m2/m3 of galvanized iron mesh for 2 days ([0.4–2 d] group) by 89.50%. In addition, the reduction of trophonts in the [0.4–2 d] group was 46.24% compared to the control group. However, the hatching rate of tomonts in the seawater immersed with 0.4 m2/m3 of galvanized iron mesh for either 1, 2, or 3 days was 100% at 48th hr post-treatment. At the same time, the zinc ion concentrations in the IGM seawater group were continuously increased. On the contrary, the mRNA levels of zinc transporters ZIP7 and ZIP11 in the liver of A. latus exposure to IGM seawater were significantly down-regulated. Therefore, A. latus acclimatizes to a high‑zinc environment by reducing zinc ions influx to maintain intracellular zinc homeostasis. These results imply that using galvanized material is a promising approach to controlling A. ocellatum infection in fish.