An Evaluation of Fenitrothion Toxicity in Four Life Stages of Rainbow Trout, Salmo gairdneri

Abstract

Lethal and sublethal effects of fenitrothion, an organophosphate insecticide, were investigated in rainbow trout (Salmo gairdneri) embryos, sac fry, fingerlings, and adults. Embryos first exhibited cholinesterase activity 14 days before hatch. Embryos and sac fry at various ages subjected to 34 mg/litre fenitrothion for 24 h under static exposure conditions first exhibited mortality 6 days after hatch. A 24-h lethal concentration of 50 percent of organisms (LC50) of 3.4 mg/litre and a 96-h LC50 of 2.0 mg/litre were obtained using fingerlings exposed to fenitrothion in a flow-through system. Fingerlings surviving 96 h of exposure exhibited cholinesterase activities ranging from 13 to 25 percent of controls (brain) and 30 to 51 percent (skeletal muscle). Adult trout were monitored for electrocardiogram and respiratory responses to fenitrothion concentrations of 5.0, 1.0, and 0.5 mg/litre. At 5 mg/litre, heart rate decreased initially but recovered within 24 h. Cough frequency was directly related to fenitrothion concentration. Based on acute mortality tests, the embryological life stage was the least sensitive, the sac fry stage was intermediate, and the life stages of fingerlings and adults were the most sensitive. The sublethal responses, cholinesterase inhibition in fingerlings and the cough response in adult trout, were sensitive to 0.75 and 0.5 mg/litre fenitrothion.

Use of Respiratory-Cardiovascular Responses of Rainbow Trout (Oncorhynchus Mykiss) in Identifying Acute Toxicity Syndromes in Fish: Part 4. Central Nervous System Seizure Agents

“…In fish, lethal aqueous exposures to AChE inhibitors do not consistently increase fc, which suggests that some other mechanism is responsible for coughing [38]. In fish, lethal aqueous exposures to AChE inhibitors do not consistently increase fc, which suggests that some other mechanism is responsible for coughing [38].…”

Effects of Pollution on Fish

“…Acetylcholine is a neurotransmitter and is thus essential for normal neural functioning of sensory, integrative and muscular systems. In fish, inhibition of the enzyme affects, for example, respiration, feeding and swimming (Wildish & Lister 1973;Post & Leisure, 1974;Klaverkamp et al, 1977).…”

Use of respiratory‐cardiovascular responses of rainbow trout (Oncorhynchus mykiss) in identifying acute toxicity syndromes in fish: Part 4. Central nervous system seizure agents

“…Increased fc in chlorpyrifos-intoxicated trout was probably due to an effect unrelated to the primary mechanism of AChE inhibition. In fish, lethal aqueous exposures to AChE inhibitors do not consistently increase fc, which suggests that some other mechanism is responsible for coughing [38]. Klaverkamp et al [38] reported that fenitrothion (0,O-dimethyl 0-(4-nitro-m-tolyl) phosphorothioate) increased coughing in rainbow trout, whereas acephate (0, S-dimethyl acetylphosphoramidothioate) did not.…”