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

Abstract

The respiratory-cardiovascular responses of spinally transected rainbow trout to acutely lethal concentrations of chlorpyrifos, cypermethrin, fenvalerate, endosulfan, endrin, and strychnine were examined. Common to all six toxicants, the most striking change in respiratory-cardiovascular parameters was an increased cough frequency. Ventilation frequency and volume dropped in strychnine-exposed trout, but both remained near predose levels (frequency) or elevated (volume) in the pyrethroid-and cyclodiene-exposed trout. In chlorpyrifos-intoxicated trout, ventilation frequency decreased while volume increased. Oxygen consumption remained near predose levels in the chlorpyrifos-, pyrethroid-, and strychnine-exposed trout, but increased dramatically in the cyclodiene-exposed trout. Arterial oxygen, carbon dioxide, and pH declined in all the toxicant groups. In the pyrethroid-and strychnine-exposed trout, hematocrit and hemoglobin levels tended to increase or remain constant during intoxication. Conversely, in the chlorpyrifos-and cyclodiene-exposed trout, values for these parameters decreased. The responses for these pesticides (N = 23 fish) were combined with five fish acute toxicity syndromes (FATS) (A'= 52 fish) previously described (nonpolar narcosis syndrome, polar narcosis syndrome, acetylcholinesterase inhibitor syndrome, respiratory uncoupler syndrome, and respiratory irritant syndrome) and assessed using discriminant function analyses. The final analysis resulted in 93% correct classification of the trout.

Effects of Harmful Algal Blooms on Fish: Insights from Prymnesium parvum

“…The ventilatory volume is an effect of both decreasing oxygen uptake efficiency and an increased MO 2 , both acting together to create a requirement for a larger amount of water passing over the gills [18][19][20]57]. When the gills become increasingly insufficient, the positive trends in MO 2 , Vf, and coughing frequency (Cf) have negative trends, as the fish can no longer sustain a high metabolism due to the deterioration of the gills.…”

“…The frequency was established by timing the duration of 10 ventilatory movements in seconds and dividing that time by 10 to obtain the frequency in hertz (Hz). Instead of using the ventilatory volume (L) used in the FATS approach [18][19][20], the ventilatory frequency per hour was used to calculate a proxy, per breath oxygen uptake (mgO 2 ·kg −1 ) (R), by dividing MO 2 (mgO 2 ·kg −1 ·h −1 ) by the frequency (h −1 ):…”

“…The initial phase of P. parvum toxicity has been reported to be reversible, as damaged gill was observed to be repaired within hours of P. parvum removal [7]. Acute toxicity of different substances to fish has been studied in the context of fish acute toxicity syndrome (FATS), where cardiorespiratory responses of fish were used to distinguish the modes of action of a substance [18][19][20]. The FATS approach determines whether a fish is experiencing gill irritation and damage, and determines the type of the effect, e.g., narcotics, that leads to anesthesia in the fish.…”

“…The FATS approach determines whether a fish is experiencing gill irritation and damage, and determines the type of the effect, e.g., narcotics, that leads to anesthesia in the fish. However, the FATS method is immensely invasive to the fish, requiring a level of instrumentation [18][19][20] that is time-consuming and a high degree of technical skill. Notably, the level of technical skill influences the physiological measurements [21].…”

“…Initial measurements for separating gill irritants, indicative of coughing and ventilatory decoupling, from other toxicants, where ventilatory volume is theoretically associated with oxygen consumption, can be measured by observing the fish. These cough and ventilation rate measurements [18][19][20], together with total animal oxygen consumption (MO 2 ) [22][23][24], it is hypothesized that determining whether the mode of action of an HAB is caused by gill damage or occlusion, or by something else, is possible.…”