Avian Chemical Defense Mechanism - Essay Example

Homobatrachotoxinin is a member of the family of steroidal alkaloids called Batrachotoxinins (Fig 1). These compounds have a molecular formula of C31H42N2O6, with a molar mass of 538.67g/mol and a density of 1.304g/ml. It is highly toxic and the median lethal dose (LD50) is 0.002 to 0.007 mg/kg depending on species to species (Daly, 1965).

The mechanism of its toxicity is related to its action on the voltage-gated sodium channels present in the cell membrane. Since it is a steroidal alkaloid it can easily access the cell membrane of the predators, binds to the voltage-gated sodium channels, and keeps them in a state of depolarization. These compounds bind irreversibly to the sodium channels creating a conformational change in them, that keeps the channels always in an open state. Further, they also reduce the conductance of these channels leading them to be in a state of less excitability. This impacts the nervous system because the membrane cannot become stabilized to its resting level (generation of resting membrane potential is hampered) which leads to impairment of neuromuscular transmission in the predator leading them into a state of paralysis. Apart from neurotoxicity, they are also cardiotoxic as these compounds reduce cardiac conduction, and cause arrhythmias and ventricular fibrillation. These compounds are temperature dependant and are effective at an optimum temperature of 37 degrees centigrade and also work best in the alkaline pH range to exert their neurotoxic and cardiotoxic effects (Wang, 2007).

Conclusion: My hypothesis was supported by the research that Batrachotoxinins are effective avian chemicals that are potent against predators however when the environmental temperature or core body temperature of predators increases beyond 37-degree centigrade, this molecule might not impact them and may not act as a chemical defense mechanism of the genus Pitohui.