Investigating the Neurological Impact of Gambierdiscus Toxin on Fish Behavior in the Florida Keys

For a few weeks now, fish have been swimming in circles in the Florida Keys before they mysteriously died. This abnormal behavior, observed in various fish species, including the endangered smalltooth sawfish, has led to nearly 200 incidents involving over 30 species.

So here is my hypothesis on why the fish are spinning:

Ciguatera fish poisoning (CFP) caused by Gambierdiscus toxins, can lead to neurological symptoms like tingling, numbness, and reversal of hot and cold sensations. Severe cases may cause neurological complications such as weakness, ataxia, and even paralysis, which may result in fish spinning in circles due to loss of coordination and control over their movements.

Ciguatoxins are complex polyether compounds, which are commonly found in tropical and subtropical marine environments such as the Florida Keys. These toxins are bioaccumulated and biotransformed through marine food webs, ultimately reaching higher trophic levels, including reef fish commonly consumed by humans.

Chemically, ciguatoxins consist of multiple cyclic ether rings with lots of different functional groups. They primarily act by binding to and modulating voltage-gated sodium channels (VGSCs) in excitable cells, such as neurons and muscle cells. This interaction disrupts the normal function of VGSCs, leading to differences in action potential generation and propagation, which refers to the process by which action potentials, or electrical signals, travel along the length of a neuron’s axon. When an action potential is initiated at the axon hillock (the junction between the cell body and the axon), it triggers a wave of depolarization that travels down the axon to the axon terminals. This process is triggered by the opening and closing of voltage-gated ion channels along the axon membrane.

In simple terms, propagation allows nerve cells to transmit electrical signals over long distances, which enables communication within the nervous system. It ensures that signals generated at one part of the neuron can be transmitted to other neurons or to target tissues, which allows for coordinated responses throughout the body.

Ciguatoxins additionally exhibit a high degree of potency, with effects observed at extremely low concentrations. They are heat-stable, meaning they remain toxic even after cooking, and there is currently no effective antidote or treatment for CFP.

So what?

When ciguatoxins enter the body, they mess up the way nerve cells send signals to muscles. Imagine nerve signals like messages traveling along a wire. Ciguatoxins basically cut the wire, so the messages can’t get through properly. This leads to paralysis, where muscles can’t move like they should. When the ciguatoxins disrupt the nerve signals that control muscles in fish, it can lead to a loss of coordination and control over their movements. This can cause the fish to swim in circles because they can’t properly direct their swimming motion. It’s like they’ve lost their ability to navigate straight, so they end up going in circles instead.