FISHY TOXINS!

Tavishi

I had written like half a blog post but scrapped it because it didn't feel right, but I was on the phone with Nandini Goel and I was having writer's block (actually I have too many ideas and I can't bring any to life because of decision paralysis).

She kept throwing out ideas and she wanted me to write about stingrays, and then the octopus from Finding Nemo.

Anyways, I decided to sorta indulge Nandini by talking about the way stingray and octopus toxins work.

BLUE-RINGED OCTOPUS

Of course I have to start with the blue animal. Fun fact: blue is my favorite color. If you can't tell from the hair.

Anyways, blue-ringed octopuses are four highly venomous species known for their iridescent rings and aposematism. Their rings change color and flash when they are threatened.

The four species of blue-ringed octopuses are:

1. Greater blue-ringed octopus

2. Southern blue-ringed octopus

3. Blue-lined octopus

4. and a secret fourth option that is poorly described..

All of these octopuses belong to the genus Hapalochlaena, and are quite small, with individuals reaching sizes of only around 8 cm. Their size is not proportionate to the amount of damage they can do, however, with the capability to kill over twenty humans in a matter of minutes.

Blue-ringed octopus venom is produced in the salivary glands by symbiotic bacteria; bacteria genuses include Alteromonas, Vibrio, and Bacillus spp. Toxicity generally begins when someone is bitten by an octopus (octopuses do, contrary to popular belief, have little beaks that are very sharp). However, the toxin has been found throughout the rest of the octopus body, and being in contact with the individual in any way may result in envenomation.

The venom of a blue-ringed octopus has many components, including histamine, hyaluronidase (both of which are likely used to allow toxin to disperse in body), dopamine, etc.

The chief component of venom is tetrodotoxin (TTX). TTX is produced in the muscles and skin upon visual recognition or physical contact with a potential threat; it acts by blocking voltage-gated sodium channels, resulting in muscle paralysis.

The voltage-gated sodium channel is essential to intiate the propagation of an action potential throughout the body, as the initial depolarization starting an action potential results in the opening of voltage-gated sodium channels.

Tetrodoxin prevents the sodium influx, and thus the action potential from spreading. This means no nerve signals, resulting in the characteristic numbness and paralysis associated with octopus toxin.

Tetrodotoxin is associated more commonly with pufferfish and newts, and wasn't originally associated with the blue-ringed octopus at all!

BLUE-SPOTTED STINGRAY

Fun fact: blue is my favorite color! Anyways, the blue-spotted stingray is one of the most venomous species of stingray, and is also one of the most commonly kept in captivity. Isn't that ironic?

Stingrays deliver venom via the spinal blade, which is kinda like a serrated blade (think ouchie venom comb) composed of the protein vasodentin. Vasodentin is a form of the tissue dentin, which composes the teeth. Unlike the dentin found in our teeth, vasodentin is vascularized and has little capillaries in it.

Stingrays release barbs when they feel threatened. These are found near the base of the tail, and venom is produced in tissue found beneath the spinal blade in the tail.

Blue-spotted stingray venom has been found to have a few key components:

• GALECTIN

• PEROXIREDOXIN-6

• CYSTATIN

GALECTIN is a type of carbohydrate-binding protein found widely among venoms. Galectin's role in causing damage is causing apoptosis, or programmed cell death. Galectin thus induces tissue death near area of envenomation, which is, well, bad. There are many types of galectin (galectin-1, galectin-3, galectin-9), but most have apoptotic functions. For example, binding to proteins like CD7 and CD43 on the cell surface. In turn, these proteins activate proteins like caspases, which are the chief inducers of apoptotic processes within cells.

PEROXIREDOXIN-6 (PRDX6) is an antioxidant protein known for activating phospholipase A2 (PLA2), which is known to break down lipids. PRDX6's antioxidant properties include the control of cytokine-induced peroxides. Potential functions in venom thus include breaking down cell membranes. We don't fully understand how this one works, as its inhibition can also lead to cancerous cell growth. PRDX6 remains an enigma..

Finally, CYSTATIN inhibits cysteine proteinases, which, as the name suggests, break down proteins. Some notable cysteine proteases include papains and cathepsins. Cathepsin is notable in this venom's mechanism of action because of its role in clotting. Cathepsin binds to annexin-2, which is a cell-surface receptor for proteins like plasminogen and plasmin. Thus, cystatin might cause inhibition of blood clotting.

this was a really bad post but i'm sleep and exhaustionmaxxing. trust more quality content coming soon.