# Black Widow Venom

How a black widow's venom is made, and how its proteins open calcium doors in a nerve ending to flood a muscle with signals\. Written in English\.

By vivid\-wombat\-2bcf1402

Topic: Nature & Biology

[Open the interactive Jig](https://ask.jig.com/j/ytzPYx5Ar36o)

## Transcript

### 1. Meet the black widow

This shiny spider is a female black widow, shown here far bigger than life\. Her real body is only about a centimetre long, the size of a pea\. She spends her days in a messy, tangled web in quiet, sheltered places like woodpiles and sheds\.

Drag the scene to turn it and look around\.

### 2. The red hourglass

She often hangs upside down, belly up, so the red hourglass on her underside shows\. The mark can be whole or broken into two pieces\. Grown\-up females wear it; males are much smaller and rarely bite\.

### 3. Fangs and venom glands

Venom is a poison an animal injects\. Hers is made in two small glands, shown glowing here, that reach from her jaws back into her front body\. A thin tube leads from each gland to the tip of a tiny fang\.

Many people barely feel the bite itself\.

### 4. A cocktail of proteins

Her venom is a mix of proteins, the busy building blocks of living things\. Five kinds, shown blue, work on insects, her usual food\. The green one works on crabs and their relatives\. The big orange one, alpha\-latrotoxin, works on animals with backbones, including us\.

One alpha\-latrotoxin weighs about as much as 7,000 water molecules\.

### 5. Four pieces make a ring

Now we zoom far in, to the end of a nerve, the wire that carries messages to a muscle\. Alpha\-latrotoxin sticks to the nerve's outer skin, called the membrane\. Four copies join into a ring that pokes right through it\.

This part is an illustration, not to scale\.

### 6. A door for calcium

The ring has a hole in its middle, like a tiny door that will not shut\. Calcium, shown as blue specks, rushes in through it\. Inside a nerve ending, calcium is the signal that says: send the message now\!

### 7. A flood of messages

Nerve endings keep their messages in tiny bubbles called vesicles\. With calcium pouring in, the bubbles empty all at once and the messengers flood across to the muscle\. That is why a bite can bring cramps, aching muscles and sweating\.

Botulinum toxin does the opposite: it stops these messages being sent\.

### 8. Rarely deadly, still respect it

For insects this venom is a knockout, but for people it is rarely deadly\. US poison centres recorded over 23,000 black widow bites from 2000 to 2008, with no deaths\. Black widows are shy and bite mostly when pressed against skin, so wear gloves in woodpiles and get medical advice after a bite\.

Doctors can ease the pain, and an antivenom exists\.