Describe in detail what a nematocyst does and how it does its job.

A nematocyst is a specialized cell unique to the phylum Cnidaria, which includes marine organisms such as jellyfish, anemones, corals, and hydroids. It functions as a defensive and predatory weapon. A nematocyst is essentially a small, venom-filled sac containing a tightly coiled dart-like structure called a tubule. Here are the detailed steps of how a nematocyst does its job:

1. Triggering: Nematocysts are often concentrated on the tentacles of cnidarians. They are triggered either by physical contact or chemical stimuli. When a prey or predator contacts the tentacle or when certain chemicals are detected, the nematocyst reacts.

2. Inversion: Upon being triggered, the nematocyst fires. This action involves the rapid eversion of the tubule, which turns inside out much like the finger of a glove when it is pushed through itself. This process is exceedingly quick and is one of the fastest biological processes known.

3. Penetration: The everted tubule penetrates the skin of the prey or predator. In many species, the tubule is armed with spines or barbs that help it anchor into the victim's tissue.

4. Envenomation: Once the tubule has penetrated, the venom stored within the nematocyst is pumped through the tubule into the victim. This venom can have various effects, including paralysis, pain, or dissolving of tissues, depending on the species of cnidarian and the type of nematocyst.

5. Anchoring and Reeling: In predatory cnidarians, once the prey has been envenomated, the nematocyst is used to hold onto the victim. Muscle contractions in the tentacles may then reel the prey into the mouth area for ingestion.

6. Recharging: After discharging, a nematocyst cannot fire again and is replaced by new ones produced by the cnidarian.