- Some release toxins called holothurin and holotoxin while alive, and after death. These toxins are particularly fatal to fish, but from observations by aquarists it appears invertebrates such as snails, hermit crabs, shrimps and lobsters don't seem to be affected.
- Some eject strong, thick or thin, very sticky white or blue-white filamentous threads (Cuvierian tubules) on the slightest provocation, which other animals get trapped in, is quite difficult to remove, and may or may not contain toxins. Once we had a situation where a Stubborn Sea Cucumber (Holothuria pervicax) did this in our invertebrate holding tank, resulting in all the hermit crabs getting caught and tangled up in it. To save them we had to pain stakingly, with tweezers, pull the stuff off each hermit crab. This did the trick, but it was an extremely difficult and time consuming task, and some just couldn't be saved.
- Some will eject all of their internal organs through the anus, called auto-evisceration, presumably to distract a predator while it makes its get away. The ejected organs take up to several months to regrow, and while doing so the cucumber cannot feed, but it may absorb some nutrients through the skin.
- They can goopify their bodies to crawl into even very small spaces for protection, then salitify their skin to prevent extraction. Because of this trait, cucumbers can potentially plug up drain or overflow pipes.
- By sweeping the surrounding water, capturing bits of food (plankton) with mucus producing cells on their feeding tentacles, which are then transferred one by one to its mouth to wipe off the food.
- By burrowing into and ingesting the sediment, digesting what is edible from it, then excreting the rest. Cucumbers with this type of feeding technique make good sand stirrers and substrate cleaners. Dirty sediment goes in, clean sediment comes out. Sea cucumbers in this feeding category can often be picky eaters, because some feed only on fine sand, while others prefer course sand. Therefore, if the proper type of sediment a particular sea cucumber needs is not provided, it may not feed.
Family
Cucumariidae
| Holothuriidae
Stichopodidae
| Synaptidae
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