# Freeloader Fish (DD-453)

> Juvenile trevally and some filefish shelter in or beneath jellyfish bells, using the stinging tentacles as a shield against predators and picking off food the jellyfish has caught or nibbling its tissue, the Reel says. It describes the relationship as commensalism, in which the fish benefit and the jellyfish is largely unaffected. The footage, credited to elevatedmoments.co, shows small fish swimming inside a jellyfish.

- Department: Nature
- First published: 2025-01-10
- Last updated: 2025-01-10
- Permalink: https://detailenjoyer.com/case/freeloader-fish/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-453-F01**: Juvenile trevally and filefish. _(Write-up · Exhibit A (Fish))_
- **DD-453-F02**: Inside the bell. _(Write-up · Exhibit B (Shelter))_

## Write-up

Some young fish hide inside a jellyfish's bell. The stinging tentacles keep predators away.

1. **Fish**: Juvenile trevally and filefish.
2. **Shelter**: Inside the bell.
3. **Defense**: Stinging tentacles.
4. **Food**: Scavenged prey.
5. **Relationship**: Commensalism, per the Reel.

## Related case files

- [Flaming Jellies (DD-308)](https://detailenjoyer.com/case/flaming-jellies/): I linked the jellyfish they live with

## Reel vs. record

- **Note**: The Reel calls the fish immune to the venom; they are generally thought to tolerate or avoid the stings rather than be fully immune.

## Video: Freeloader Fish: Some Young Fish Hide Inside a Jellyfish's Bell

- Duration: 29.9 s · Published: 2025-01-10
- File: https://detailenjoyer.com/assets/videos/DEpvnVKJ5Ut.mp4

### Transcript

Did you know certain fish such as juvenile trevally and some species of filefish are known to swim within the bells of jellyfish for protection and sustenance. These fish use the jellyfish's stinging tentacles as a shield against predators as they are often immune to the jellyfish's venom. Inside the bell, they are also able to scavenge small prey items caught by the jellyfish or feed on the jellyfish's tissue without causing significant harm. This relationship is an example of commensalism, with a fish benefit from the jellyfish's defense mechanisms, while the jellyfish is neither significantly helped nor harmed. NOW YOU KNOW!

## Questions & answers

**Q: Where do the fish hide?**  
A: Jellyfish. _(Source: Write-up · Exhibit A (Fish) · Wikipedia: Commensalism)_

**Q: Which fish?**  
A: Young. _(Source: Write-up · Exhibit B (Shelter) · Wikipedia: Commensalism)_

**Q: What protects them?**  
A: Shield. _(Source: Write-up · Exhibit C (Defense) · Wikipedia: Commensalism)_

**Q: What do they eat?**  
A: Leftovers. _(Source: Write-up · Exhibit D (Food) · Wikipedia: Commensalism)_

**Q: Relationship named?**  
A: One benefits. _(Source: Write-up · Exhibit E (Relationship) · Wikipedia: Commensalism)_

## Sources

- [Wikipedia: Commensalism](https://en.wikipedia.org/wiki/Commensalism)

## Cite this case file

Easterling, Marcus. "Freeloader Fish." The Detail Department (DetailEnjoyer), case file DD-453, last updated Jan 10, 2025. https://detailenjoyer.com/case/freeloader-fish/