# Bathypterois grallator (DD-580)

> Bathypterois grallator, the tripod fish or tripod spiderfish, is a deep-sea fish in the family Ipnopidae. George Brown Goode and Tarleton Bean described it in 1886. It lives on continental slopes and abyssal plains in the Atlantic, Pacific and Indian oceans, roughly between 40°N and 40°S, at depths of 878 to 4,720 m and water temperatures of 2.7 to 13.5 °C. It's the largest member of its genus, commonly over 30 cm long and up to about 43 cm. The lower lobe of its tail fin and both pelvic fins end in greatly elongated rays, up to about a meter long, or roughly three times its body length. When it settles, it lands on its pelvic fins first and then lowers its tail ray, standing on the three like a tripod. The rays are flexible when it swims but stiff when it stands, and researchers have suggested that the fish pumps fluid into them to stiffen them. Standing facing into the current, it waits for food to drift past and uses the tips of its pectoral fins to feel for prey, since its eyesight is very poor. Small tripod fish eat mostly copepods, amphipods and other small crustaceans. Larger ones, above about 24 cm, eat mostly small fish and decapods by weight. Each fish is a simultaneous hermaphrodite and may be able to fertilize its own eggs, which helps where mates are scarce. The IUCN lists it as Least Concern. The footage, credited to the Schmidt Ocean Institute, shows a pale tripod fish drifting and standing on long fin rays over a dark, sandy seafloor.

- Department: Nature
- First published: 2025-05-25
- Last updated: 2025-05-25
- Permalink: https://detailenjoyer.com/case/bathypterois-grallator/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-580-F01**: The tripod fish's fin rays can reach about a meter, roughly three times its body length. _(Write-up · Exhibit A (Three long fin rays))_
- **DD-580-F02**: Bathypterois grallator lives at depths of about 878 to 4,720 m. _(Write-up · Exhibit C (878 to 4,720 m))_

## Write-up

A fish on stilts. The tripod fish stands on the seafloor on fin rays up to a meter long.

1. **Three long fin rays**: Rays on its pelvic fins and tail lobe reach about a meter, roughly three times its body length.
2. **Stiff when standing**: The rays are flexible in swimming but stiff when it stands. It may pump fluid into them.
3. **878 to 4,720 m**: It lives on slopes and abyssal plains of three oceans, from about 40°N to 40°S.
4. **Facing the current**: It stands into the current and feels for drifting prey with its pectoral fins.
5. **Diet grows with size**: Small ones eat crustaceans. Larger ones eat mostly small fish and decapods.

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## Reel vs. record

- **Note**: 'Between 1,000 and 4,700 meters': rounded. Recorded depths run from 878 to 4,720 m.
- **Note**: 'Prey like small crustaceans': true for small fish (copepods, amphipods). Fish above about 24 cm eat mostly small fish and decapods by weight.
- **Note**: 'Elongated fin rays... up to a meter long': correct. They're about three times its body length, which reaches about 43 cm.
- **Missing**: the rays are flexible when it swims but stiff when it stands, possibly because it pumps fluid into them. It feels for prey with its pectoral fins, since its eyesight is very poor.

## Video: Bathypterois grallator: A Fish on Stilts

- Duration: 23.5 s · Published: 2025-05-25
- File: https://detailenjoyer.com/assets/videos/DKGCCiJyUvv.mp4

### Transcript

DID YOU KNOW? The tripod fish is a deep sea species named for its remarkable ability to "stand" on the seafloor, using elongated fin rays from its pelvic and caudal fins, which can extend up to a meter long. Found at depths between 1,000 and 4,700 meters, this fish uses its stationary posture to conserve energy in the low light, low food environment of the abyss, waiting motionless for prey like small crustaceans to drift within reach. NOW YOU KNOW!

## Questions & answers

**Q: How long can the tripod fish's fin rays get?**  
A: Roughly three times its body length. _(Source: Write-up · Exhibit A (Three long fin rays) · Wikipedia: Bathypterois grallator; Davis & Chakrabarty, 'Tripodfish (Aulopiformes: Bathypterois) locomotion and landing behaviour from video observation at bathypelagic depths in the Campos Basin of Brazil', Marine Biology Research (2011))_

**Q: Which fins carry the 'tripod' rays?**  
A: The lower lobe of the tail plus both pelvic fins. _(Source: Write-up · Exhibit A (Three long fin rays) · Wikipedia: Bathypterois grallator; Davis & Chakrabarty, 'Tripodfish (Aulopiformes: Bathypterois) locomotion and landing behaviour from video observation at bathypelagic depths in the Campos Basin of Brazil', Marine Biology Research (2011))_

**Q: What happens to the fin rays when the fish stands?**  
A: It may pump fluid into them. _(Source: Write-up · Exhibit B (Stiff when standing) · Wikipedia: Bathypterois grallator)_

**Q: What is the deepest recorded depth for the tripod fish?**  
A: Its range is about 878 to 4,720 m. _(Source: Write-up · Exhibit C (878 to 4,720 m) · Wikipedia: Bathypterois grallator; FishBase: Bathypterois grallator (Goode & Bean, 1886))_

**Q: How does the tripod fish find prey?**  
A: Its eyesight is very poor. _(Source: Write-up · Exhibit D (Facing the current) · Wikipedia: Bathypterois grallator)_

## Sources

- [Wikipedia: Bathypterois grallator](https://en.wikipedia.org/wiki/Bathypterois_grallator)
- [FishBase: Bathypterois grallator (Goode & Bean, 1886)](https://www.fishbase.se/summary/Bathypterois-grallator.html)
- [Davis & Chakrabarty, 'Tripodfish (Aulopiformes: Bathypterois) locomotion and landing behaviour from video observation at bathypelagic depths in the Campos Basin of Brazil', Marine Biology Research (2011)](https://doi.org/10.1080/17451000.2010.515231)
- [IUCN Red List: Bathypterois grallator (2015)](https://doi.org/10.2305/IUCN.UK.2015-4.RLTS.T194992A15571915.en)

## Cite this case file

Easterling, Marcus. "Bathypterois grallator." The Detail Department (DetailEnjoyer), case file DD-580, last updated May 25, 2025. https://detailenjoyer.com/case/bathypterois-grallator/