THE ANIMAL FILES

Swordfish

Xiphias gladius

A slashing bill works alongside locally warmed eyes.

A swordfish combines an elongated bill with specialised warming near its eyes and a daily movement pattern through the water.[1]

Follow the evidence ↓
Swordfish
Image: vtzanatos · Commons · CC BY-SA 4.0
A bill used against prey
The bill can slash prey[1]
Warmth near the eyes
Local eye and brain warming[1]
Moving between water layers
Feeding includes fish and squid[1]

A bill used against prey

Swordfish slash larger prey with the bill and swallow smaller items whole, rather than routinely skewering prey on its tip.[1]

Warmth near the eyes

Specialised tissue near the eyes warms the eyes and brain relative to surrounding water, supporting vision. This local heating does not make every part of the body uniformly warm.[1]

Moving between water layers

Swordfish eat fish and squid and often move toward upper waters to feed at night. During the day they can occur deeper.[1]

A COMMON MIX-UP

Does local warming make its whole body uniformly warm?

No. The described adaptation is concentrated near the eyes and brain. Its location matters as much as the presence of heat.[1]

TRY A LITTLE REASONING

Why is a pointed bill insufficient evidence of habitual spearing?

Reveal the explanation

Function depends on observed movement and feeding sequences. Slashing and spearing use the bill in different ways.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Swordfish (cited revision)
  2. NCBI Taxonomy — Xiphias gladius

Last fact check: