THE ANIMAL FILES

Brook lamprey

Lampetra planeri

Teeth appear just when eating ends.

The brook lamprey overturns an easy assumption about lampreys: this species has no parasitic adult phase. Its young spend years filtering food from a streambed, while adults are devoted to reproduction. The contrast makes its mouth an especially interesting structure, because its use changes along with the animal’s life stage.[1]

Follow the evidence ↓
Brook lamprey
Image: Ra Boe at German Wikipedia · Commons · CC BY-SA 3.0
Adult feeding
Adults do not feed during spawning[1]
Young habitat
Soft streambed sediment[1]
Mouth form
A jawless circular oral disc[1]

A long body without paired fins

Brook lampreys have elongated bodies, no paired fins and a circular oral disc instead of jaws. Gill openings form a row on either side behind the eyes.[1]

Years spent partly hidden in sediment

The larvae bury in soft sediment with the mouth exposed and filter detritus and other organic material. They remain in this stage for several years before transforming.[1]

A mouth repurposed for nest work

During metamorphosis the eyes and oral disc develop while the intestine loses feeding function. Adults move small stones with their mouths and fan particles with their tails when creating spawning pits. Teeth therefore remain useful without implying an adult meal: gripping nest material is a different task from feeding.[1]

A COMMON MIX-UP

Are all adult lampreys parasites?

No. The brook lamprey has no parasitic phase and does not feed as a spawning adult. Its life history cannot be inferred from the more familiar feeding behaviour of some other lamprey species.[1]

TRY A LITTLE REASONING

What can teeth do in an animal that is not eating?

Reveal the explanation

They can grip stones during nest construction. Structure and diet are related but not interchangeable clues; observing how the mouth is used gives a better explanation than assuming every toothed mouth must currently be feeding.[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 — Brook lamprey (fixed revision; adapted and translated)
  2. NCBI Taxonomy — Lampetra planeri (identity and classification)

Last fact check:

One discovery leads to another

Sea lampreyA filter-feeding youngster becomes a fish-attaching adult.Petromyzon marinus ↗Spiny dogfishA shark’s spines are not its teeth.Squalus acanthias ↗Blue sharkBlue above, pale below: an ocean swimmer has more than one colour.Prionace glauca ↗