THE ANIMAL FILES

Pacific oyster

Magallana gigas

A drifting larva becomes a permanently attached oyster.

The Pacific oyster's life changes dramatically at settlement. Larvae can disperse in currents before attaching to a surface, and adults grow in shapes influenced by their surroundings. Oyster shells themselves can become places for the next generation to settle.[1]

Follow the evidence ↓
Pacific oyster
Image: No machine-readable author provided. BetacommandBot assumed (based on copyright claims). · Commons · CC BY-SA 3.0
A variable shell
Shell form reflects the attachment environment.[1]
Settling among adults
Larvae can settle on adult shells.[1]
The settlement transition
A foot gland produces attachment cement.[1]

A variable shell

The two valves differ in shape and show strong radial folds. Colour and dimensions vary as oysters grow in different positions. A shell is therefore a record of growth in a location, rather than a perfectly repeated mould for every individual.[1]

Settling among adults

Hard surfaces in sheltered or shallow water provide attachment sites. Existing shells can also be used, allowing oysters to accumulate in reef-like masses. The surface is habitat as well as the remains or body covering of another oyster.[1]

The settlement transition

Larvae spend a planktonic period before selecting a settlement site. Cement from a foot gland secures the animal, followed by development into a juvenile spat. Dispersal through the water and permanent attachment belong to successive life stages, not contradictory descriptions of the same moment.[1]

A COMMON MIX-UP

Has an oyster spent its entire life fixed in one spot?

No. Before settlement, its larva has a dispersing planktonic stage.[1]

TRY A LITTLE REASONING

How can an adult shell contribute to the next generation's habitat?

Reveal the explanation

It supplies a hard settlement surface on which larvae can attach.[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 — Pacific oyster (cited revision)
  2. NCBI Taxonomy — Magallana gigas

Last fact check:

One discovery leads to another

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