What is Meroplankton?

Meroplankton spend only the larval or early stages of their life as part of the plankton and spend their adult lives on the reef. Some, like polychaete worms, will then revisit the plankton during their reproductive stages. Many of the common, well-known animals found on the Great Barrier Reef spend time as free-swimming meroplankton, bearing little or no resemblance to the adult they will become. The differences between the appearance of larval and adult stages led to much confusion in the past when larval forms were often believed to be completely different species from the adults.

While living in the plankton, meroplankton either feed on other members of the plankton, or they live off the yolk they have retained from the egg they hatched from. Larvae spend varying amounts of time in the plankton, from minutes to over a year. However, just how long these tiny animals can be considered truly planktonic is under some debate. Scientists in recent years have discovered that many of these tiny animals in the plankton (in particular larval fish and crustaceans) quickly become very good swimmers capable of incredible feats of speed and endurance.

Meroplankton includes sea urchins, starfish, sea squirts, most of the sea snails and slugs, crabs, lobsters, octopus, marine worms and most reef fishes.


Tube Anemone larva

Tube Anemone larva
Tube Anemone Cerinula Larva Image: Peter Parks/imagequest3d.com, Peter Parks
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Sea Cucumber larva

Sea Cucumber larva
Sea Cucumber larva, Meroplankton Image: Peter Parks/imagequest3d.com, Peter Parks
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Brittle Star larva and Coral Planula

Brittle Star larva and Coral Planula
Brittle Star larva and Coral Planula Image: Peter Parks/imagequest3d.com, Peter Parks
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Octopus larva

Octopus larva
Octopus Larva Image: Peter Parks/imagequest3d.com, Peter Parks
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Cone Shell larva

Cone Shell larva
Gastropod Veliger Larva (Conus) Image: Peter Parks/imagequest3d.com, Peter Parks
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Starfish Larva

Starfish larva
Starfish Larva, Meroplankton. The late stage larva of a starfish shows clearly the yellow/orange rudiment that will be the definitive starfish at metamorphosis. Image: Tim Hellier/imagequest3d.com, Peter Parks
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