Pinnoctopus macropus
Nocturnal octopus that feeds among branching corals.
The Atlantic white-spotted octopus, also called the grass octopus or grass scuttle, is a species found in shallow waters across the Mediterranean Sea, the warmer parts of the eastern and western Atlantic, the Caribbean, and the Indo-Pacific. Its mantle reaches about 20 cm (8 in) long, and its total length can be 150 cm (59 in). The first pair of arms are roughly a meter long, much longer than the other three pairs, and all arms are linked by a shallow web. The octopus is red with white blotches on its body and paired white spots on its arms. When disturbed, its color intensifies—a deimatic display that may make it look more threatening to predators.
This octopus lives near shore at depths down to about 17 m (56 ft), favoring sand, rubble, or seagrass meadows, and sometimes buries itself under the sand. Its populations form a species complex spanning the Mediterranean, temperate and tropical Atlantic, Caribbean, and the Pacific and Indian Oceans.
Unlike the common octopus (*Octopus vulgaris*), which feeds during the day, *Pinnoctopus macropus* hunts at night. It moves from one clump of branching coral—often *Acropora* or *Stylophora*—to another, wrapping its mantle around a coral head and probing among the branches with its arms to flush out small fish and invertebrates. Several groupers and other predatory fish often follow it while it feeds, snatching prey that escape the coral.
For a long time, its breeding habits were unknown. Then a female was observed attaching short-stalked eggs, each about 4 by 1.2 mm (0.16 by 0.05 in), to a hard surface in a sheet. She brooded them, aerating and cleaning them, but stopped eating once the eggs were laid and died shortly after they hatched—a common pattern among octopuses. The planktonic larvae that emerged were about 5.5 mm (0.2 in) long, with short arms bearing seven suckers, and fed on zooplankton like crustacean larvae.
Quick Facts
- Genus
- Pinnoctopus
- Species
- macropus
Facts from the source article.
Lore & Background
Pinnoctopus macropus grows to a mantle length of 20 cm with a total length of 150 cm. The first pair of arms are a metre or so long, much longer than the remaining three pairs, and all arms are connected by a shallow web. Its body is red with white blotches, and paired white spots appear on its arms. When disturbed, its color becomes more intense, a deimatic behavior that may make it appear threatening to potential predators.
This octopus lives near the shore at depths down to about 17 m, favoring sand, rubble, or seagrass meadows, and sometimes buries itself under the sand. It feeds by night, moving from one clump of branching coral to another—often Acropora or Stylophora spp.—wrapping its mantle around a coral head and probing with its arms for small fish and invertebrates. Groupers and other predatory fish associate with it while feeding, pouncing on organisms flushed from the coral.
For many years, the breeding habits were unknown. A female was later observed attaching short-stalked eggs (4 by 1.2 mm) to a hard surface, forming a sheet. She brooded the eggs, aerating and cleaning them, stopped feeding when the eggs were laid, and died soon after they hatched. The planktonic larvae were about 5.5 mm long with short, seven-suckered arms and fed on zooplankton such as crustacean larvae.
Reader's Guide
Pinnoctopus macropus is notable for its more fastidious diet compared to the common octopus (Octopus vulgaris), with which it shares some range. While Octopus vulgaris feeds by day, Pinnoctopus macropus feeds by night, using a specialized method of wrapping its mantle around coral heads and probing among branches. This behavior attracts groupers and other predatory fish that capitalize on the small organisms flushed out, indicating a commensal relationship. The species' deimatic color change when disturbed is a key defensive trait. Its breeding biology, once unknown, was documented through observation of a female brooding eggs on a hard surface, ceasing feeding, and dying after hatching—a pattern common among octopuses. The planktonic larvae, feeding on zooplankton, represent the early life stage. The species forms a species complex across the Mediterranean Sea, temperate and tropical Atlantic Ocean, Caribbean Sea, and Pacific and Indian Oceans, living in shallow nearshore habitats like sand, rubble, and seagrass meadows. Its presence in both Atlantic and Indo-Pacific waters highlights a broad distribution, though the article notes it forms a species complex, implying taxonomic uncertainty.
Did You Know?
- Pinnoctopus macropus has a total length of 150 cm (59 in) and a mantle length of 20 cm (8 in).
- Its first pair of arms are about a metre long, much longer than the other three pairs.
- When disturbed, its red body with white blotches becomes more intense as deimatic behavior.
- A female was observed attaching eggs measuring 4 by 1.2 mm to a hard surface, then brooding them until hatching.
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