Charybdis Japonica

Charybdis japonica, known as the Asian paddle crab, carries a hexagonal, concave carapace roughly 12 centimeters (4.7 inches) wide, colored a distinctive pale green to olive green across the whole body.

The species belongs to the swimming crab family Portunidae, within the order Decapoda and class Malacostraca. Its striking coloration and shell shape make it one of the more recognizable members of its family, and its mythological namesake gives it a cultural footnote that few crabs share.

The single clearest field mark is the carapace itself: hexagonal in outline, distinctly concave, and colored a uniform pale green to olive green over the whole animal.

The carapace reaches about 12 centimeters (4.7 inches) across, a size that places it among the more substantial swimming crabs in its family. The hexagonal shape, rather than the more rounded or fan-like outlines seen in many other crabs, is itself a useful clue when comparing it to relatives within Portunidae.

No further details on sex, age, or seasonal variation in coloration or shell shape are available from the current evidence.

Observation records for Charybdis japonica show activity across every month of the year, with a clear peak in July, when reported sightings reach 259, well above the yearly average. Secondary highs appear in May (150) and September (144), while the lowest counts come in February (28) and December (55).

This pattern suggests stronger seasonal presence in the warmer months, particularly midsummer, though the data reflect only where and when the species has been observed, not its full range or actual population size. GBIF-style occurrence counts of this kind are presence records, not measures of abundance, and they should be read with that caution in mind.

The genus name Charybdis draws directly on Greek mythology, where Charybdis was a sea monster paired with Scylla, together forming a legendary hazard that challenged epic heroes such as Odysseus. The phrase describing a choice

1. Charybdis japonica carries the name of a sea monster from Greek mythology, Charybdis, who along with Scylla threatened sailors passing through narrow straits.
2. The crab was first described by A. Milne-Edwards in 1861, giving it a scientific record spanning more than 160 years.
3. Its carapace is roughly hexagonal in outline and noticeably concave, reaching about 12 centimeters (4.7 inches) across in adults.
4. Coloring ranges from pale green to olive green over the whole body, a shade that likely helps it blend into shallow coastal habitats.
5. As a member of the family Portunidae, it belongs to the group commonly known as swimming crabs, distinguished by paddle-like hind legs adapted for moving through water.