Portunus

Portunus is a genus of crabs in the family Portunidae, commonly called swimming crabs. Members are characterized by a broad, flattened carapace and enlarged, flattened hind legs used for swimming, giving them a distinctive paddle-like gait. The genus comprises several species distributed in shallow coastal waters, estuaries, and mangrove ecosystems across the Indo-Pacific, Atlantic, and adjacent regions. Notable species include Portunus pelagicus, the blue swimmer crab; Portunus sanguinolentus, the harlequin crab; and Portunus tritonius, the giant crab. They are opportunistic omnivores, feeding on mollusks, crustaceans, small fish, detritus, and plant matter. Many are active at night or during twilight.

Reproduction involves sexual maturity with distinct sexes; females brood eggs under the abdomen. Larval development passes through free-swimming zoea and nauplius stages before metamorphosis into juvenile crabs.

In taxonomy, Portunus belongs to order Decapoda, class Crustacea. The genus has undergone revisions as molecular and morphological data have clarified relationships within Portunidae; some species formerly placed in Portunus have been reassigned to related genera.

In Roman mythology, Portunus is the god of harbors and ports, protector of docking facilities. The deity is associated with harbor openings and is sometimes connected with the sea-god Neptune in later tradition.