Orchestia agilis Platorchestia platensis is a species of sand flea, an amphipod crustacean that lives on beaches.

[2] There appears to be competitive exclusion between P. platensis and the native Orchestia gammarellus on European beaches.

[2] It was first discovered in northern Europe in 1860 on a beach near Humlebæk, Denmark.

[2] By the 1940s, it was common on both sides of the Kattegat; it reached the Netherlands around 1950, and the United Kingdom in 1978.

[2] Platorchestia platensis was originally described as Orchestia platensis by Henrik Nikolai Krøyer in 1845, based on type material from the Río de la Plata in Uruguay.