THE GLOBAL INVADER PALAEMON MACRODACTYLUS (DECAPODA, PALAEMONIDAE): AN INTERROGATION OF RECORDS AND A SYNTHESIS OF DATA

In the latter half of the 20th Century and the early part of the 21st the Asian shrimp species Palaemon macrodactylus began being reported from several world-wide locations. Literature records of Palaemon macrodactylus are herein collated, corroborated through examination of material where possible. Material from each main occupied region has been verified as P. macrodactylus, but records from Taiwan and Darwin do not refer to P. macrodactylus. Some records still require verification in the absence of material examined. The data show that, in most cases, the first occurrence of P. macrodactylus in a region is several years prior to the detection of the species. Biological, ecological and physiological aspects of the species are summarised to gain an understanding of why the species is such a successful invader. However, the factors favouring the introduction of R macrodactylus over other species of Palaemon remain unclear as many traits are shared with other species of the genus. Information on larval tolerances may provide further clues for the success of P. macrodactylus. We hypothesise that the global distribution of the species has been achieved through a combination of at least three primary introductions from Asia and three secondary introductions, but the origin of the Argentinean population remains unclear. Small-scale secondary introductions have likely aided spread within a region. Regions at risk of invasion by P. macrodactylus include the Baltic Sea, southern Norway and South Africa, whilst further spread within occupied, broad regions should be expected.