Range extension of the Regulus seastar Pentaceraster regulus (Müller & Troschel, 1842) (Echinodermata: Asteroidea: Oreasteridae): evidence of tropicalization of the east Australian coast

Abstract

The seastar Pentaceraster regulus (Müller & Troschel, 1842) is documented from the coastal estuary of Wallis Lake, New South Wales, Australia, c. 600 km from the nearest previous records at Lord Howe Island, an offshore area known to receive a tropical influence from the southern flowing East Australian Current, and between 640 to 800 km south of earlier published records from mainland areas to the north in Queensland. Historical data combined with contemporary observations provide evidence that this is a recent range extension and may be a further example of tropicalization of the south eastern Australian coastal waters. Records from Wallis Lake span a twelve year period and the most recent observations in 2020 indicate it is abundant, and there is considerable difference between the smallest and largest specimens present, suggesting a population that completes most or all of the life cycle is established in the estuary. Given the impacts range shifted species and other echinoderms are known to have in influencing ecosystem dynamics, it is suggested that further study of this seastar is prudent to determine what impacts it may have in the newly colonized area.