Four new octopus species of the Octopus macropus group (Cephalopoda: Octopodidae) from the Great Barrier Reef, Australia

Abstract

Four new species of shallow-water octopuses are described from tropical waters of the Great Barrier Reef, Australia. All four are members of the "Octopus macropus group" (Robson. 1929), characterised by arms of unequal length with the dorsal pair longest (AF 1.2.3.4), moderate to high gill lamellae counts (10-14 per demibranch) and a robust conical copulatory organ. All are nocturnally active. Two species, O. alpheus and O. aspilosomatis spp. nov., occur in clear waters foraging predominantly on intertidal coral reefs and offshore islands. O. dierythraeus sp. nov. forages intertidally and subtidally on muddy substrates in coastal waters. Octopus graaptus occurs in more open waters, on sandy and mud substrata in the channels and flat bottoms between islands. Full morphological descriptions are provided, along with details of known distributions, life history and commercial exploitation. Delineation of each species from related taxa is discussed.